EP4704964A2 - Tapered drug delivery, optical stimulation, and electrophysiology probe for neural interfacing - Google Patents

Abstract

Multi-modal fiber probe devices and processes for fabricating the same are described. In one example, a multi-modal fiber probe device can include a flexible tapered fiber probe structure having a micro-scale tip region at a first end and a macro-scale connector region at a second end opposite the first end. The multi-modal fiber probe device can further include an optical waveguide positioned in and extending through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region. The multi-modal fiber probe device can further include a microfluidic channel formed in and extending through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region.

Description

Attorney Docket: 222204-2920 TAPERED DRUG DELIVERY, OPTICAL STIMULATION, AND ELECTROPHYSIOLOGY PROBE FOR NEURAL INTERFACING GOVERNMENT LICENSE RIGHTS [0001] This invention was made with government support under grant number R01NS123069A awarded by the National Institutes of Health (NIH) and grant number R21EY033080A awarded by the NIH. The government has certain rights in the invention. CROSS REFERENCE TO RELATED APPLICATIONS [0002] This application claims the benefit of and priority to U.S. Provisional Application Serial No. 63/499,869, filed May 3, 2023, titled “TAPERED DRUG DELIVERY, OPTICAL STIMULATION, AND ELECTROPHYSIOLOGY PROBE FOR NEURAL INTERFACING” the entire contents of which are hereby incorporated herein by reference. This application further claims the benefit of and priority to U.S. Provisional Application Serial No.63/598,801, filed November 14, 2023, titled “TAPERED DRUG DELIVERY, OPTICAL STIMULATION, ELECTROPHYSIOLOGY PROBE, AND FABRICATION THEREOF” the entire contents of which are hereby incorporated herein by reference. This application further claims the benefit of and priority to U.S. Provisional Application Serial No. 63/598,810, filed November 14, 2023, titled “COMBINED FIBER PHOTOMETRY AND ELECTROPHYSIOLOGY PROBE AND FABRICATION THEREOF” the entire contents of which are hereby incorporated herein by reference. BACKGROUND [0003] Our nervous system plays a crucial role in every aspect of our lives, from thoughts and emotions to sensations and respiration. Advancement in technology has furthered our understanding of the nervous system, and a greater insight into the brain’s inner workings is necessary for earlier detection and treatment of neurological disorders such as Alzheimer’s disease, epilepsy, and substance use disorders as well as advancement of brain-machine interfaces that can restore sensorimotor functions. Monitoring and manipulating neural activity with increased precision enables a deeper understanding of dynamics of the nervous system. The widespread adoption of silicon-based neural probe devices that are able to monitor electrical activity and apply light has enabled great progress in this realm. Attorney Docket: 222204-2920 [0004] Understanding the neural basis of behavior and the diagnosis and curing of neurological diseases require carefully designed, highly specific protocols that monitor and manipulate combinations of physiological elements and their interactions in behaving animals to unlock the brain’s complex and obscure mechanisms. The principal tool for such investigation is the neural probe. Currently, the most widely available probes are general use silicon-based micro- electromechanical systems (MEMS) devices. Additionally, electrophysiology is a mature and well understood method of monitoring neural activity with high temporal frequency. Further, fiber photometry involves collecting and analyzing optical signals emitted from neurons affected by genetically encoded calcium indicators (GECIs). SUMMARY [0005] The present disclosure is directed to multi-modal fiber probe devices and processes for fabricating the same. Embodiments herein describe thermal tapering processes that can be implemented to fabricate a various types of flexible multi-modal fiber neural probe devices that each combine ultrafine features of dense electrodes or tetrodes, optical waveguides, and microfluidic channels at a tip region of the device. The probe devices of the present disclosure can each also include a backend connector region that can allow for scalable assembly of the probe. [0006] Aspects and advantages of embodiments of the present disclosure will be set forth in part in the following description or can be learned from the description or through practice of the embodiments. Other aspects and advantages of embodiments of the present disclosure will become better understood with reference to the appended claims and the accompanying drawings, all of which are incorporated in and constitute a part of this specification. The drawings illustrate example embodiments of the present disclosure and, together with the description, serve to explain the related concepts of the present disclosure. [0007] According to one example embodiment, a multi-modal fiber probe device can include a flexible tapered fiber probe structure having a micro-scale tip region at a first end and a macro-scale connector region at a second end opposite the first end. The multi-modal fiber probe device can further include an optical waveguide positioned in and extending through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region. The multi-modal fiber probe device can further include a microfluidic channel formed in and extending through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region. Attorney Docket: 222204-2920 BRIEF DESCRIPTION OF THE DRAWINGS [0008] Many aspects of the present disclosure can be better understood with reference to the following figures. The components in the figures are not necessarily to scale, with emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, repeated use of reference characters or numerals in the figures is intended to represent the same or analogous features, elements, or operations across different figures. Repeated description of such repeated reference characters or numerals is omitted for brevity. [0009] FIG. 1 illustrates a perspective view of an example multi-modal fiber probe device according to various aspects and embodiments of the present disclosure. [0010] FIGS.2A, 2B, and 2C illustrate example probe component arrangements of an example multi-modal fiber probe device according to various aspects and embodiments of the present disclosure. [0011] FIGS. 3A, 3B, and 3C illustrate example optical waveguide addressability modes of an example multi-modal fiber probe device according to various aspects and embodiments of the present disclosure. [0012] FIG.4A illustrates an example preform fabrication process according to various aspects and embodiments of the present disclosure. [0013] FIG.4B illustrates an example thermal drawing process according to various aspects and embodiments of the present disclosure. [0014] FIG.4C illustrates an example thermal tapering process according to various aspects and embodiments of the present disclosure. [0015] FIG.4D illustrates an example backend connection process according to various aspects and embodiments of the present disclosure. [0016] FIGS. 5A, 5B, and 5C illustrate various views of another example multi-modal fiber probe device according to various aspects and embodiments of the present disclosure. [0017] FIG.6A and 6B illustrate additional example probe component arrangements of another example multi-modal fiber probe device according to various aspects and embodiments of the present disclosure. [0018] FIG. 7A illustrates another example preform fabrication process according to various aspects and embodiments of the present disclosure. [0019] FIG. 7B illustrates another example thermal drawing process according to various aspects and embodiments of the present disclosure. Attorney Docket: 222204-2920 [0020] FIG. 7C illustrates another example thermal tapering process according to various aspects and embodiments of the present disclosure. [0021] FIG. 7D illustrates another example backend connection process according to various aspects and embodiments of the present disclosure. [0022] FIGS. 8A and 8B illustrate views of another example multi-modal fiber probe device according to various aspects and embodiments of the present disclosure. [0023] FIGS. 9A and 9B illustrate views of another example multi-modal fiber probe device according to various aspects and embodiments of the present disclosure. [0024] FIG. 10 illustrates an example fabricated multi-modal fiber probe device according to various aspects and embodiments of the present disclosure. [0025] FIGS.11A and 11B illustrate example implementations of the example multi-modal fiber probe device of FIG.10 according to various aspects and embodiments of the present disclosure. [0026] FIGS.12A and 12B illustrate additional example implementations of the example multi- modal fiber probe device of FIG. 10 according to various aspects and embodiments of the present disclosure. [0027] FIG. 13 illustrates another example fabricated multi-modal fiber probe device and an example implementation thereof according to various aspects and embodiments of the present disclosure. DETAILED DESCRIPTION [0028] Understanding the neural basis of behavior requires monitoring and manipulating combinations of physiological elements and their interactions in behaving animals. As noted above, the widespread adoption of silicon-based neural probe devices that are able to monitor electrical activity and apply light has enabled great progress in the monitoring and manipulation of neural activity. However, a problem with such existing probe devices is that other biological factors, such as neurochemistry, are intertwined with electrical activity, necessitating simultaneous investigations, which is not practical with such probe devices. [0029] Another problem with existing silicon-based neural probe devices is that the fabrication of these probes is time consuming and expensive. As such, a thermal fiber drawing technique is often employed to produce scalable fiber devices. Such fiber devices are fabricated using a method commonly used in industry to produce optical fibers. Specifically, a macro-scale, multi-material preform is heated until softened, and pulled into hundreds of meters of fibers that can be as thin as a human hair. This fast and simple fabrication process utilizes affordable machinery and soft material, Attorney Docket: 222204-2920 resulting in a cheap, sturdy, and biocompatible device. The thermal drawing process is therefore promising. However, a problem with the fiber devices produced from such a thermal drawing process is that the backend connection of micrometer fibers presents a major challenge that limits the fiber’s practicality in neural applications. [0030] The present disclosure provides solutions to address the above-described problems associated with monitoring and manipulating neural activity in general and with respect to the existing neural probes described above. To overcome such limitations, examples of the present disclosure include multi-modal neural fiber probe devices that can interact with the brain of mammals across multiple modalities. The multi-modal neural fiber probe devices can be embodied as polymer- based fiber probe devices, referred to herein as a Tapered, Drug delivery, Optical stimulation, and Electrophysiology (T-DOpE) probe devices. In addition, some examples include a thermal tapering process that can be implemented to fabricate the multi-modal neural fiber probe devices. Further, examples include a backend connector region of multi-modal neural fiber probe devices that can be approximately 10 to 30 times (e.g., 20 times) larger than connector regions of existing fiber neural probes. [0031] The T-DOpE probe devices and the thermal tapering processes provide several technical benefits and advantages. For example, an example T-DOpE probe device can be embodied as a single neuron-scale device that can achieve high-fidelity electrophysiological recording, focal drug delivery, and optical stimulation. The T-DOpE probe device allows for the investigation of highly complex neural circuitry, such as the hippocampus of behaving mice. The T-DOpE probe device can include a tapered geometry and a relatively small and/or angled tip (e.g., as small as 50 micrometers (μm)) that can allow for minimal tissue damage. Additionally, the T-DOpE probe device can include a relatively large backend connector region (e.g., approximately 20 times larger compared to existing fiber based neural probes) that can allow for scalable assembly of the T-DOpE probe device and its direct integration with industrial-level connectors. Further, the thermal tapering process can be implemented to fabricate the T-DOpE probe device and/or the backend connection in a relatively fast and inexpensive manner. [0032] In addition, a backend connection process described herein and the backend connector region of the T-DOpE probe device allow for the fabrication of microprobe designs with higher complexities, while increasing the backend connection scalability. For instance, the backend connection process and the backend connector region of the T-DOpE probe device can allow for a semi-automated connection process, thereby reducing connection time, labor, and cost. Further, existing fiber based neural probe devices and connection processes only allow for connections to the Attorney Docket: 222204-2920 outer layers of the device. In many conventional devices and processes, it is still difficult or impossible to connect the channels near the center of the device without damaging the outer channels. This restricts the complexity of such existing devices. In contrast, the backend connection process and the backend connector region of the T-DOpE probe devices described herein allows for electrical, optical, and chemical modalities in the entirety of the device to be easily connected, thereby allowing for scalable manufacturing and distribution of the T-DOpE probe device of the present disclosure. [0033] Electrophysiology is a mature and well understood method of monitoring neural activity with high temporal frequency. However, its spatial resolution is relatively poor. Due to the mostly extracellular nature of the electrical recordings, it is difficult to differentiate the signals from different neurons, with the process often requiring considerable post recording signal processing. In contrast, fiber photometry involves collecting and analyzing optical signals emitted from neurons affected by genetically encoded calcium indicators (GECIs). GECIs can be engineered to respond to or emit different wavelengths of light and bind to neurotransmitters with high specificity. This, combined with transgenesis or viral infection, which allows GECIs to affect specific brain regions and cell types, results in fiber photometry possessing high spatial resolution. However, due to the inherent randomness of photon emission and detection, fiber photometry suffers from poor temporal resolution. [0034] The present disclosure also provides solutions to address the above-described problems associated with electrophysiology and fiber photometry with respect to the existing devices and methods. To overcome such limitations, some examples of the present disclosure describe a multi- modal neural fiber probe device that can simultaneously perform electrophysiology and fiber photometry operations, and some examples describe a convergence thermal tapering break method for fabricating such a device. The multi-modal neural fiber probe device can be embodied as a fiber probe device referred to herein as a fiber Photometry, Drug delivery, Optical stimulation, and Electrophysiology (P-DOpE) probe device. [0035] The simultaneous electrophysiology and photometry applications that are facilitated by the P-DOpE probe devices enable cross-referencing of electrical and optical signals, resulting in high spatial and temporal resolution that be leveraged by researchers to study heretofore difficult questions. The P-DOpE probe devices described herein include high spatial and high temporal resolutions and are capable of detecting both electrical and chemical signals concurrently (e.g., simultaneously). The P-DOpE probe devices are relatively inexpensive probes that are capable of both electrophysiology and fiber photometry, and the convergence thermal tapering break method allows for rapid easy backend connection without the bulky backend that comes with other tapering Attorney Docket: 222204-2920 methods. Additionally, similar to a convergence thermal tapering method that can be used to fabricate the T-DOpE probed devices described herein, the convergence thermal tapering break method is also a modular fabrication process and thus allows for rapid cost-effective device customization tailored to a multitude of unique requirements. [0036] Hippocampal circuit activity is critical for episodic and spatial memory. Hippocampal theta (~6-10 Hertz (Hz)), gamma (~35-80 Hz), and sharp wave-ripple (SPW-R, ~100-250 Hz) oscillations all contribute to mnemonic functions of the circuitry. In rodents, these oscillations are disrupted following systemic pharmacological activation of cannabinoid receptors by compounds such as ǻ-9-tetrahydrocannabinol (ǻ9-THC) or agonists of cannabinoid receptors (CB1Rs). This is suggested to be a mechanism behind cannabinoid-associated memory impairment in rodents and humans. It is believed that activation of CB1Rs impairs memory by changing the activity of hippocampal neurons expressing CB1Rs as well as their synaptic partners in local hippocampal circuits. [0037] The synthetic cannabinoid, CP-55,940, is a useful tool to study the effect of CB1R activation in rodent models. Previously, it has been shown systemic administration of CP-55,940 in rats most prominently reduces theta oscillations and SPW-Rs. Importantly, systemic administration of cannabinoids cannot rule out CA1 interactions with other brain areas. The same study also found that in urethane-anesthetized rats, intrahippocampal delivery of CP-55,940 abolished SPW-Rs, suggesting that the effects of systemic administration may be mediated by intra-hippocampal changes in CB1R signaling. The effect of focal CA1 CB1R agonism has never been investigated in behaving animals, and because the only intrahippocampal administration was completed under anesthesia, the neuronal substrates and mechanisms by which CB1Rs control hippocampal rhythms remains unknown. By using the T-DOpE probe devices described herein, investigation of the role of CA1 CB1Rs in hippocampal local field potential activity can be achieved using simultaneous optogenetic manipulation of CA1 neuron excitability and CB1R agonism via pharmacological intervention. [0038] Acute and chronic implantation of a T-DOpE probe device in a mouse hippocampus CA1 revealed canonical neuronal activity at the level of local field potentials and spiking. Taking advantage of the triple-functionality of the T-DOpE probe device, local field potentials were monitored with simultaneous manipulation of endogenous type 1 cannabinoid receptors (CB1R; via microfluidic agonist delivery) and CA1 pyramidal cell membrane potential (optogenetic activation). Electro-pharmacological experiments revealed that focal infusion of CB1R agonist CP-55,940 in dorsal CA1 downregulated theta and sharp wave-ripple oscillations. Furthermore, using the full electro-pharmacological-optical feature set of the T-DOpE probe device, it was determined that Attorney Docket: 222204-2920 CB1R activation reduces sharp wave-ripples (SPW-Rs) by impairing the innate SPW-R-generating ability of the CA1 circuit. Among others, these are just some examples of the applications for the T- DOpE probe devices described herein. [0039] For context, FIG.1 illustrates a perspective view of an example multi-modal fiber probe device 100 (or “probe device 100”) according to various aspects and embodiments of the present disclosure. The probe device 100 can be designed, embodied, and implemented as a flexible, multi- modal neural fiber probe device according to the examples described herein. For instance, the probe device 100 can be designed, embodied, and implemented as a Tapered Drug delivery, Optical stimulation, and Electrophysiology (T-DOpE) probe device as described herein. The probe device 100 offers relatively higher complexities at a tip region compared to existing fiber based probe devices while also easing the connection between a backend connector region and external electronics that may be coupled to the probe device 100. [0040] The probe device 100 illustrated in FIG. 1 includes a tapered fiber probe structure 110. The tapered fiber probe structure 110 can be embodied and implemented as a flexible tapered fiber probe structure as described in examples herein. The tapered fiber probe structure 110 can include one or more optical waveguides 120 (or “optical waveguides 120”), one or more microfluidic channels 130 (or “microfluidic channels 130”), one or more electrodes 140 (or “electrodes 140”), or any combination thereof. Only a single optical waveguide 120, microfluidic channel 130, and electrode 140 are denoted in FIG.1 for clarity. The optical waveguides 120, the microfluidic channels 130, and the electrodes 140 can be formed in the tapered fiber probe structure 110 such that they are collocated around and extend along a longitudinal axis of the tapered fiber probe structure 110 from a first end (e.g., a first distal end) to a second end (e.g., a second distal end) of the tapered fiber probe structure 110. For instance, the optical waveguides 120, the microfluidic channels 130, and the electrodes 140 can be formed in the tapered fiber probe structure 110 such that they are positioned at the same radial distance or different radial distances from a longitudinal axis (e.g., a center) of the tapered fiber probe structure 110. [0041] The first end of the tapered fiber probe structure 110 can be embodied as a micro-scale region having a diameter ranging between, for instance, approximately 50 micrometers (μm) to approximately 300 μm. In one embodiment, the first end of the tapered fiber probe structure 110 can have a diameter of approximately 150 μm. The first end of the tapered fiber probe structure 110 can include or be embodied as a micro-scale tip region where at least one of the optical waveguides 120, the microfluidic channels 130, or the electrodes 140 has one or more exposed portions or surfaces with micro-scale dimensions. The second end of the tapered fiber probe structure 110 can be Attorney Docket: 222204-2920 embodied as a macro-scale region having a diameter ranging between, for instance, approximately 1.5 millimeters (mm) to approximately 2.50 mm or larger in some cases. In one embodiment, the second end of the tapered fiber probe structure 110 can have a diameter of approximately 2 mm. The second end of the tapered fiber probe structure 110 can include or be embodied as a macro-scale connector region where at least one of the optical waveguides 120, the microfluidic channels 130, or the electrodes 140 has one or more exposed portions or surfaces with a macro-scale dimension or cross-sectional area that is approximately 10 to 30 times (e.g., 20 times) larger compared to a corresponding dimension or cross-sectional area of the component(s) at the first end of the tapered fiber probe structure 110. [0042] In the example shown, the tapered fiber probe structure 110 is embodied with a cylindrical shape and circular cross-section. In various embodiments, a cross-section of the first end of the tapered fiber probe structure 110 and a corresponding cross-section of the second end of the tapered fiber probe structure 110 are each embodied as a circular-shaped cross-section. For instance, a cross-section taken at or proximate to the first end of the tapered fiber probe structure 110 that is normal to the longitudinal axis of the tapered fiber probe structure 110 and a corresponding cross- section taken at or proximate to the second end of the tapered fiber probe structure 110 that is also normal to the longitudinal axis of the tapered fiber probe structure 110 are both circular-shaped cross- sections in the example shown. [0043] Although the tapered fiber probe structure 110 illustrated in FIG. 1 is embodied with a cylindrical shape and circular cross-section, the scope of the present disclosure is not so limited. In other examples the tapered fiber probe structure 110 may be embodied such that it has a rectangular- shaped cross-section, an annular-shaped cross-section, a triangular-shaped cross-section, a square- shaped cross-section, or a cross-section having another geometry. In some embodiments, a cross- section of the first end of the tapered fiber probe structure 110 and a corresponding cross-section of the second end of the tapered fiber probe structure 110 are each embodied as a rectangular-shaped cross-section, an annular-shaped cross-section, a triangular-shaped cross-section, a square-shaped cross-section, or a cross-section having another geometry. [0044] The tapered fiber probe structure 110 can be formed using and can thus include one or more preform materials used to fabricate fiber probe structures such as, for instance, at least one of a polymer material or a polycarbonate (PC) material. In some examples, the tapered fiber probe structure 110 can be formed using a polymer or polycarbonate rod having grooves or channels in which optical waveguides and electrodes can be inserted, and in which microfluidic channels can be formed as described in examples herein. In some cases, one or more polymer or polycarbonate films Attorney Docket: 222204-2920 can be wrapped around such a polymer or polycarbonate rod, as well as the optical waveguides, microfluidic channels, and electrodes positioned in the rod to form a preform of the tapered fiber probe structure 110. Such a preform can then be processed into a mini-preform that can be used to create the tapered fiber probe structure 110 as described further in examples herein. [0045] The optical waveguides 120 can be independently or collectively configured and operable to control optogenetics. In some examples, any or all of the optical waveguides 120 can be embodied as or include a polymer material. In other examples, any or all of the optical waveguides 120 can be embodied as or include a polycarbonate material. In some cases, any or all of the optical waveguides 120 can include a polycarbonate (PC) core and a poly(methyl 2-methylpropenoate) cladding. In one example, any or all of the optical waveguides 120 can include a PC core having a refractive index of n = 1.586 and a poly(methyl 2-methylpropenoate) cladding having a refractive index of n = 1.49. Any or all of the optical waveguides 120 can have a diameter ranging between, for instance, approximately 5 μm to approximately 300 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, each of the optical waveguides 120 of the probe device 100 can have a diameter of approximately 10 μm. [0046] The microfluidic channels 130 can be independently or collectively configured and operable to allow for focal drug infusion. In some cases, any or all of the microfluidic channels 130 can be formed as or from one of the aforementioned grooves or channels in a polymer or polycarbonate rod. The polymer or polycarbonate rod can then be used to fabricate a preform of the tapered fiber probe structure 110, then a mini-preform of the tapered fiber probe structure 110, and ultimately the tapered fiber probe structure 110. In other examples, any or all of the microfluidic channels 130 can be formed as or from a tube inserted in one of such aforementioned grooves or channels in such a polymer or polycarbonate rod. The polymer or polycarbonate rod can then be used to fabricate a preform, a mini-preform, and ultimately the tapered fiber probe structure 110 as described herein. For instance, any or all of the microfluidic channels 130 can be formed as or from a polycarbonate tube. Any or all of the microfluidic channels 130 can have a diameter ranging between, for instance, approximately 5 μm to approximately 100 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, each of the microfluidic channels 130 of the probe device 100 can have a diameter of approximately 25 μm. [0047] The electrodes 140 can be independently or collectively configured and operable to record extracellular voltage. In some cases, any or all of the electrodes 140 can be formed using a bismuth tin (BiSn) alloy material, a nichrome (NiCr) alloy material, a stainless steel alloy material, a gold or gold alloy material, a platinum or platinum alloy material, a tungsten or tungsten alloy Attorney Docket: 222204-2920 material, another material or alloy, or any combination thereof. In some examples, each of the electrodes 140 is formed using the same material or materials. In other examples, at least one of the electrodes 140 may be formed using a material that is different from any material used to form at least one of the other electrodes 140. Any or all of the electrodes 140 can have a diameter ranging between, for instance, approximately 5 μm to approximately 100 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, each of the electrodes 140 of the probe device 100 can have a diameter of approximately 25 μm. [0048] The probe device 100 also includes a tip region 150 positioned at the first end (e.g., first distal end) of the tapered fiber probe structure 110. The tip region 150 can include or be embodied as a micro-scale tip region where at least one of the optical waveguides 120, the microfluidic channels 130, or the electrodes 140 has one or more exposed portions or surfaces with micro-scale dimensions. The tip region 150 can include a tip that can be formed to various geometries (e.g., shapes or surface shapes), configurations (e.g., arrangements of probe components exposed at a surface of the tip), orientations (e.g., cut angles), and micro-scale dimensions (e.g., micro-scaled cross-sections of probe components exposed at a surface of the tip) as described in examples herein. As referenced herein, “probe components” can include, for instance, at least one of an optical waveguide, a microfluidic channel, an electrode, a tetrode, or another neural probe component. In the example shown, the tip of the tip region 150 is embodied as an angled tip 155. Either or both of the tip region 150 and the angled tip 155 can be defined by and formed as a result of a crosscut of at least one of the tapered fiber probe structure 110, the optical waveguides 120, the microfluidic channels 130, or the electrodes 140. For instance, the crosscut can be an angled crosscut that can be formed at a defined angle (^) relative to a cross-section of the tip region 150 or the longitudinal axis of the tapered fiber probe structure 110. In the example shown, the angled tip 155 can be formed at such a defined angle (^) relative to a cross-section of the tip region 150 or the longitudinal axis of the tapered fiber probe structure 110. [0049] In some examples, the tip of the tip region 150 may be embodied as a flat tip rather than an angled tip. In these examples, either or both of the tip region 150 and the tip of the tip region 150 can be defined by and formed as a result of a straight crosscut of at least one of the tapered fiber probe structure 110, the optical waveguides 120, the microfluidic channels 130, or the electrodes 140. For instance, the tip region 150 can be crosscut at an angle that is normal to the longitudinal axis of the tapered fiber probe structure 110. In some cases, the tip of the tip region 150 may be embodied as a multi-angled tip having multiple outer (e.g., exposed) surfaces that have been crosscut at different cut angles relative to a cross-section of the tip region 150 or the longitudinal axis of the tapered fiber Attorney Docket: 222204-2920 probe structure 110. In these examples, one or more exposed surfaces of any or all of the tapered fiber probe structure 110, the optical waveguides 120, the microfluidic channels 130, or the electrodes 140 may be formed to at least one of such different cut angles at the tip of the tip region 150. [0050] The tip region 150, the angled tip 155, or both can be formed to various defined dimensions such as, for instance, a defined diameter. In one example, the tip region 150, the angled tip 155, or both can be formed to a diameter of approximately 50 μm. In another example, the tip region 150, the angled tip 155, or both can be formed to a diameter ranging between 50 μm to 150 μm. In another example, the tip region 150, the angled tip 155, or both can be formed to a diameter of approximately 150 μm. In some cases, the tip region 150, the angled tip 155, or both can be formed to a diameter that is less than 50 μm or greater than 150 μm. Other dimensions can be relied upon. [0051] The probe device 100 further includes a backend connector region 160 positioned at or proximate to the second end (e.g., second distal end) of the tapered fiber probe structure 110. The backend connector region 160 can include or be embodied as a macro-scale connector region where at least one of the optical waveguides 120, the microfluidic channels 130, or the electrodes 140 has one or more exposed portions or surfaces with a macro-scale dimension or cross-sectional area that is approximately 10 to 30 times (e.g., 20 times) larger compared to a corresponding dimension or cross-sectional area of the component(s) at the tip region 150. The backend connector region 160 can be configured and operable to provide for coupling of one or more probe components of the tapered fiber probe structure 110 to one or more devices that are external to and separate from the probe device 100. In the example shown, the backend connector region 160 can be configured and operable to provide for coupling of one or more of the optical waveguides 120, the microfluidic channels 130, and the electrodes 140 to one or more devices that are external to and separate from the probe device 100. [0052] The backend connector region 160 can include one or more optic fibers 125 (or “optic fibers 125”). In the example shown, the backend connector region 160 includes multiple optic fibers 125 respectively coupled (e.g., optically, communicatively, operatively) to the optical waveguides 120 at or proximate to the second end of the tapered fiber probe structure 110. In various examples, each of the optic fibers 125 can be coupled to a backend portion (e.g., an exposed backend portion) of an optical waveguide 120 at or proximate to the second end of the tapered fiber probe structure 110 such that a tip portion of the optical waveguide 120 at the first end of the tapered fiber probe structure 110 can be coupled (e.g., optically, communicatively, operatively) to an external device. For instance, each of the optic fibers 125 can be coupled to the backend portion of an optical waveguide 120 at or proximate to the second end of the tapered fiber probe structure 110 such that Attorney Docket: 222204-2920 an exposed crosscut surface of the optical waveguide 120 at the angled tip 155 can be coupled (e.g., optically, communicatively, operatively) to an external device. Each of the optic fibers 125 in the example shown is directly coupled to one of the optical waveguides 120 at or proximate to the second end of the tapered fiber probe structure 110. [0053] In some examples, any or all of the optic fibers 125 can be embodied as or include a polymer material. In other examples, any or all of the optic fibers 125 can be embodied as or include a polycarbonate material. In some cases, any or all of the optic fibers 125 can be embodied as an optical fiber or cable. In one example, any or all of the optic fibers 125 can be embodied as a polymer optical waveguide (e.g., a PC core with a poly(methyl 2-methylpropenoate) cladding). In another example, any or all of the optic fibers 125 can be embodied as a polymer optical waveguide (e.g., a PC core with a poly(methyl 2-methylpropenoate) cladding) having a diameter of 200 μm. In other examples, the backend connector region 160 can further include one or more fiber optic connectors. In one example, any or all of the fiber optic connectors can be embodied as a stainless steel fiber optic ferrule. For instance, any or all of the fiber optic connectors can be embodied as a stainless steel fiber optic ferrule having an outer diameter of 1.25 mm. In one example, each of the fiber optic connectors can be coupled to one of the optic fibers 125. [0054] The backend connector region 160 can further include one or more microfluidic tubes 135 (or “microfluidic tubes 135”). In the example shown, the backend connector region 160 includes multiple microfluidic tubes 135 respectively coupled (e.g., fluidly, operatively) to the microfluidic channels 130 at or proximate to the second end of the tapered fiber probe structure 110. In various examples, each of the microfluidic tubes 135 can be coupled to a backend portion of a microfluidic channel 130 at or proximate to the second end of the tapered fiber probe structure 110 such that a tip portion of the microfluidic channel 130 at the first end of the tapered fiber probe structure 110 can be coupled (e.g., fluidly, operatively) to an external device. For instance, each of the microfluidic tubes 135 can be coupled to the backend portion of a microfluidic channel 130 at or proximate to the second end of the tapered fiber probe structure 110 such that an opened crosscut portion of the microfluidic channel 130 at the angled tip 155 can be coupled (e.g., fluidly, operatively) to an external device. [0055] Each of the microfluidic tubes 135 in the example shown is at least partly inserted into a microfluidic channel 130 at the second end of the tapered fiber probe structure 110. In one example, any or all of the microfluidic tubes 135 can be embodied as a polycarbonate (PC) tube. For instance, any or all of the microfluidic tubes 135 can be embodied as a PC tube having a 150 μm outer diameter (OD) and a 75 μm inner diameter (ID), although other OD and/or ID dimensions may be relied on in Attorney Docket: 222204-2920 some cases. In other examples, the backend connector region 160 can further include one or more fluidic connectors. In one example, each of the fluidic connectors can be coupled to one of the microfluidic tubes 135. [0056] The backend connector region 160 can further include one or more connector electrodes 145 (or “connector electrodes 145”). In the example shown, the backend connector region 160 includes multiple connector electrodes 145 respectively coupled (e.g., electrically, communicatively, operatively) to the electrodes 140 at or proximate to the second end of the tapered fiber probe structure 110. Each of the connector electrodes 145 can be coupled to a backend portion (e.g., an exposed backend portion) of an electrode 140 at or proximate to the second end of the tapered fiber probe structure 110 such that a tip portion of the electrode 140 at the first end of the tapered fiber probe structure 110 can be coupled (e.g., electrically, communicatively, operatively) to an external device. For instance, each of the connector electrodes 145 can be coupled to the backend portion of an electrode 140 at or proximate to the second end of the tapered fiber probe structure 110 such that an exposed crosscut surface of the electrode 140 at the angled tip 155 can be coupled (e.g., electrically, communicatively, operatively) to an external device. Each of the connector electrodes 145 in the example shown is directly coupled to one of the electrodes 140 at or proximate to the second end of the tapered fiber probe structure 110. [0057] Any or all of the connector electrodes 145 can be embodied as a wire such as, for example, a copper wire. In one example, any or all of the connector electrodes 145 can be embodied as an insulated copper wire. In one example, any or all of the connector electrodes 145 can be embodied as a 42 American Wire Gauge (AWG) copper wire, and other gauges can be relied upon. In other examples, the backend connector region 160 can further include one or more pin connectors, a printed circuit board (PCB), or any combination thereof. In one example, one end of each of the connector electrodes 145 can be coupled to the backend portion of an electrode 140 at or proximate to the second end of the tapered fiber probe structure 110 and another end of the connector electrode 145 can be coupled to a pin connector. In another example, one end of each of the connector electrodes 145 can be coupled to the backend portion of an electrode 140 at or proximate to the second end of the tapered fiber probe structure 110 and another end of the connector electrode 145 can be coupled to a PCB. [0058] The probe device 100 can further include a sealant to seal the microfluidic tubes 135 to the microfluidic channels 130 in some cases. For example, the probe device 100 can include an ultraviolet (UV) epoxy resin that can be coupled to the second end of the tapered fiber probe structure 110 and further coupled to the microfluidic tubes 135 and/or the aforementioned fluidic connectors. Attorney Docket: 222204-2920 The UV epoxy resin can be further coupled to any or all of the optical waveguides 120, the aforementioned fiber optic connectors, the optic fibers 125, the electrodes 140, the connector electrodes 145, the aforementioned pin connector or PCB, or any combination thereof, to provide support for such components. [0059] The probe device 100 can be fabricated according to various dimensions, geometries, configurations, or any combination thereof. In some cases, the probe device 100 can be fabricated such that the optical waveguides 120, the microfluidic channels 130, and/or the electrodes 140 are collocated within the tapered fiber probe structure 110 according to different arrangements. For example, the probe device 100 can be fabricated such that the optical waveguides 120, the microfluidic channels 130, and/or the electrodes 140 are collocated within the tapered fiber probe structure 110 according to any of the probe component arrangements 200a, 200b, or 200c described herein and illustrated in FIGS. 2A, 2B, and 2C, respectively, or according to another probe component arrangement. [0060] FIGS. 2A, 2B, and 2C illustrate example probe component arrangements of a multi- modal fiber probe device according to various aspects and embodiments of the present disclosure. FIGS.2A, 2B, and 2C illustrate different example probe component arrangements that can be formed in a multi-modal fiber probe device of the present disclosure such as, for instance, the probe device 100 described herein with reference to FIG. 1. FIG. 2A illustrates a cross-sectional view of an example tapered fiber probe structure 110 with a probe component arrangement 200a. More particularly, FIG.2A illustrates a cross-sectional view at the tip region 150 and/or the angled tip 155 of an example tapered fiber probe structure 110 with the probe component arrangement 200a. [0061] In the example shown, the tapered fiber probe structure 110 includes one of the optical waveguides 120, one of the microfluidic channels 130, and eight of the electrodes 140 collocated within the tapered fiber probe structure 110 according to the probe component arrangement 200a illustrated in FIG. 2A. Only a single electrode 140 is denoted in FIG. 2A for clarity. The optical waveguide 120 and the microfluidic channel 130 are coaxially located in the tapered fiber probe structure 110 in the probe component arrangement 200a shown in FIG. 2A. The optical waveguide 120 surrounds the microfluidic channel 130 from the first end to the second end of the tapered fiber probe structure 110 along a longitudinal axis of the tapered fiber probe structure 110. The longitudinal axis of the tapered fiber probe structure 110 in this example is located at a center of the microfluidic channel 130 and it extends into and out of the page of FIG.2A in a direction that is parallel to an axis Attorney Docket: 222204-2920 [0062] In the probe component arrangement 200a shown in FIG. 2A, the tapered fiber probe structure 110 includes an annular region 210 having an annular-shaped cross-section. The annular region 210 in this example surrounds the optical waveguide 120 and extends from the first end to the second end of the tapered fiber probe structure 110. The annular region 210 surrounds the optical waveguide 120 and extends into and out of the page of FIG.2A from the first end to the second end of the tapered fiber probe structure 110 in a direction that is parallel to the “Z” axis. In the probe component arrangement 200a shown in FIG. 2A, each of the electrodes 140 is positioned in and extends through the annular region 210 from the first end to the second end of the tapered fiber probe structure 110. For instance, each of the electrodes 140 is positioned in the annular region 210 and extends into and out of the page of FIG.2A from the first end to the second end of the tapered fiber probe structure 110 in a direction that is parallel to the “Z” axis. [0063] Any fiber probe structure described herein can include one or more divider regions positioned between various probe components (e.g., optical waveguide, electrode, microfluidic channel) integrated in and extending through the fiber probe structure. The divider regions can extend along an entire length of the fiber probe structure, and they can isolate (e.g., physically) and insulate (e.g., electrically, optically, electromagnetically, chemically) the probe components from one another. For example, the tapered fiber probe structure 110 can further include one or more divider regions positioned between at least two of the optical waveguides 120, the microfluidic channels 130, or the electrodes 140. Only a single divider region of the tapered fiber probe structure 110 is described herein for brevity and denoted in FIG.2A for clarity. [0064] The tapered fiber probe structure 110 includes a divider region 215 positioned in the annular region 210 between the optical waveguide 120 and each of the electrodes 140 in the example shown. The divider region 215 surrounds the optical waveguide 120 and extends from the first end to the second end of the tapered fiber probe structure 110. The divider region 215 surrounds the optical waveguide 120 and extends into and out of the page of FIG. 2A from the first end to the second end of the tapered fiber probe structure 110 in a direction that is parallel to the “Z” axis. The divider region 215 insulates and isolates the optical waveguide 120 from the electrodes 140 and vice versa. The divider region 215 includes material from one or more portions of at least one of the tapered fiber probe structure 110 (e.g., polymer or polycarbonate used to form the tapered fiber probe structure 110), the optical waveguide 120 (e.g., a poly(methyl 2-methylpropenoate) cladding of the optical waveguide 120), or the electrodes 140 (e.g., an insulating coating, wrap, sheath, or jacket of any or all of the electrodes 140). The tapered fiber probe structure 110 in this example further includes additional divider regions positioned in the annular region 210 between pairs of the electrodes 140. Attorney Docket: 222204-2920 These additional divider regions isolate (e.g., physically) and insulate (e.g., electrically, electromagnetically) the electrodes 140 from one another, and they include material from one or more portions of at least one of the tapered fiber probe structure 110 (e.g., polymer or polycarbonate used to form the tapered fiber probe structure 110) or the electrodes 140 (e.g., an insulating coating, wrap, sheath, or jacket of any or all of the electrodes 140). [0065] FIG. 2B illustrates another example probe component arrangement 200b according to various aspects and embodiments of the present disclosure. For instance, FIG.2B illustrates a cross- sectional view of another example tapered fiber probe structure 110 with the probe component arrangement 200b. More particularly, FIG.2B illustrates a cross-sectional view at the tip region 150 and/or the angled tip 155 of another example tapered fiber probe structure 110 with the probe component arrangement 200b. [0066] The tapered fiber probe structure 110 includes four of the optical waveguides 120, eight of the microfluidic channels 130, and eight of the electrodes 140 collocated within the tapered fiber probe structure 110 according to the probe component arrangement 200b illustrated in FIG.2B. Only a single optical waveguide 120, a single microfluidic channel 130, and a single electrode 140 are denoted in FIG. 2B for clarity. The optical waveguides 120 and the electrodes 140 are positioned at and arranged around a periphery region of the tapered fiber probe structure 110 in the probe component arrangement 200b shown in FIG.2B and the microfluidic channels 130 are positioned at a center region of the tapered fiber probe structure 110. In this example, each of the optical waveguides 120, the microfluidic channels 130, and the electrodes 140 extend from the first end to the second end of the tapered fiber probe structure 110 along a longitudinal axis of the tapered fiber probe structure 110. The longitudinal axis of the tapered fiber probe structure 110 in this example is located at a center of the tapered fiber probe structure 110 and it extends into and out of the page of FIG.2B in a direction that is parallel to an axis “Z.” [0067] The tapered fiber probe structure 110 can further include one or more divider regions positioned between at least two of any of the optical waveguides 120, the microfluidic channels 130, or the electrodes 140. In the example shown, the tapered fiber probe structure 110 includes divider regions 215 positioned between pairs of any of the optical waveguides 120, the microfluidic channels 130, and the electrodes 140. Only a single divider region 215 is denoted in FIG. 2B for clarity. The divider regions 215 in this example are located between such probe components and they extend from the first end to the second end of the tapered fiber probe structure 110. For instance, the divider regions 215 extend into and out of the page of FIG. 2B from the first end to the second end of the tapered fiber probe structure 110 in a direction that is parallel to the “Z” axis. The divider regions Attorney Docket: 222204-2920 215 isolate (e.g., physically) and insulate (e.g., electrically, optically, electromagnetically, chemically) the optical waveguides 120, the microfluidic channels 130, and the electrodes 140 from one another. The divider regions 215 include material from one or more portions of at least one of the tapered fiber probe structure 110 (e.g., polymer or polycarbonate used to form the tapered fiber probe structure 110), the optical waveguides 120 (e.g., a poly(methyl 2-methylpropenoate) cladding of the optical waveguides 120), the microfluidic channels 130 (e.g., polymer or polycarbonate tubes used to at least partly form the microfluidic channels 130), or the electrodes 140 (e.g., an insulating coating, wrap, sheath, or jacket of any or all of the electrodes 140). [0068] FIG. 2C illustrates another example probe component arrangement 200c according to various aspects and embodiments of the present disclosure. For instance, FIG.2C illustrates a cross- sectional view of another example tapered fiber probe structure 110 with the probe component arrangement 200c. More particularly, FIG.2C illustrates a cross-sectional view at the tip region 150 and/or the angled tip 155 of another example tapered fiber probe structure 110 with the probe component arrangement 200c. [0069] In the example shown, the tapered fiber probe structure 110 includes eight of the optical waveguides 120 and twelve of the microfluidic channels 130 collocated within the tapered fiber probe structure 110 according to the probe component arrangement 200c illustrated in FIG. 2C. In this example, the electrodes 140 are omitted from the tapered fiber probe structure 110. Only a single optical waveguide 120 and a single microfluidic channel 130 are denoted in FIG.2C for clarity. The optical waveguides 120 are positioned at and arranged around a periphery region of the tapered fiber probe structure 110 in the probe component arrangement 200c shown in FIG.2C and the microfluidic channels 130 are positioned at a center region of the tapered fiber probe structure 110. Each of the optical waveguides 120 and the microfluidic channels 130 extend from the first end to the second end of the tapered fiber probe structure 110 along a longitudinal axis of the tapered fiber probe structure 110. The longitudinal axis of the tapered fiber probe structure 110 in this example is located at a center of the tapered fiber probe structure 110 and it extends into and out of the page of FIG.2C in a direction that is parallel to an axis “Z.” [0070] The tapered fiber probe structure 110 can further include one or more divider regions positioned between at least two of any of the optical waveguides 120 and the microfluidic channels 130. The tapered fiber probe structure 110 includes divider regions 215 positioned between pairs of any of the optical waveguides 120 and the microfluidic channels 130. Only a single divider region 215 is denoted in FIG. 2C for clarity. The divider regions 215 in this example are located between such probe components and they extend from the first end to the second end of the tapered fiber probe Attorney Docket: 222204-2920 structure 110. For instance, the divider regions 215 extend into and out of the page of FIG. 2C from the first end to the second end of the tapered fiber probe structure 110 in a direction that is parallel to the “Z” axis. The divider regions 215 isolate (e.g., physically) and insulate (e.g., optically, electromagnetically, chemically) the optical waveguides 120 from the microfluidic channels 130 and vice versa. The divider regions 215 include material from one or more portions of at least one of the tapered fiber probe structure 110 (e.g., polymer or polycarbonate used to form the tapered fiber probe structure 110), the optical waveguides 120 (e.g., a poly(methyl 2-methylpropenoate) cladding of the optical waveguides 120), or the microfluidic channels 130 (e.g., polymer or polycarbonate tubes used to form the microfluidic channels 130). [0071] FIGS. 3A, 3B, and 3C illustrate example optical waveguide addressability modes of a multi-modal fiber probe device according to various aspects and embodiments of the present disclosure. For instance, FIGS. 3A, 3B, and 3C illustrate example optical waveguide addressability modes that can be implemented using a multi-modal fiber probe device of the present disclosure such as, for instance, the probe device 100 described herein with reference to FIG.1. [0072] FIGS. 3A, 3B, and 3C illustrate example optical waveguide addressability modes 300a, 300b, 300c, respectively, according to various aspects and embodiments of the present disclosure. For instance, FIGS.3A, 3B, and 3C each illustrate a cross-sectional view at the tip region 150 and/or the angled tip 155 of an example tapered fiber probe structure 110 formed according to the probe component arrangement 200c described herein and illustrated in FIG. 2C. For example, FIGS. 3A, 3B, and 3C illustrate a cross-sectional view of the optical waveguide addressability modes 300a, 300b, 300c, respectively, that can be implemented at the tip region 150 and/or the angled tip 155 of an example tapered fiber probe structure 110 formed according to the probe component arrangement 200c. In the examples shown in FIGS. 3A, 3B, and 3C, the optical waveguides 120 depicted with hatching are used to transmit light at approximately 660 nanometers (nm) and the optical waveguides 120 depicted with solid fill are used to transmit light at approximately 520 nm in the optical waveguide addressability mode 300a. Only a single optical waveguide 120 used to transmit light at approximately 520 nm and a single optical waveguide 120 used to transmit light at approximately 660 nm are denoted in each of FIGS. 3A, 3B, and 3C for clarity. In various embodiments, each of the optical waveguides 120 and other optical waveguides described herein can transmit light throughout the visible wavelengths. As demonstrated by the example optical waveguide addressability modes 300a, 300b, 300c illustrated in FIGS.3A, 3B, and 3C, any or all of the optical waveguides 120 of the probe device 100 can be configured and operable such that they are individually and collectively addressable (e.g., operated, controlled). Attorney Docket: 222204-2920 [0073] The tapered fiber probe structure 110 of the probe device 100 can be fabricated according to any of the probe component arrangements 200a, 200b, or 200c or another probe component arrangement by implementing a preform fabrication process 400a, a thermal drawing process (TDP) 400b, and a thermal tapering process (TTP) 400c described herein and illustrated in FIGS. 4A, 4B, and 4C, respectively. The probe device 100 in its entirety can be fabricated by implementing the preform fabrication process 400a, the thermal drawing process 400b, the thermal tapering process 400c, and a backend connection process 400d described herein and illustrated in FIGS. 4A, 4B, 4C and 4D, respectively. [0074] FIGS. 4A, 4B, 4C, and 4D collectively illustrate an example fabrication process for fabricating various multi-modal fiber probe devices of the present disclosure. FIG.4A illustrates an example preform fabrication process 400a according to various aspects and embodiments of the present disclosure. The preform fabrication process 400a illustrated in FIG.4A, or a variation thereof, can be used to fabricate various preforms that can each then be used to fabricate a fiber probe structure of a multi-modal fiber probe device described herein. The preform fabrication process 400a, or a variation thereof, can be implemented to fabricate a preform that can then be used to fabricate a fiber probe structure of a multi-modal fiber probe device described herein according to various dimensions, geometries, configurations, or any combination thereof. For example, the preform fabrication process 400a, or a variation thereof, can be implemented to fabricate a preform that can then be used to fabricate the tapered fiber probe structure 110 of the probe device 100 of FIG. 1 such that one or more of the optical waveguides 120, the microfluidic channels 130, and/or the electrodes 140 are formed in the tapered fiber probe structure 110 according to any of the probe component arrangements 200a, 200b, 200c described herein and illustrated in FIGS. 2A, 2B, and 2C, respectively, or according to another probe component arrangement. [0075] FIG. 4A shows example fabrication steps of the preform fabrication process 400a that can be implemented as described herein to form various preforms such as, for instance, a preform 405 shown in this example. In some cases, the preform 405 can be used to form a mini-preform 409 that can then be used to form the tapered fiber probe structure 110 as described herein with reference to FIGS.4B and 4C. [0076] At 402a, the preform fabrication process 400a can include forming one or more channels 430 in and/or through preform material such as, for instance, a preform rod 401. In some examples, one or more of the channels 430 can be formed in and/or through the preform rod 401 to create any or all of the optical waveguides 120, the microfluidic channels 130, or the electrodes 140 of the tapered fiber probe structure 110 described herein with reference to FIG. 1. In one example, the Attorney Docket: 222204-2920 preform rod 401 can be embodied as a PC rod. In this example the PC rod can be machined at 402a of the preform fabrication process 400a to create one or more of the channels 430 that can used to form one or more of the optical waveguides 120, the microfluidic channels 130, or the electrodes 140 in the tapered fiber probe structure 110. The channels 430 can be formed to various cross-sectional geometries, configurations, and dimensions within and through the preform rod 401. For instance, any or all of the channels 430 can be formed to have a circular-shaped cross-section, rectangular- shaped cross-section, a circular-shaped cross-section, a triangular-shaped cross-section, another cross-section geometry, or any combination thereof. [0077] At 404a, the preform fabrication process 400a can include inserting or inlaying one or more probe components such as, for example, one or more optical waveguides or electrodes in one or more of the channels 430 of the preform rod 401. In the example shown, some of the channels 430 are formed through a center region of the preform rod 401 and some of the channels 430 are formed at or proximate to a periphery region or surface of the preform rod 401. The channels 430 formed through the center region of the preform rod 401 can be used at 404a of the preform fabrication process 400a to insert, for instance, one or more optical waveguides and/or electrodes that can be respectively formed into one or more of the optical waveguides 120 and/or the electrodes 140 as described herein. [0078] The channels 430 formed at or proximate to the periphery region or surface of the preform rod 401 are embodied as spaces or grooves in this example. Such spaces or grooves can also be used at 404a of the preform fabrication process 400a to insert or inlay, for instance, one or more optical waveguides and/or electrodes that can be respectively formed into one or more of the optical waveguides 120 and/or the electrodes 140 as described herein. In one example, one or more optical waveguides with a PC core (e.g., having a refractive index n =1.586) and a poly(methyl 2- methylpropenoate) (PMMA; having a refractive index n = 1.49) cladding and one or more bismuth tin (BiSn) alloy electrodes can be inserted into respective channels 430 of the preform rod 401 at 404a of the preform fabrication process 400a. [0079] At 406a, the preform fabrication process 400a can include applying or wrapping a preform film 403 around the preform rod 401 and consolidating the wrapped preform rod 401 in a vacuum furnace to create the preform 405. In some cases, the preform film 403 can be embodied as a PC film. By performing the thermal drawing process 400b described herein, a finalized preform 405 having a diameter of approximately 30 mm in one example can be heated and drawn down to a fiber (e.g., the mini-preform 409) having a diameter of approximately 2 mm as illustrated in FIG.4B. Attorney Docket: 222204-2920 [0080] For a preform described herein (e.g., the preform 405), consolidation can be performed in some examples by heating the aforementioned wrapped preform rod 401 under vacuum at, for instance, approximately 190 degrees Celsius (°C). In some examples, polymer materials (e.g., PC films, tubes, rods, preforms, and mini-preforms) used to fabricate a preform described herein can be baked under vacuum at, for instance, approximately 80°C to ensure they are moisture free. In various other examples, the preform fabrication process 400a can further include one or more additional steps of machining, inserting and/or inlaying, film wrapping, and/or consolidation. [0081] In one example, an example preform 405 for an example tapered fiber probe structure 110 (e.g., FIG.2A) having eight of the electrodes 140, one of the microfluidic channels 130, and one of the optical waveguides 120 can be fabricated by first rolling a polyvinylidene fluoride (PVDF) film or films onto a PC tube (e.g., a tube for the microfluidic channel 130) to form an initial preform. Then, one or more PC films can be rolled onto the initial preform and consolidated. Next, eight grooves (e.g., eight of the channels 430) can be machined into the consolidated initial preform. The grooves can then be inlayed with a BiSn alloy material to form the eight electrodes 140. An additional PC film or films can then be wrapped around the consolidated initial preform having the inlayed BiSn alloy material and consolidated to create a final preform that can be used for the thermal drawing process 400b described herein with reference to FIG.4B. [0082] In another example, an example preform 405 for an example tapered fiber probe structure 110 (e.g., FIG. 2B) having eight of the electrodes 140, eight of the microfluidic channels 130, and four of the optical waveguides 120 can be fabricated by first milling (e.g., using a computer numerical control (CNC) milling machine) four channels into a solid PC rod to form an initial preform. The initial preform can then be wrapped with a PC film or films and consolidated. Next, four additional channels can be machined into the consolidated initial perform, which can then be wrapped with an additional PC film or films and consolidated. Then, twelve additional channels can be machined into the twice consolidated initial preform. The grooves can then be inlayed with eight BiSn alloy strips and four polymer waveguides (e.g., PC core, poly(methyl 2-methylpropenoate) cladding) to respectively form the eight electrodes 140 and the four optical waveguides 120. Finally, the twice consolidated initial preform having the inlayed BiSn alloy material and polymer waveguides can be wrapped with an additional PC film or films and consolidated to create a final preform that can be used for the thermal drawing process 400b described herein with reference to FIG.4B. [0083] In another example, an example preform 405 for an example the tapered fiber probe structure 110 (e.g., FIG.2C) having twelve of the microfluidic channels 130 and eight of the optical waveguides 120 can be fabricated in a similar manner as described above for an example preform Attorney Docket: 222204-2920 405 for an example tapered fiber probe structure 110 having eight of the electrodes 140, eight of the microfluidic channels 130, and four of the optical waveguides 120. A few differences being, for instance: a) eight channels can be machined for the second layer of the microfluidic channels 130; b) there will be eight of the optical waveguides 120 instead of four; and c) the BiSn strips will be omitted from the outermost layer of the preform. [0084] FIG. 4B illustrates an example thermal drawing process 400b according to various aspects and embodiments of the present disclosure. The thermal drawing process 400b illustrated in FIG.4B, or a variation thereof, can be used to fabricate various mini-preforms that can each then be used to fabricate a fiber probe structure of a multi-modal fiber probe device described herein. The thermal drawing process 400b, or a variation thereof, can be implemented to fabricate a mini-preform that can then be used to fabricate a fiber probe structure of a multi-modal fiber probe device described herein according to various dimensions, geometries, configurations, or any combination thereof. For example, the thermal drawing process 400b, or a variation thereof, can be implemented to fabricate a mini-preform that can then be used to fabricate the tapered fiber probe structure 110 of the probe device 100 of FIG.1 such that one or more of the optical waveguides 120, the microfluidic channels 130, and/or the electrodes 140 are formed in the tapered fiber probe structure 110 according to any of the probe component arrangements 200a, 200b, 200c described herein and illustrated in FIGS.2A, 2B, and 2C, respectively, or according to another probe component arrangement. [0085] In various examples, the thermal drawing process 400b can be implemented to form a mini-preform from a preform that has been fabricated using the preform fabrication process 400a described herein and illustrated in FIG.4A. In these or other examples, the thermal drawing process 400b can be implemented to form the mini-preform such that the optical waveguides, microfluidic channels, and/or electrodes of the preform are formed in the mini-preform in the same or similar manner as they are formed in the preform. For instance, the thermal drawing process 400b can be implemented to form the mini-preform such that each of the optical waveguides, microfluidic channels, and electrodes is formed in the mini-preform with the same or similar cross-sectional geometry and relative position as in the preform. [0086] FIG.4B shows example fabrication steps of the thermal drawing process 400b that can be implemented as described herein to form various mini-preforms such as, for instance, a mini- preform 409 shown in this example. The mini-preform 409 in this example can be formed from the preform 405 described herein and illustrated in FIG.4A. Thermal drawing process 400b can be implemented to form the mini-preform 409 such that the optical waveguides 420, the channels 430, and the electrodes 440 are formed in the mini-preform 409 in the same or similar manner as they Attorney Docket: 222204-2920 are formed in the preform 405, for instance, with the same or similar cross-sectional geometry and relative position as in the preform 405. [0087] The thermal drawing process 400b can include heating and pulling a preform such as, for instance, the preform 405. For example, the preform 405 can be heated in a furnace and pulled into a fiber 407 (e.g., an optical fiber) using, for instance, a capstan motor. The furnace can be divided into a top section, a middle section, and a bottom section that can be individually set to different temperatures. The top section of the furnace can be where the preform 405 is preheated. The middle section of the furnace can be where the preform 405 is softened and pulled into the fiber 407. The bottom section of the furnace can be where the resulting fiber 407 is cooled. In one example, the top, middle, and bottom sections of the furnace can be set to 150°C, 275°C, and 120°C, respectively. In some examples the temperature of the preform 405 in any given section of the furnace during the thermal drawing process 400b is the same or approximately the same as the temperature of such a furnace section. In other examples the temperature of the preform 405 in any given section of the furnace during the thermal drawing process 400b is different from the temperature of such a furnace section. [0088] In some examples, the cross-sectional dimensions (e.g., diameter) of the fiber 407 being formed during the thermal drawing process 400b can be closely monitored using a laser micrometer. The cross-sectional dimensions (e.g., diameter) of the fiber 407 can also be controlled during the thermal drawing process 400b by adjusting the pulling speed of the capstan motor and/or the temperature of one or more sections of the furnace. In the example shown, the thermal drawing process 400b can further include cutting the fiber 407 to form one or more mini-preforms 409. The thermal drawing process 400b can include pulling the preform 405 having a diameter of approximately 30 mm into the fiber 407 such that the fiber 407 and the mini-preform 409 each have a diameter of approximately 2 mm. The fiber 407 can then be cut into, for example, one or more 10 centimeter (cm) long mini-preforms 409 that can each be used for the thermal tapering process 400c described herein with reference to FIG.4C. [0089] FIG. 4C illustrates an example thermal tapering process 400c according to various aspects and embodiments of the present disclosure. The thermal tapering process 400c may be implemented and referred to herein as a convergence tapering process. The thermal tapering process 400c illustrated in FIG. 4C, or a variation thereof, can be used to fabricate various fiber probe structures of different multi-modal fiber probe devices described herein. The thermal tapering process 400c, or a variation thereof, can be implemented to fabricate a fiber probe structure of a multi-modal fiber probe device described herein according to various dimensions, geometries, configurations, or Attorney Docket: 222204-2920 any combination thereof. For example, the thermal tapering process 400c, or a variation thereof, can be implemented to fabricate the tapered fiber probe structure 110 of the probe device 100 of FIG. 1 such that one or more of the optical waveguides 120, the microfluidic channels 130, and/or the electrodes 140 are formed in the tapered fiber probe structure 110 according to any of the probe component arrangements 200a, 200b, 200c described herein and illustrated in FIGS.2A, 2B, and 2C, respectively, or according to another probe component arrangement. [0090] In various examples, the thermal tapering process 400c can be implemented to form a fiber probe structure from a mini-preform that has been fabricated from a preform using the preform fabrication process 400a and the thermal drawing process 400b described herein and illustrated in FIGS.4A and 4B, respectively. In these or other examples, the thermal tapering process 400c can be implemented to form the fiber probe structure such that the optical waveguides, microfluidic channels, and/or electrodes of the preform and mini-preform are formed in the fiber probe structure in the same or similar manner as they are formed in the preform and the mini-preform. For instance, the thermal tapering process 400c can be implemented to form the fiber probe structure such that each of the optical waveguides, microfluidic channels, and electrodes is formed in the fiber probe structure with the same or similar cross-sectional geometry and relative position as in each of the preform and the mini-preform. For example, the thermal tapering process 400c can be implemented to form the fiber probe structure such that each of the optical waveguides, microfluidic channels, and electrodes is formed in a reduced cross-section region created in the mini-preform and/or at a tip region of the fiber probe structure with the same or similar cross-sectional geometry and relative position as in each of the preform and the mini-preform. [0091] FIG. 4C shows example fabrication steps of the thermal tapering process 400c that can be implemented as described herein to form various fiber probe structures such as, for instance, the tapered fiber probe structure 110 shown in this example. The tapered fiber probe structure 110 in this example can be formed from the mini-preform 409 described herein and illustrated in FIG.4B. The thermal tapering process 400c can be implemented to form the tapered fiber probe structure 110 such that the optical waveguides 120, the microfluidic channels 130, and the electrodes 140 are formed in the tapered fiber probe structure 110 in the same or similar manner as the optical waveguides 420, the channels 430, and the electrodes 440 are formed in the mini-preform 409, for instance, with the same or similar cross-sectional geometry and relative position as in the mini-preform 409. Implementation of the thermal tapering process 400c in this example results in the formation of the optical waveguides 120, the microfluidic channels 130, and the electrodes 140 from the optical waveguides 420, the channels 430, and the electrodes 440, respectively. In this example, the thermal Attorney Docket: 222204-2920 tapering process 400c can be implemented to form the tapered fiber probe structure 110 such that each of the optical waveguides 120, the microfluidic channels 130, and the electrodes 140 is formed in a reduced cross-section region 450 created in the mini-preform 409 and/or at the tip region 150 of the tapered fiber probe structure 110 with the same or similar cross-sectional geometry and relative position as in the mini-preform 409. [0092] Similar to a glass pipette pulling process, at 402c of the thermal tapering process 400c the mini-preform 409 can be heated until it is softened. The mini-preform 409 is then pulled in opposite directions to create the reduced cross-section region 450 in the mini-preform 409 as illustrated in FIG. 4C. At 402c, the thermal tapering process 400c can include holding the mini- preform 409 in place and/or adjusting the alignment of the mini-preform 409 using opto-mechanical components. The thermal tapering process 400c can further include heating and softening the mini- preform 409 using a furnace set to, for instance, approximately 230°C. In some examples the temperature of the mini-preform 409 in the furnace during the thermal tapering process 400c is the same or approximately the same as the temperature of the furnace. In other examples the temperature of the mini-preform 409 in the furnace during the thermal tapering process 400c is different from the temperature of the furnace. Once the mini-preform 409 is softened to a desired degree, it can be pulled in opposite directions, for example, by a computer controlled linear motor to transform the mini-preform 409 into a tapered mini-preform structure 410 having the reduced cross-section region 450. The speed and/or travel distance of the linear motor can be altered to adjust the resulting geometry or area (e.g., diameter) of the reduced cross-section region 450. The resulting geometry or area (e.g., diameter) of the reduced cross-section region 450 can be closely monitored during the thermal tapering process 400c by using a laser micrometer. The resulting geometry or area (e.g., diameter) of the reduced cross-section region 450 can also be controlled during the thermal tapering process 400c by adjusting the pulling speed of the linear motor and/or the temperature of the furnace. [0093] At 404c, the process includes cutting the reduced cross-section region 450 of the tapered mini-preform structure 410 at a desired angle (^) to produce two individual tapered fiber probe structures 110. For instance, after softening and pulling the mini-perform 409 at 402c, the resulting tapered mini-preform structure 410 can be cut at a desired location along the reduced cross-section region 450 to produce two individual tapered fiber probe structures 110. To produce the tapered fiber probe structure 110 such that it has a tip region 150 that minimally damages tissue when inserted into a subject (e.g., a patient, person, animal), the reduced cross-section region 450 can be cut with a crosscut 411 at a defined angle (^) to create the angled tip 155 of the tapered fiber probe structure 110. For example, the reduced cross-section region 450 can be crosscut at a defined angle (^) relative Attorney Docket: 222204-2920 to a longitudinal axis or a cross-section of at least one of the reduced cross-section region 450, the mini-preform 409, or the tapered mini-preform structure 410 at any location along the reduced cross- section region 450 to form the angled tip 155 of the tapered fiber probe structure 110. [0094] FIG. 4D illustrates an example backend connection process 400d according to various aspects and embodiments of the present disclosure. The backend connection process 400d illustrated in FIG. 4D, or a variation thereof, can be used to fabricate various multi-modal fiber probe devices described herein. For instance, the backend connection process 400d can be implemented to fabricate a backend connector region of a multi-modal fiber probe device described herein such as, for instance, the backend connector region 160 of the probe device 100. In some cases, the backend connection process 400d of FIG.4D can include the use of translation stages and a digital microscope to provide finer position control during connection. In one example, the backend connection process 400d can be implemented as described herein with reference to FIG.4D. [0095] At 402d, the backend connection process 400d can include coupling (e.g., electrically, operatively) the connector electrodes 145 to the electrodes 140 located at or proximate to the second end of the tapered fiber probe structure 110. For instance, the connector electrodes 145 can be coupled to the electrodes 440 formed in the tapered mini-preform structure 410 as described herein with reference to the preform fabrication process 400a, the thermal drawing process 400b, and the thermal tapering process 400c respectively illustrated in FIGS.4A, 4B, and 4C. The electrical connection of the connector electrodes 145 to the electrodes 140 can be achieved in one example by heating the second end of the tapered fiber probe structure 110 to approximately 160°C to melt portions of the electrodes 140 located in this region of the tapered fiber probe structure 110 to a desired melted state. This temperature (e.g., 160°C) is high enough to melt the electrodes 140 but low enough to avoid damaging the tapered fiber probe structure 110. In one example, each of the connector electrodes 145 can be embodied as a copper wire (e.g., an insulated copper wire) that can be inserted into one of the melted electrodes 140 located in the tapered fiber probe structure 110 at its second end. In some cases, the connector electrodes 145 (e.g., copper wires) can be guided by a hypodermic needle when lowered into the melted electrodes 140. The second end of the tapered fiber probe structure 110 can then be cooled to allow the electrodes 140 and the connector electrodes 145 to solidify. [0096] At 404d, the backend connection process 400d can include coupling (e.g., fluidly, communicatively, operatively) the microfluidic tubes 135 to the microfluidic channels 130 located at or proximate to the second end of the tapered fiber probe structure 110. For instance, the microfluidic tubes 135 can be coupled to the channels 430 formed in the tapered mini-preform structure 410 as described herein with reference to the preform fabrication process 400a, the thermal drawing process Attorney Docket: 222204-2920 400b, and the thermal tapering process 400c respectively illustrated in FIGS. 4A, 4B, and 4C. The microfluidic connection of the microfluidic tubes 135 to the microfluidic channels 130 can be achieved in one example by inserting a drawn microfluidic tube 135 embodied as a drawn polycarbonate (PC) tube into each of the microfluidic channels 130 located in the tapered fiber probe structure 110 at its second end. In one example, each of the microfluidic tubes 135 can be embodied as a PC tube having an OD of approximately 150 μm and an ID of approximately 75 μm, although other PC tubes having other ODs and/or IDs can used in some cases. [0097] At 406d, the backend connection process 400d can include coupling (e.g., optically, communicatively, operatively) the optic fibers 125 to the optical waveguides 120 located at or proximate to the second end of the tapered fiber probe structure 110. For instance, the optic fibers 125 can be coupled to the optical waveguides 420 formed in the tapered mini-preform structure 410 as described herein with reference to the preform fabrication process 400a, the thermal drawing process 400b, and the thermal tapering process 400c respectively illustrated in FIGS. 4A, 4B, and 4C. The optic connection of the optic fibers 125 to the optical waveguides 120 can be achieved in one example by coupling a drawn optic fiber 125 embodied as a drawn polymer optical fiber (e.g., a PC core with a poly(methyl 2-methylpropenoate) cladding) to one of the optical waveguides 120 located in the tapered fiber probe structure 110 at its second end. In one example, each of the optic fibers 125 can be embodied as a polymer optical fiber having a diameter of approximately 200 μm. In one example, each of the optic fibers 125 can be embodied as a polymer optical fiber that can be directly coupled at 406d of the backend connection process 400d to one of the optical waveguides 120 via an epoxy. In some cases, each of the optic fibers 125 can be embodied as a polymer optical fiber that can be polished using, for instance, 30-1 μm grit sandpaper prior to being coupled to a respective optical waveguide 120. [0098] In some cases, the backend connection process 400d can also include using a UV epoxy resin to seal and fix at least one of the aforementioned electrical, microfluidic, or optical connections in place. By completing the backend connection process 400d illustrated in FIG. 4D, a multi-modal fiber probe device described herein can be fitted with industry standard adapters compatible with electrophysiology equipment, optical modules, and drug delivery pumps. [0099] FIGS. 5A, 5B, and 5C illustrate various views of another example multi-modal fiber probe device 500 (or “probe device 500”) according to various aspects and embodiments of the present disclosure. FIG. 5A illustrates a perspective view of the example multi-modal fiber probe device 500 according to various aspects and embodiments of the present disclosure. FIG. 5B illustrates a top view of a tip region 550 of the example multi-modal fiber probe device 500 according Attorney Docket: 222204-2920 to various aspects and embodiments of the present disclosure. FIG. 5C illustrates an isometric view of the tip region 550 of the example multi-modal fiber probe device 500 according to various aspects and embodiments of the present disclosure. The probe device 500 can be designed, embodied, and implemented as a flexible, multi-modal neural fiber probe device in examples herein. For instance, the probe device 500 can be designed, embodied, and implemented as a Tapered Drug delivery, Optical stimulation, and Electrophysiology (T-DOpE) probe device described in various embodiments herein. Similar to the probe device 100, the probe device 500 offers relatively higher complexities at a tip region compared to existing devices while also easing the connection between a backend connector region and external electronics that may be coupled to the probe device 500. [0100] The probe device 500 is an example alternative embodiment of the probe device 100 described herein and illustrated in FIG. 1. The probe device 500 can include the same or similar structure, components, features, materials, and functionality as that of the probe device 100. A difference between the probe device 500 and the probe device 100 is that the cross-sectional geometry of the probe device 500 is rectangular, as opposed to circular. Another difference between the probe device 500 and the probe device 100 is the arrangement of optical waveguides, microfluidic channels, and electrodes relative to one another in each of such devices. Another difference between the probe device 500 and the probe device 100 is the number of optical waveguides, microfluidic channels, and electrodes in each of such devices. Another difference between the probe device 500 and the probe device 100 is the electrodes in the probe device 500 are bundled in subsets or groupings referred to as “tetrodes.” Another difference between the probe device 500 and the probe device 100 is the electrode material of the tetrodes in the probe device 100 may be a bismuth tin (BiSn) alloy in some examples while the electrode material of the tetrodes in the probe device 500 may be a nichrome (NiCr) alloy in some examples. [0101] The probe device 500 illustrated in FIGS. 5A to 5C includes a tapered fiber probe structure 510. The tapered fiber probe structure 510 can be embodied and implemented as a flexible tapered fiber probe structure as described in examples herein. The tapered fiber probe structure 510 can include one or more optical waveguides 520, one or more microfluidic channels 530, one or more tetrodes 540a, 540b, 540c (or “tetrodes 540”), or any combination thereof. In the example shown, the tapered fiber probe structure 510 includes a single optical waveguide 520 and a single microfluidic channel 530. In this example, each of the tetrodes 540 is embodied as and thus includes electrodes 542, 544, 546, 548. For instance, the tetrode 540a is embodied as and includes electrodes 542a, 544a, 546a, 548a, the tetrode 540b is embodied as and includes electrodes 542b, 544b, 546b, 548b, and the tetrode 540c is embodied as and includes electrodes 542c, 544c, 546c, 548c. Only a single electrode Attorney Docket: 222204-2920 542a, 542b, 542c is respectively denoted for the tetrodes 540a, 540b, 540c in FIG.5C for clarity. The optical waveguide 520, the microfluidic channel 530, and the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548) can be formed in the tapered fiber probe structure 510 such that they are collocated approximately parallel to and extend along a longitudinal axis of the tapered fiber probe structure 510 from a first end (e.g., a first distal end) to a second end (e.g., a second distal end) of the tapered fiber probe structure 510 as illustrated in FIGS. 5A, 5B, and 5C. For instance, centerlines of the optical waveguide 520, the microfluidic channel 530, and the tetrodes 540 can be parallel to and coplanar or approximately coplanar with one another along the longitudinal axis of the tapered fiber probe structure 510 from the first end to the second end of the tapered fiber probe structure 510. [0102] The first end of the tapered fiber probe structure 510 can be embodied as a micro-scale region having a first width (w1) ranging between, for instance, approximately 50 μm to approximately 750 μm. In one embodiment, the first end of the tapered fiber probe structure 510 can have a first width (w1) of approximately 300 μm. The first end of the tapered fiber probe structure 510 can have a first thickness (t1) ranging between, for instance, approximately 10 μm to approximately 250 μm. In one embodiment, the first end of the tapered fiber probe structure 510 can have a first thickness (t1) of approximately 100 μm. The first end of the tapered fiber probe structure 510 can include or be embodied as a micro-scale tip region where at least one of the optical waveguide 520, the microfluidic channel 530, or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of the tetrodes 540) has one or more exposed portions or surfaces with micro-scale dimensions. The second end of the tapered fiber probe structure 510 can be embodied as a macro-scale region having a second width (w₂) ranging between, for instance, approximately 1.5 mm to approximately 2.5 mm or larger in some cases. In one embodiment, the second end of the tapered fiber probe structure 510 can have a second width (w₂) of approximately 2 mm. The second end of the tapered fiber probe structure 510 can have a second thickness (t₂) ranging between, for instance, approximately 0.25 mm to approximately 1.25 mm. In one embodiment, the second end of the tapered fiber probe structure 510 can have a second thickness (t2) of approximately 0.75 mm. The second end of the tapered fiber probe structure 510 can include or be embodied as a macro-scale connector region where at least one of the optical waveguide 520, the microfluidic channel 530, or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of the tetrodes 540) has one or more exposed portions or surfaces with a macro-scale dimension or cross- sectional area that is approximately 10 to 30 times (e.g., 20 times) larger compared to a corresponding dimension or cross-sectional area of the component(s) at the first end of the tapered fiber probe structure 510. Attorney Docket: 222204-2920 [0103] In the example shown, the tapered fiber probe structure 510 is embodied with a rectangular shape and rectangular cross-section. In various embodiments, a cross-section of the first end of the tapered fiber probe structure 510 and a corresponding cross-section of the second end of the tapered fiber probe structure 510 are each embodied as a rectangular-shaped cross-section. For instance, a cross-section taken at or proximate to the first end of the tapered fiber probe structure 510 that is normal to the longitudinal axis of the tapered fiber probe structure 510 and a corresponding cross-section taken at or proximate to the second end of the tapered fiber probe structure 510 that is also normal to the longitudinal axis of the tapered fiber probe structure 510 are both rectangular- shaped cross-sections in the example shown. Although the tapered fiber probe structure 510 illustrated in FIGS.5A to 5C is embodied with a rectangular shape and rectangular cross-section, the scope of the present disclosure is not so limited. In other examples the tapered fiber probe structure 510 may be embodied such that it has a circular-shaped cross-section, an annular-shaped cross- section, a triangular-shaped cross-section, a square-shaped cross-section, or a cross-section having another geometry. In some embodiments, a cross-section of the first end of the tapered fiber probe structure 510 and a corresponding cross-section of the second end of the tapered fiber probe structure 510 are each embodied as a circular-shaped cross-section, an annular-shaped cross-section, a triangular-shaped cross-section, a square-shaped cross-section, or a cross-section having another geometry. [0104] The tapered fiber probe structure 510 can be formed using and can thus include one or more preform materials used to fabricate fiber probe structures such as, for instance, at least one of a polymer material or a polycarbonate (PC) material. In some examples, the tapered fiber probe structure 510 can be formed using one or more polymer or PC plates having grooves or channels in which optical waveguides and electrodes can be inserted, and in which microfluidic channels can be formed as described in examples herein. In some cases, the tapered fiber probe structure 510 can be formed from a rectangular PC preform that can be created by milling (e.g., using a CNC milling machine) or otherwise forming multiple grooves or channels in a PC plate. In one example, a first portion (e.g., half) of each of such grooves or channels may be milled into a first PC plate and a second portion (e.g., half) of each of such grooves or channels may be milled in a second PC plate such that the first and second portions of each of the grooves or channels are aligned when the first and second PC plates are positioned (e.g., stacked) on one another to form the rectangular PC preform. In another example, the tapered fiber probe structure 510 can be formed from a rectangular PC preform that can be created by milling or otherwise forming multiple grooves or channels in a PC plate and stacking one or more additional PC plates on at least one side or surface of the PC plate Attorney Docket: 222204-2920 (e.g., a top or bottom side or surface) to form the rectangular PC preform. Either or both of the aforementioned rectangular preforms can then be respectively processed into a mini-preform that can be used to create the tapered fiber probe structure 510 as described further in examples herein. [0105] The optical waveguide 520 can be configured and operable to control optogenetics. In some examples, the optical waveguide 520 can be embodied as or include a polymer material. In other examples, the optical waveguide 520 can be embodied as or include a polycarbonate material. In some cases, the optical waveguide 520 can include a polycarbonate (PC) core and a poly(methyl 2-methylpropenoate) cladding. In one example, the optical waveguide 520 can include a PC core having a refractive index of n = 1.586 and a poly(methyl 2-methylpropenoate) cladding having a refractive index of n = 1.49. The optical waveguide 520 can have a diameter ranging between, for instance, approximately 5 μm to approximately 300 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, the optical waveguide 520 of the probe device 500 can have a diameter of approximately 50 μm. [0106] The microfluidic channel 530 can be configured and operable to allow for focal drug infusion. In some cases, the microfluidic channel 530 can be formed as or from one of the grooves or channels that can be formed in the aforementioned rectangular PC preform, which can then be used to create a mini-preform of the tapered fiber probe structure 510 and ultimately the tapered fiber probe structure 510. In other examples, the microfluidic channel 530 can be formed as or from a tube inserted in one of the grooves or channels that can be formed in the above-described rectangular PC preform that can be used to create a mini-preform of the tapered fiber probe structure 510 and ultimately the tapered fiber probe structure 510 as described herein. For instance, the microfluidic channel 530 can be formed as or from a PC tube having a 150 μm OD and a 75 μm inner diameter ID, although other OD and/or ID dimensions may be relied on in some cases. The microfluidic channel 530 can have a diameter ranging between, for instance, approximately 5 μm to approximately 100 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, the microfluidic channel 530 of the probe device 500 can have a diameter of approximately 75 μm. [0107] The tetrodes 540 and the electrodes 542, 544, 546, 548 can be independently or collectively configured and operable to record extracellular voltage. In some cases, any or all of the electrodes 542, 544, 546, 548 can be formed using a bismuth tin (BiSn) alloy material, a nichrome (NiCr) alloy material, a stainless steel alloy material, a gold or gold alloy material, a platinum or platinum alloy material, a tungsten or tungsten alloy material, another material or alloy, or any combination thereof. In some examples, each of the electrodes 542, 544, 546, 548 of each of the Attorney Docket: 222204-2920 tetrodes 540 is formed using the same material or materials. In other examples, at least one of the electrodes 542, 544, 546, 548 of any of the tetrodes 540 may be formed using a material that is different from any material used to form at least one of the other electrodes 542, 544, 546, 548 in at least one of the other tetrodes 540. Any or all of the electrodes 542, 544, 546, 548 can have a diameter ranging between, for instance, approximately 5 μm to approximately 100 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, each of the electrodes 542, 544, 546, 548 of the probe device 500 can have a diameter of approximately 25 μm. [0108] The probe device 500 also includes a tip region 550 positioned at the first end (e.g., first distal end) of the tapered fiber probe structure 510. The tip region 550 can include or be embodied as a micro-scale tip region where at least one of the optical waveguide 520, the microfluidic channel 530, or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of the tetrodes 540) has one or more exposed portions or surfaces with micro-scale dimensions. The tip region 550 can include a tip that can be formed to various geometries (e.g., shapes or surface shapes), configurations (e.g., arrangements of probe components exposed at a surface of the tip), orientations (e.g., cut angles), and micro-scale dimensions (e.g., micro-scaled cross-sections of probe components exposed at a surface of the tip) as described in examples herein. In the example shown, the tip of the tip region 550 is embodied as an angled tip 555. Either or both of the tip region 550 and the angled tip 555 can be defined by and formed as a result of a crosscut of at least one of the tapered fiber probe structure 510, the optical waveguide 520, the microfluidic channel 530, the tetrodes 540, or the electrodes 542, 544, 546, 548. For instance, the crosscut can be an angled crosscut that can be formed at a defined angle (^) relative to a cross-section of the tip region 550 or the longitudinal axis of the tapered fiber probe structure 510. In the example shown, the angled tip 555 can be formed at such a defined angle (^) relative to a cross-section of the tip region 550 or the longitudinal axis of the tapered fiber probe structure 510. [0109] In some examples, the tip of the tip region 550 may be embodied as a flat tip rather than an angled tip. In these examples, either or both of the tip region 550 and the tip of the tip region 550 can be defined by and formed as a result of a straight crosscut of at least one of the tapered fiber probe structure 510, the optical waveguide 520, the microfluidic channel 530, or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c). For instance, the tip region 550 can be crosscut at an angle that is normal to the longitudinal axis of the tapered fiber probe structure 510. In some cases, the tip of the tip region 550 may be embodied as a multi-angled tip having multiple outer (e.g., exposed) surfaces that have been crosscut at different cut angles relative to a cross-section of the tip region 550 or the longitudinal axis of the tapered fiber probe Attorney Docket: 222204-2920 structure 510. In these examples, one or more exposed surfaces of any or all of the tapered fiber probe structure 510, the optical waveguide 520, the microfluidic channel 530, or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) may be formed to at least one of such different cut angles at the tip of the tip region 550. The tip region 550, the angled tip 555, or both can be formed to various defined dimensions such as, for instance, at least one of a defined width or a defined thickness. The tip region 550, the angled tip 555, or both can be formed to the first width (w₁) ranging between, for instance, approximately 50 μm to approximately 750 μm. In one embodiment, the tip region 550, the angled tip 555, or both can have a width of approximately 500 μm. The tip region 550, the angled tip 555, or both can be formed to the first thickness (t₁) ranging between, for instance, approximately 10 μm to approximately 250 μm. In one embodiment, the tip region 550, the angled tip 555, or both can have a thickness of approximately 100 μm. [0110] The probe device 500 further includes a backend connector region 560 positioned at or proximate to the second end (e.g., second distal end) of the tapered fiber probe structure 510. The backend connector region 560 can include or be embodied as a macro-scale connector region where at least one of the optical waveguide 520, the microfluidic channel 530, or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of the tetrodes 540) has one or more exposed portions or surfaces with a macro-scale dimension or cross-sectional area that is approximately 10 to 30 times (e.g., 20 times) larger compared to a corresponding dimension or cross-sectional area of the component(s) at the tip region 550. The backend connector region 560 can be configured and operable to provide for coupling of one or more probe components of the tapered fiber probe structure 510 to one or more devices that are external to and separate from the probe device 500. In the example shown, the backend connector region 560 can be configured and operable to provide for coupling of the optical waveguide 520, the microfluidic channel 530, and the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540) to one or more devices that are external to and separate from the probe device 500. [0111] The backend connector region 560 includes a backend portion (e.g., an exposed backend portion) of the optical waveguide 520 extending from the second end of the tapered fiber probe structure 510. The backend portion of the optical waveguide 520 can be configured and operable for coupling (e.g., optically, communicatively, operatively) to an external optical component or device such that a tip portion of the optical waveguide 520 at the first end of the tapered fiber probe structure 510 can be coupled (e.g., optically, communicatively, operatively) to such an external optical component or device. For instance, the backend portion of the optical waveguide 520 can be configured (e.g., formed) and operable for coupling to an external optical component or device such Attorney Docket: 222204-2920 that an exposed crosscut surface of the optical waveguide 520 at the angled tip 555 can be coupled (e.g., optically, communicatively, operatively) to such an external optical component or device. [0112] In some examples, an optic fiber can be coupled (e.g., optically, communicatively, operatively) to the backend portion (e.g., an exposed backend portion) of the optical waveguide 520 at or proximate to the second end of the tapered fiber probe structure 510. For instance, the optic fiber can be directly coupled to the optical waveguide 520 at or proximate to the second end of the tapered fiber probe structure 510. In some examples, the optic fiber can be embodied as or include a polymer material. In other examples, the optic fiber can be embodied as or include a polycarbonate material. In some cases, the optic fiber can be embodied as an optical fiber or cable. In one example, the optic fiber can be embodied as a polymer optical waveguide (e.g., a PC core with a poly(methyl 2-methylpropenoate) cladding). In another example, the optic fiber can be embodied as a polymer optical waveguide (e.g., a PC core with a poly(methyl 2-methylpropenoate) cladding) having a diameter of 200 μm. In other examples, the backend connector region 560 can further include a fiber optic connector. In one example, the fiber optic connector can be embodied as a stainless steel fiber optic ferrule. For instance, the fiber optic connector can be embodied as a stainless steel fiber optic ferrule having an outer diameter of 1.25 mm. In one example, the fiber optic connector can be coupled to an optic fiber that can be coupled to the backend portion of the optical waveguide 520. [0113] The backend connector region 560 further includes a microfluidic tube 535 coupled (e.g., fluidly, operatively) to the microfluidic channel 530 at or proximate to the second end of the tapered fiber probe structure 510. In various examples, the microfluidic tube 535 can be coupled to a backend portion of the microfluidic channel 530 at or proximate to the second end of the tapered fiber probe structure 510 such that a tip portion of the microfluidic channel 530 at the first end of the tapered fiber probe structure 510 can be coupled (e.g., fluidly, operatively) to an external device. For instance, the microfluidic tube 535 can be coupled to the backend portion of the microfluidic channel 530 at or proximate to the second end of the tapered fiber probe structure 510 such that an opened crosscut portion of the microfluidic channel 530 at the angled tip 555 can be coupled (e.g., fluidly, operatively) to an external device. The microfluidic tube 535 in the example shown is at least partly inserted into the microfluidic channel 530 at the second end of the tapered fiber probe structure 510. In one example, the microfluidic tube 535 can be embodied as a polycarbonate (PC) tube. For instance, the microfluidic tube 535 can be embodied as a PC tube having a 150 μm OD and a 75 μm ID, although other OD and/or ID dimensions may be relied on in some cases. In other examples, the backend connector region 560 can further include a fluidic connector. In one example, the fluidic connector can be coupled to the microfluidic tube 535. Attorney Docket: 222204-2920 [0114] The backend connector region 560 further includes backend portions (e.g., exposed backend portions) of the tetrodes 540 (e.g., exposed backend portions of the electrodes 542, 544, 546, 548 of each of the tetrodes 540) extending from the second end of the tapered fiber probe structure 510. The backend portions of the tetrodes 540 (e.g., backend portions of the electrodes 542, 544, 546, 548 of each of the tetrodes 540) can be configured and operable for coupling (e.g., electrically, communicatively, operatively) to an external electrical component or device such that tip portions of the tetrodes 540 (e.g., tip portions of the electrodes 542, 544, 546, 548 of each of the tetrodes 540) at the first end of the tapered fiber probe structure 510 can be coupled (e.g., electrically, communicatively, operatively) to such an external electrical component or device. For instance, the backend portions of the tetrodes 540 can be configured and operable for coupling to an external electrical component or device such that an exposed crosscut surface of each of the tetrodes 540 (e.g., an exposed crosscut surface of each of the electrodes 542, 544, 546, 548 of each of the tetrodes 540) at the angled tip 555 can be coupled to such an external electrical component or device. [0115] In some examples, the backend connector region 560 can further include one or more electrical connectors respectively coupled (e.g., electrically, communicatively, operatively) to one or more of the tetrodes 540 (e.g., to the electrodes 542, 544, 546, 548 of one or more of the tetrodes 540) extending from the second end of the tapered fiber probe structure 510. In these examples, each of such electrical connectors can be coupled to a backend portion (e.g., an exposed backend portion) of a tetrode 540 (e.g., to exposed backend portions of the electrodes 542, 544, 546, 548 of the tetrode 540) at or proximate to the second end of the tapered fiber probe structure 510 such that a tip portion of the tetrode 540 (e.g., tip portions of the electrodes 542, 544, 546, 548 of the tetrode 540) at the first end of the tapered fiber probe structure 510 can be coupled (e.g., electrically, communicatively, operatively) to an external device. For instance, each of the electrical connectors can be coupled to a backend portion of each electrode 542, 544, 546, 548 of a tetrode 540 at or proximate to the second end of the tapered fiber probe structure 510 such that an exposed crosscut surface of the tetrode 540 (e.g., an exposed crosscut surface of each electrode 542, 544, 546, 548 of the tetrode 540) at the angled tip 555 can be coupled (e.g., electrically, communicatively, operatively) to an external device. In these examples, each of such electrical connectors can be directly coupled to one of the tetrodes 540 (e.g., to the electrodes 542, 544, 546, 548 of a tetrode 540) at or proximate to the second end of the tapered fiber probe structure 510. [0116] Any or all of the aforementioned electrical connectors that can be used in some examples can be embodied as a wire such as, for example, a copper wire. In one example, any or all of the electrical connectors can be embodied as an insulated copper wire. In one example, any or all of the Attorney Docket: 222204-2920 electrical connectors can be embodied as a 42AWG copper wire. In other examples, the backend connector region 560 can further include one or more pin connectors, a PCB, or any combination thereof. In one example, one end of each of the above-described electrical connectors can be coupled to the backend portion of a tetrode 540 (e.g., to an exposed backend portion of each electrode 542, 544, 546, 548 of the tetrode 540) at or proximate to the second end of the tapered fiber probe structure 510 and another end of the electrical connector can be coupled to a pin connector. In another example, one end of each of the electrical connectors can be coupled to the backend portion of a tetrode 540 (e.g., to an exposed backend portion of each electrode 542, 544, 546, 548 of the tetrode 540) at or proximate to the second end of the tapered fiber probe structure 510 and another end of the electrical connector can be coupled to a PCB. [0117] In some cases, the probe device 500 can further include a sealant to seal the microfluidic tube 535 to the microfluidic channel 530. For example, the probe device 500 can include a UV epoxy resin that can be coupled to the second end of the tapered fiber probe structure 510 and further coupled to the microfluidic tube 535 and/or the aforementioned fluidic connector. In some cases, the UV epoxy resin can be further coupled to any or all of the optical waveguide 520, the aforementioned optic fiber or fiber optic connector, the aforementioned electrical connectors, pin connectors, or PCB, or any combination thereof, to provide support for such components. [0118] The probe device 500 can be fabricated according to various dimensions, geometries, configurations, or any combination thereof. In some cases, the probe device 500 can be fabricated such that the optical waveguide 520, the microfluidic channel 530, and/or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548) are collocated within the tapered fiber probe structure 510 according to different arrangements. For example, the probe device 500 can be fabricated such that the optical waveguide 520, the microfluidic channel 530, and/or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548) are collocated within the tapered fiber probe structure 510 according to either of the probe component arrangements 600a or 600b described herein and illustrated in FIGS. 6A and 6B, respectively, or according to another probe component arrangement. [0119] FIGS.6A and 6B illustrate additional example probe component arrangements of another example multi-modal fiber probe device according to various aspects and embodiments of the present disclosure. FIGS.6A and 6B illustrate different example probe component arrangements that can be formed in a multi-modal fiber probe device of the present disclosure such as, for instance, the probe device 500 described herein with reference to FIGS.5A to 5C. FIG.6A illustrates an example probe component arrangement 600a according to various aspects and embodiments of the present disclosure. For instance, FIG.6A illustrates a cross-sectional view of an example tapered fiber probe Attorney Docket: 222204-2920 structure 510 formed according to the probe component arrangement 600a. For example, FIG. 6A illustrates a cross-sectional view at the tip region 550 and/or the angled tip 555 of an example tapered fiber probe structure 510 formed according to the probe component arrangement 600a. [0120] In the example shown, the tapered fiber probe structure 510 includes the optical waveguide 520, the microfluidic channel 530, and the tetrodes 540a, 540b, 540c (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) collocated within the tapered fiber probe structure 510 according to the probe component arrangement 600a illustrated in FIG. 6A. Only a single electrode 542a, 542b, 542c is respectively denoted for each of the tetrodes 540a, 540b, 540c in FIG. 6A for clarity. In the probe component arrangement 600a, the optical waveguide 520, the microfluidic channel 530, and the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548) are parallel to and coplanar with one another along the longitudinal axis of the tapered fiber probe structure 510 from the first end (e.g., first distal end) to the second end (e.g., second distal end) of the tapered fiber probe structure 510. For instance, centerlines of the optical waveguide 520, the microfluidic channel 530, and the tetrodes 540 (e.g., a collective centerline of the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) are parallel or approximately parallel to and/or coplanar or approximately coplanar with one another along the longitudinal axis of the tapered fiber probe structure 510 from the first end to the second end of the tapered fiber probe structure 510 in the probe component arrangement 600a shown in FIG.6A. In this example, the longitudinal axis of the tapered fiber probe structure 510 is located at a center of the tapered fiber probe structure 510 and it extends into and out of the page of FIG.6A in a direction that is parallel to an axis “Z.” [0121] The tapered fiber probe structure 510 can further include one or more divider regions positioned between at least two of any of the optical waveguide 520, the microfluidic channel 530, or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of the tetrodes 540a, 540b, 540c). In the example shown, the tapered fiber probe structure 510 includes divider regions 615a, 615b. In this example, the divider region 615a is positioned between the optical waveguide 520 and the microfluidic channel 530. The divider region 615a in this example is located between such probe components and it extends from the first end to the second end of the tapered fiber probe structure 510. For instance, the divider region 615a extends into and out of the page of FIG.6A from the first end to the second end of the tapered fiber probe structure 510 in a direction that is parallel to the “Z” axis. The divider region 615a isolates (e.g., physically) and insulates (e.g., electrically, optically, electromagnetically, chemically) the optical waveguide 520 from at least one of the microfluidic channel 530 or any or all of the electrodes 542, 544, 546, 548 of any or all of the tetrodes 540a, 540b, 540c. The divider region 615a includes material from one or more portions of at least one of the Attorney Docket: 222204-2920 tapered fiber probe structure 510 (e.g., polymer or polycarbonate used to form the tapered fiber probe structure 510), the optical waveguide 520 (e.g., cladding, sheath, wrap, or coating of the optical waveguide 520), or the microfluidic channels 530 (e.g., polymer or polycarbonate tubes used to form the microfluidic channel 530). [0122] In the example shown, the divider region 615b is positioned between the microfluidic channel 530 and the tetrode 540c (e.g., the electrodes 544c, 546c of the tetrode 540c). The divider region 615b in this example is located between such probe components and it extends from the first end to the second end of the tapered fiber probe structure 510. For instance, the divider region 615b extends into and out of the page of FIG.6A from the first end to the second end of the tapered fiber probe structure 510 in a direction that is parallel to the “Z” axis. The divider region 615b isolates (e.g., physically) and insulates (e.g., electrically, optically, electromagnetically, chemically) any or all of the electrodes 542, 544, 546, 548 of any or all of the tetrodes 540a, 540b, 540c from at least one of the optical waveguide 520 or the microfluidic channel 530. The divider region 615b includes material from one or more portions of at least one of the tapered fiber probe structure 510 (e.g., polymer or polycarbonate used to form the tapered fiber probe structure 510), the microfluidic channel 530 (e.g., polymer or polycarbonate tubes used to at least partly form the microfluidic channel 530), or one or more of the electrodes 542, 544, 546, 548 (e.g., an insulating coating, wrap, sheath, or jacket of one or both of the electrodes 544c, 546c). [0123] The tapered fiber probe structure 510 in this example further includes additional divider regions positioned between pairs of the tetrodes 540 (e.g., between the electrodes 542, 544, 546, 548 of the tetrodes 540a, 540b, 540c). These additional divider regions isolate (e.g., physically) and insulate (e.g., electrically, electromagnetically) the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of the tetrodes 540a, 540b, 540c) from one another. The additional divider regions include material from one or more portions of at least one of the tapered fiber probe structure 510 (e.g., polymer or polycarbonate used to form the tapered fiber probe structure 510) or the tetrodes 540 (e.g., an insulating coating, wrap, sheath, or jacket of any or all of the electrodes 542, 544, 546, 548). [0124] FIG. 6B illustrates another example probe component arrangement 600b according to various aspects and embodiments of the present disclosure. For instance, FIG.6B illustrates a cross- sectional view of an example tapered fiber probe structure 510 formed according to the probe component arrangement 600b. For example, FIG. 6B illustrates a cross-sectional view at the tip region 550 and/or the angled tip 555 of an example tapered fiber probe structure 510 formed according to the probe component arrangement 600b. The probe component arrangement 600b is an example alternative embodiment of the probe component arrangement 600a described herein and Attorney Docket: 222204-2920 illustrated in FIG. 6A. A difference between the probe component arrangement 600b and the probe component arrangement 600a is that the probe component arrangement 600b includes an additional tetrode 540d in place of the microfluidic channel 530. The tetrode 540d includes additional electrodes 542d, 544d, 546d, 548d. Only a single electrode 542d of the tetrode 540d is denoted in FIG. 6B for clarity. The tetrode 540d can include the same or similar structure, components, features, materials, and functionality as that of any or all of the tetrodes 540a, 540b, 540c. The electrodes 542d, 544d, 546d, 548d can include the same or similar structure, components, features, materials, and functionality as that of any or all of the electrodes 542, 544, 546, 548 of any or all of the tetrodes 540a, 540b, 540c. [0125] In the example shown, the tapered fiber probe structure 510 includes the optical waveguide 520 and the tetrodes 540a, 540b, 540c, 540d (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c, 540d) collocated within the tapered fiber probe structure 510 according to the probe component arrangement 600b illustrated in FIG. 6B. Only a single electrode 542a, 542b, 542c, 542d is respectively denoted for each of the tetrodes 540a, 540b, 540c, 540d in FIG. 6B for clarity. In the probe component arrangement 600b, the optical waveguide 520 and the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548) are parallel to and coplanar with one another along the longitudinal axis of the tapered fiber probe structure 510 from the first end (e.g., first distal end) to the second end (e.g., second distal end) of the tapered fiber probe structure 510. For instance, centerlines of the optical waveguide 520 and the tetrodes 540 (e.g., a collective centerline of the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c, 540d) are parallel or approximately parallel to and/or coplanar or approximately coplanar with one another along the longitudinal axis of the tapered fiber probe structure 510 from the first end to the second end of the tapered fiber probe structure 510 in the probe component arrangement 600b shown in FIG. 6B. In this example, the longitudinal axis of the tapered fiber probe structure 510 is located at a center of the tapered fiber probe structure 510 and it extends into and out of the page of FIG.6B in a direction that is parallel to an axis “Z.” [0126] The tapered fiber probe structure 510 can further include one or more divider regions positioned between at least two of any of the optical waveguide 520 or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of the tetrodes 540a, 540b, 540c). In the example shown, the tapered fiber probe structure 110 further includes a divider region 615 positioned between the optical waveguide 520 and the tetrode 540d (e.g., the electrodes 544d, 546d of the tetrode 540d). The divider region 615 in this example is located between such probe components and it extends from the first end to the second end of the tapered fiber probe structure 510. For instance, the divider region 615 Attorney Docket: 222204-2920 extends into and out of the page of FIG. 6B from the first end to the second end of the tapered fiber probe structure 510 in a direction that is parallel to the “Z” axis. The divider region 615 isolates (e.g., physically) and insulates (e.g., electrically, optically, electromagnetically, chemically) the optical waveguide 520 from any or all of the electrodes 542, 544, 546, 548 of any or all of the tetrodes 540a, 540b, 540c, 540d and vice versa. The divider region 615 includes material from one or more portions of at least one of the tapered fiber probe structure 510 (e.g., polymer or polycarbonate used to form the tapered fiber probe structure 510), the optical waveguide 520 (e.g., cladding, sheath, wrap, or coating of the optical waveguide 520), or one or more of the electrodes 542, 544, 546, 548 (e.g., an insulating coating, wrap, sheath, or jacket of one or both of the electrodes 544d, 546d). [0127] The tapered fiber probe structure 510 in this example further includes additional divider regions positioned between pairs of the tetrodes 540 (e.g., between the electrodes 542, 544, 546, 548 of the tetrodes 540a, 540b, 540c, 540d). These additional divider regions isolate (e.g., physically) and insulate (e.g., electrically, electromagnetically) the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of the tetrodes 540a, 540b, 540c, 540d) from one another. The additional divider regions include material from one or more portions of at least one of the tapered fiber probe structure 510 (e.g., polymer or polycarbonate used to form the tapered fiber probe structure 510) or the tetrodes 540 (e.g., an insulating coating, wrap, sheath, or jacket of any or all of the electrodes 542, 544, 546, 548). [0128] FIGS.7A, 7B, 7C, and 7D collectively illustrate another example fabrication process for fabricating various multi-modal fiber probe devices of the present disclosure. FIG. 7A illustrates another example preform fabrication process 700a according to various aspects and embodiments of the present disclosure. The preform fabrication process 700a illustrated in FIG. 7A, or a variation thereof, can be used to fabricate various preforms that can each then be used to fabricate a fiber probe structure of a multi-modal fiber probe device described herein. The preform fabrication process 700a, or a variation thereof, can be implemented to fabricate a preform that can then be used to fabricate a fiber probe structure of a multi-modal fiber probe device described herein according to various dimensions, geometries, configurations, or any combination thereof. For example, the preform fabrication process 700a, or a variation thereof, can be implemented to fabricate a preform that can then be used to fabricate the tapered fiber probe structure 510 of the probe device 500 of FIGS. 5A to 5C such that the optical waveguide 520, the microfluidic channel 530, and/or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) are formed in the tapered fiber probe structure 510 according to either of the probe component arrangements 600a, 600b Attorney Docket: 222204-2920 described herein and illustrated in FIGS. 6A and 6B, respectively, or according to another probe component arrangement. [0129] FIG. 7A shows example fabrication steps of the preform fabrication process 700a that can be implemented as described herein to form various preforms such as, for instance, a preform 705 shown in this example. In some cases, the preform 705 can be used to form a mini-preform 709a then a mini-preform 709b, which can then be used to form the tapered fiber probe structure 510 as described herein with reference to FIGS.7B and 7C. [0130] The preform fabrication process 700a can include forming one or more channels 730 in and/or through preform material such as, for instance, a rectangular preform or one or more preform plates. The preform 705 can be created by milling (e.g., using a CNC milling machine) or otherwise forming multiple grooves or channels in one or more PC plates (e.g., rectangular-shaped PC plates). In one example, a first portion (e.g., half) of each of such grooves or channels may be milled into a first PC plate (e.g., first rectangular-shaped PC plate). In this example, a second portion (e.g., half) of each of such grooves or channels may be milled in a second PC plate (e.g., second rectangular- shaped PC plate) such that the first and second portions of each of the grooves or channels are aligned when the first and second PC plates are positioned (e.g., stacked) on one another to form the preform 705. In another example, the preform 705 can be created by milling or otherwise forming multiple grooves or channels in a first rectangular-shaped PC plate and stacking one or more additional rectangular-shaped PC plates on at least one side or surface of the first PC plate (e.g., a top or bottom side or surface). Either or both of the aforementioned rectangular preforms can then be respectively processed into a mini-preform 709a then a mini-preform 709b, which can then be used to form the tapered fiber probe structure 510 as described herein with reference to FIGS. 7B and 7C. The channels 730 can be formed to various cross-sectional geometries, configurations, and dimensions within and through the preform 705. For instance, any or all of the channels 730 can be formed to have a circular-shaped cross-section, rectangular-shaped cross-section, a circular-shaped cross- section, a triangular-shaped cross-section, another cross-section geometry, or any combination thereof. [0131] Consolidation of the above-described preform materials (e.g., PC plates having grooves or channels) to form the preform 705 can be performed in some examples by heating such preform materials under vacuum at, for instance, approximately 190 °C. In some examples, polymer materials (e.g., PC films, tubes, rods, preforms, and mini-preforms) used to fabricate the preform 705 can be baked under vacuum at, for instance, approximately 80°C to ensure they are moisture free. A finalized preform 705 can have a width (w) of approximately 30 mm in one example. In another example, the Attorney Docket: 222204-2920 preform 705 can be heated and drawn down to a fiber (e.g., the mini-preform 709a) having a width (w) of approximately 2 mm as described herein and illustrated in FIG.7B. [0132] FIG. 7B illustrates another example thermal drawing process 700b according to various aspects and embodiments of the present disclosure. The thermal drawing process 700b illustrated in FIG.7B, or a variation thereof, can be used to fabricate various mini-preforms that can each then be used to fabricate a fiber probe structure of a multi-modal fiber probe device described herein. The thermal drawing process 700b, or a variation thereof, can be implemented to fabricate a mini-preform that can then be used to fabricate a fiber probe structure of a multi-modal fiber probe device described herein according to various dimensions, geometries, configurations, or any combination thereof. For example, the thermal drawing process 700b, or a variation thereof, can be implemented to fabricate a mini-preform that can then be used to fabricate the tapered fiber probe structure 510 of the probe device 500 of FIGS. 5A to 5C such that the optical waveguide 520, the microfluidic channel 530, and/or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) are formed in the tapered fiber probe structure 510 according to either of the probe component arrangements 600a, 600b described herein and illustrated in FIGS. 6A and 6B, respectively, or according to another probe component arrangement. [0133] In various examples, the thermal drawing process 700b can be implemented to form a mini-preform 709a from a preform 705 that has been fabricated using the preform fabrication process 700a described herein and illustrated in FIG. 7A. In these or other examples, the thermal drawing process 700b can be implemented to form the mini-preform 709a such that the channels 730 of the preform 705 are formed in the mini-preform 709a in the same or similar manner as they are formed in the preform 705. For instance, the thermal drawing process 700b can be implemented to form the mini-preform 709a such that each of the channels 730 is formed in the mini-preform 709a with the same or similar cross-sectional geometry and relative position as in the preform 705. [0134] The thermal drawing process 700b can include heating and pulling the preform 705. For example, the preform 705 can be heated in a furnace and pulled into a fiber 707 (e.g., an optical fiber) using, for instance, a capstan motor. The furnace can be divided into a top section, a middle section, and a bottom section that can be individually set to different temperatures. The top section of the furnace can be where the preform 705 is preheated. The middle section of the furnace can be where the preform 705 is softened and pulled into the fiber 707. The bottom section of the furnace can be where the resulting fiber 707 is cooled. In one example, the top, middle, and bottom sections of the furnace can be set to 150°C, 275°C, and 120°C, respectively. In some examples the temperature of the preform 705 in any given section of the furnace during the thermal drawing process 700b is the Attorney Docket: 222204-2920 same or approximately the same as the temperature of such a furnace section. In other examples the temperature of the preform 705 in any given section of the furnace during the thermal drawing process 700b is different from the temperature of such a furnace section. [0135] In some examples, the cross-sectional dimensions (e.g., width, height or thickness) of the fiber 707 being formed during the thermal drawing process 700b can be closely monitored using a laser micrometer. The cross-sectional dimensions (e.g., width, height or thickness) of the fiber 707 can also be controlled during the thermal drawing process 700b by adjusting the pulling speed of the capstan motor and/or the temperature of one or more sections of the furnace. In the example shown, the thermal drawing process 700b can further include cutting the fiber 707 to form one or more mini- preforms 709a. In one example, the thermal drawing process 700b can include pulling the preform 705 having a width (w) of approximately 30 mm into the fiber 707 such that the fiber 707 and the mini-preform 709a each have a width (w) of approximately 2 mm. The fiber 707 can then be cut into, for example, one or more 10 cm long mini-preforms 709a that can each be used for the thermal tapering process 700c described herein with reference to FIG.7C. [0136] FIG. 7C illustrates another example thermal tapering process 700c according to various aspects and embodiments of the present disclosure. The thermal tapering process 700c may be implemented and referred to herein as a convergence tapering process. The thermal tapering process 700c illustrated in FIG. 7C, or a variation thereof, can be used to fabricate various fiber probe structures of different multi-modal fiber probe devices described herein. The thermal tapering process 700c, or a variation thereof, can be implemented to fabricate a fiber probe structure of a multi-modal fiber probe device described herein according to various dimensions, geometries, configurations, or any combination thereof. For example, the thermal tapering process 700c, or a variation thereof, can be implemented to fabricate the tapered fiber probe structure 510 of the probe device 500 of FIGS. 5A to 5C such that the optical waveguide 520, the microfluidic channel 530, and/or the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) are formed in the tapered fiber probe structure 510 according to either of the probe component arrangements 600a, 600b described herein and illustrated in FIGS.6A and 6B, respectively, or according to another probe component arrangement. [0137] In various examples, the thermal tapering process 700c can be implemented to form a fiber probe structure from a mini-preform that has been fabricated from a preform using the preform fabrication process 700a and the thermal drawing process 700b described herein and illustrated in FIGS.7A and 7B, respectively. In these or other examples, the thermal tapering process 700c can be implemented to form the fiber probe structure such that the optical waveguides, microfluidic Attorney Docket: 222204-2920 channels, and/or tetrodes (e.g., electrodes of each tetrode) of the preform and mini-preform are formed in the fiber probe structure in the same or similar manner as they are formed in the preform and the mini-preform. For instance, the thermal tapering process 700c can be implemented to form the fiber probe structure such that each of the optical waveguides, microfluidic channels, and tetrodes (e.g., electrodes of each tetrode) is formed in the fiber probe structure with the same or similar cross- sectional geometry and relative position as in each of the preform and the mini-preform. For example, the thermal tapering process 700c can be implemented to form the fiber probe structure such that each of the optical waveguides, microfluidic channels, and tetrodes (e.g., electrodes of each tetrode) is formed in a reduced cross-section region created in the mini-preform and/or at a tip region of the fiber probe structure with the same or similar cross-sectional geometry and relative position as in each of the preform and the mini-preform. [0138] FIG. 7C shows example fabrication steps of the thermal tapering process 700c that can be implemented as described herein to form various fiber probe structures such as, for instance, the tapered fiber probe structure 510 shown in this example. The tapered fiber probe structure 510 in this example can be formed from the mini-preform 709b described herein and illustrated in FIG.7B. The thermal tapering process 700c can be implemented to form the tapered fiber probe structure 510 such that the optical waveguide 520, the microfluidic channel 530, and the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) are formed in the tapered fiber probe structure 510 in the same or similar manner as the optical waveguide 720, the channel 730, and the tetrodes 740 (e.g., the electrodes 742, 744, 746, 748 of each of the tetrodes 740a, 740b, 740c) are formed in the mini-preform 709b, for instance, with the same or similar cross-sectional geometry and relative position as in the mini-preform 709b. Implementation of the thermal tapering process 700c in this example results in the formation of the optical waveguide 520, the microfluidic channel 530, and the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) from the optical waveguide 720, the channel 730, and the tetrodes 740 (e.g., the electrodes 742, 744, 746, 748 of each of the tetrodes 740a, 740b, 740c), respectively. In this example, the thermal tapering process 700c can be implemented to form the tapered fiber probe structure 510 such that each of the optical waveguide 520, the microfluidic channel 530, and the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) is formed in a reduced cross-section region 750 created in the mini-preform 709b and/or at the tip region 550 of the tapered fiber probe structure 510 with the same or similar cross-sectional geometry and relative position as in the mini-preform 709b. Attorney Docket: 222204-2920 [0139] At 702c, the thermal tapering process 700c can include respectively inserting one or more probe components such as, for example, one or more optical waveguides 720 and/or one or more tetrodes 740a, 740b, 740c (or “tetrodes 740”) into and through one or more of the channels 730 of the mini-preform 709a to create a mini-preform 709b as illustrated in FIG.7C. In the example shown, each of the tetrodes 740 includes electrodes 742, 744, 746, 748. In this example, the optical waveguide 720 can be embodied as and include the same or similar structure, components, material, and functionality as that of the optical waveguide 520. In this example, the tetrodes 740a, 740b, 740c can be embodied as and include the same or similar structure, components, material, and functionality as that of the tetrodes 540a, 540b, 540c, respectively. In this example, the electrodes 742, 744, 746, 748 can be embodied as and include the same or similar structure, components, material, and functionality as that of the electrodes 542, 544, 546, 548. The optical waveguide 720 and the tetrodes 740 (e.g., the electrodes 742, 744, 746, 748 of each of the tetrodes 740a, 740b, 740c) can be respectively formed into the optical waveguide 520 and the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) as described herein. [0140] In one example, an optical waveguide 720 with a PC core (e.g., having a refractive index n =1.586) and a poly(methyl 2-methylpropenoate) (PMMA; having a refractive index n = 1.49) cladding can be inserted into a channel 730 of the preform 705 at 702c of the thermal tapering process 700c. In another example, electrodes 742, 744, 746, 748 embodied as at least one of a bismuth tin (BiSn) alloy material, a nichrome (NiCr) alloy material, a stainless steel alloy material, a gold or gold alloy material, a platinum or platinum alloy material, a tungsten or tungsten alloy material, or another material or alloy are grouped into tetrodes 740a, 740b, 740c and inserted into respective channels 730 of the preform 705 at 702c of the thermal tapering process 700c. In some cases, a PC microfluidic tube may be inserted into one of the channels 730 at 702c of the thermal tapering process 700c. In these cases, the PC microfluidic tube may be formed into the microfluidic channel 530 of the tapered fiber probe structure 510 as described herein. In other examples, one of the channels 730 may remain empty in each of the mini-preforms 709a, 709b. In these examples, the empty channel 730 may be formed into the microfluidic channel 530 of the tapered fiber probe structure 510 as described herein. [0141] Similar to a glass pipette pulling process, at 704c of the thermal tapering process 700c the mini-preform 709b can be heated until it is softened, then pulled in opposite directions to create the reduced cross-section region 750 in the mini-preform 709b as illustrated in FIG.7C. At 704c, the thermal tapering process 700c can include holding the mini-preform 709b in place and/or adjusting the alignment of the mini-preform 709b using opto-mechanical components. The thermal tapering Attorney Docket: 222204-2920 process 700c can further include heating and softening the mini-preform 709b using a furnace set to, for instance, approximately 230°C. In some examples the temperature of the mini-preform 709b in the furnace during the thermal tapering process 700c is the same or approximately the same as the temperature of the furnace. In other examples the temperature of the mini-preform 709b in the furnace during the thermal tapering process 700c is different from the temperature of the furnace. [0142] Once the mini-preform 709b is softened to a desired degree, it can be pulled in opposite directions, for example, by a computer controlled linear motor to transform the mini-preform 709b into a tapered mini-preform structure 710 having the reduced cross-section region 750. The speed and/or travel distance of the linear motor can be altered to adjust the resulting geometry or area (e.g., width, height or thickness) of the reduced cross-section region 750. The resulting geometry or area (e.g., width, height or thickness) of the reduced cross-section region 750 can be closely monitored during the thermal tapering process 700c by using a laser micrometer. The resulting geometry or area (e.g., width, height or thickness) of the reduced cross-section region 750 can also be controlled during the thermal tapering process 700c by adjusting the pulling speed of the linear motor and/or the temperature of the furnace. [0143] At 704c the thermal tapering process 700c can further include cutting the reduced cross- section region 750 of the tapered mini-preform structure 710 at a desired angle (^) to produce two individual tapered fiber probe structures 510. For instance, after softening and pulling the mini- perform 709b, the resulting tapered mini-preform structure 710 can be cut at a desired location along the reduced cross-section region 750 to produce two individual tapered fiber probe structures 510. To produce the tapered fiber probe structure 510 such that it has a tip region 550 that minimally damages tissue when inserted into a subject (e.g., a patient, person, animal), the reduced cross-section region 750 can be cut with a crosscut 711 at a defined angle (^) to create the angled tip 555 of the tapered fiber probe structure 510. For example, the reduced cross-section region 750 can be crosscut at a defined angle (^) relative to a longitudinal axis or a cross-section of at least one of the reduced cross-section region 750, the mini-preform 709b, or the tapered mini-preform structure 710 at any location along the reduced cross-section region 750 to form the angled tip 555 of the tapered fiber probe structure 510. [0144] FIG. 7D illustrates another example backend connection process 700d according to various aspects and embodiments of the present disclosure. The backend connection process 700d illustrated in FIG.7D, or a variation thereof, can be used to fabricate various multi-modal fiber probe devices described herein. For instance, the backend connection process 700d can be implemented to fabricate a backend connector region of a multi-modal fiber probe device described herein such as, Attorney Docket: 222204-2920 for instance, the backend connector region 560 of the probe device 500. In some cases, the backend connection process 700d of FIG.7D can include the use of translation stages and a digital microscope to provide finer position control during connection. In one example, the backend connection process 700d can be implemented as described herein with reference to FIG.7D. [0145] The backend connection process 700d can include coupling (e.g., fluidly, communicatively, operatively) the microfluidic tube 535 to the microfluidic channel 530 located at or proximate to the second end of the tapered fiber probe structure 510. For instance, the microfluidic tube 535 can be coupled to the channel 730 formed in the tapered mini-preform structure 710 as described herein with reference to the preform fabrication process 700a, the thermal drawing process 700b, and the thermal tapering process 700c respectively illustrated in FIGS. 7A, 7B, and 7C. The microfluidic connection of the microfluidic tube 535 to the microfluidic channel 530 can be achieved in one example by inserting a drawn microfluidic tube 535 embodied as a drawn PC tube into the microfluidic channel 530 located in the tapered fiber probe structure 510 at its second end. In one example, the microfluidic tube 535 can be embodied as a PC tube having an OD of approximately 150 μm and an ID of approximately 75 μm, although other PC tubes having other ODs and/or IDs can used in some cases. [0146] In some cases, the backend connection process 700d can further include coupling (e.g., optically, communicatively, operatively) an optic fiber to a backend portion (e.g., an exposed backend portion) of the optical waveguide 520 at or proximate to the second end of the tapered fiber probe structure 510. For instance, the optic fiber can be coupled to a backend portion (e.g., exposed backend portion) of the optical waveguide 720 formed in the tapered mini-preform structure 710 as described herein with reference to the preform fabrication process 700a, the thermal drawing process 700b, and the thermal tapering process 700c respectively illustrated in FIGS. 7A, 7B, and 7C. The optic connection of the optic fiber to the optical waveguide 520 can be achieved in one example by coupling a drawn optic fiber embodied as a drawn polymer optical fiber (e.g., a PC core with a poly(methyl 2-methylpropenoate) cladding) to the optical waveguide 520 located in the tapered fiber probe structure 510 at its second end. In one example, the optic fiber can be embodied as a polymer optical fiber having a diameter of approximately 200 μm. In one example, the optic fiber can be embodied as a polymer optical fiber that can be coupled to the optical waveguide 520 via a stainless steel fiber optic ferrule during the backend connection process 700d. In some cases, the optic fiber can be embodied as a polymer optical fiber that can be polished using, for instance, 30-1 μm grit sandpaper prior to being coupled to the optical waveguide 520. Attorney Docket: 222204-2920 [0147] In some cases, the backend connection process 700d can further include coupling (e.g., electrically, operatively) electrical connectors to the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) located at or proximate to the second end of the tapered fiber probe structure 510. For instance, the electrical connectors can be coupled to the tetrodes 740 (e.g., the electrodes 742, 744, 746, 748 of each of the tetrodes 740a, 740b, 740c) formed in the tapered mini-preform structure 710 as described herein with reference to the preform fabrication process 700a, the thermal drawing process 700b, and the thermal tapering process 700c respectively illustrated in FIGS. 7A, 7B, and 7C. The electrical connection of the electrical connectors to the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) can be achieved in one example by heating the second end of the tapered fiber probe structure 510 to approximately 160°C to melt portions of the tetrodes 540 (e.g., portions of the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) located in this region of the tapered fiber probe structure 510 to a desired melted state. This temperature (e.g., 160°C) is high enough to melt the tetrodes 540 (e.g., the electrodes 542, 544, 546, 548 of each of the tetrodes 540a, 540b, 540c) but low enough to avoid damaging the tapered fiber probe structure 510. In one example, each of such electrical connectors can be embodied as a copper wire (e.g., an insulated copper wire) that can be inserted into one of the melted electrodes 542, 544, 546, 548 of a tetrode 540 located in the tapered fiber probe structure 510 at its second end. In some cases, the electrical connectors (e.g., copper wires) can be guided by a hypodermic needle when lowered into the melted electrodes 542, 544, 546, 548. The second end of the tapered fiber probe structure 510 can then be cooled to allow the electrodes 542, 544, 546, 548 and the electrical connectors to solidify. [0148] In some cases, the backend connection process 700d can also include using a UV epoxy resin to seal and fix at least one of the aforementioned electrical, microfluidic, or optical connections in place. By completing the backend connection process 700d illustrated in FIG. 7D, a multi-modal fiber probe device described herein can be fitted with industry standard adapters compatible with electrophysiology equipment, optical modules, and drug delivery pumps. [0149] FIGS.8A and 8B illustrate views of another example multi-modal fiber probe device 800 (or “probe device 800”) according to various aspects and embodiments of the present disclosure. FIG.8A illustrates a top view of the example multi-modal fiber probe device 800 according to various aspects and embodiments of the present disclosure. FIG. 8B illustrates an isometric view of a tip region 850 of the example multi-modal fiber probe device 800 according to various aspects and embodiments of the present disclosure. The probe device 800 can be designed, embodied, and implemented as a flexible, multi-modal neural fiber probe device in examples herein. For instance, Attorney Docket: 222204-2920 the probe device 800 can be designed, embodied, and implemented as a fiber Photometry, Drug delivery, Optical stimulation, and Electrophysiology (P-DOpE) probe device described in various embodiments herein. [0150] Similar to the probe devices 100 and 500, the probe device 800 offers relatively higher complexities at a tip region compared to existing devices while also easing the connection between a backend connector region and external electronics that may be coupled to the probe device 800. Additionally, the probe device 800 can be implemented to concurrently (e.g., simultaneously) perform various electrophysiology and fiber photometry operations in a subject (e.g., a patient, person, animal). For instance, the probe device 800 can be implemented to perform simultaneous electrophysiology and fiber photometry in such a subject, thereby allowing for the cross-referencing of electrical and optical signals in the subject. The probe device 800 can be designed and embodied as a fiber P-DOpE probe device described herein that has a relatively high spatial and temporal resolution and is capable of detecting both electrical and chemical signals. [0151] The probe device 800 is an example alternative embodiment of the probe device 500 described herein and illustrated in FIGS. 5A to 5C. The probe device 800 can include the same or similar structure, components, features, materials, and functionality as that of the probe device 500. A difference between the probe device 800 and the probe device 500 is that the cross-sectional geometry, for example, the width (w) and thickness (t) of a fiber probe structure of the probe device 800 is uniform from a first end to a second end of such a fiber probe structure, as opposed to tapered. Another difference between the probe device 800 and the probe device 500 is that the probe device 800 includes a silica-based optical waveguide, as opposed to a polymer or polycarbonate-based optical waveguide. Another difference between the probe device 800 and the probe device 500 is that the silica-based optical waveguide and tetrodes (e.g., electrodes of each tetrode) of the probe device 800 have a relatively higher melting temperature compared to that of a polymer-based fiber probe structure of the probe device 800 in which the waveguide and tetrodes are integrated. This difference in melting temperatures between the fiber probe structure and the probe components integrated therein allows for the probe device 800 to be fabricated in a different manner compared to the probe device 500. The difference in melting temperatures and fabrication methods allows for the fiber probe structure of the probe device 800 to be formed with a uniform cross-section (e.g., width and thickness) extending from a first end to a second end of the probe device 800. [0152] The probe device 800 illustrated in FIGS. 8A and 8B includes a fiber probe structure 810. The fiber probe structure 810 can be embodied and implemented as a flexible fiber probe structure as described in examples herein. The fiber probe structure 810 can include one or more Attorney Docket: 222204-2920 optical waveguides 820, one or more microfluidic channels 830, one or more tetrodes 840a, 840b, 840c (or “tetrodes 840”), or any combination thereof. In the example shown, the fiber probe structure 810 includes a single silica optical waveguide 820 and a single microfluidic channel 830. In this example, each of the tetrodes 840 is embodied as and thus includes electrodes 842, 844, 846, 848. For instance, the tetrode 840a is embodied as and includes electrodes 842a, 844a, 846a, 848a, the tetrode 840b is embodied as and includes electrodes 842b, 844b, 846b, 848b, and the tetrode 840c is embodied as and includes electrodes 842c, 844c, 846c, 848c. Only a single electrode 842a, 842b, 842c is respectively denoted for the tetrodes 840a, 840b, 840c in FIGS. 8A and 8B for clarity. The silica optical waveguide 820, the microfluidic channel 830, and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848) can be formed in the fiber probe structure 810 such that they are collocated approximately parallel to and extend along a longitudinal axis of the fiber probe structure 810 from a first end (e.g., a first distal end) to a second end (e.g., a second distal end) of the fiber probe structure 810 as illustrated collectively across FIGS. 8A and 8B. For instance, centerlines of the silica optical waveguide 820, the microfluidic channel 830, and the tetrodes 840 can be parallel to and coplanar or approximately coplanar with one another along the longitudinal axis of the fiber probe structure 810 from the first end to the second end of the fiber probe structure 810. [0153] The first end and the second end of the fiber probe structure 810 can each be formed to a width (w) ranging between, for instance, approximately 70 μm to approximately 750 μm. In one embodiment, the first end and the second end of the fiber probe structure 810 can each have a width (w) of approximately 500 μm. The first end and the second end of the fiber probe structure 810 can have a thickness (t) ranging between, for instance, approximately 70 μm to approximately 250 μm. In one embodiment, the first end and the second end of the fiber probe structure 810 can have a thickness (t) of approximately 100 μm. [0154] In the example shown, the fiber probe structure 810 is embodied with a rectangular shape and rectangular cross-section. In various embodiments, a cross-section of the first end of the fiber probe structure 810 and a corresponding cross-section of the second end of the fiber probe structure 810 are each embodied as a rectangular-shaped cross-section. For instance, a cross-section taken at or proximate to the first end of the fiber probe structure 810 that is normal to the longitudinal axis of the fiber probe structure 810 and a corresponding cross-section taken at or proximate to the second end of the fiber probe structure 810 that is also normal to the longitudinal axis of the fiber probe structure 810 are both rectangular-shaped cross-sections in the example shown. [0155] Although the fiber probe structure 810 illustrated in FIGS. 8A and 8B is embodied with a rectangular shape and rectangular cross-section, the scope of the present disclosure is not so limited. Attorney Docket: 222204-2920 In other examples the fiber probe structure 810 may be embodied such that it has a circular-shaped cross-section, an annular-shaped cross-section, a triangular-shaped cross-section, a square-shaped cross-section, or a cross-section having another geometry. In some embodiments, a cross-section of the first end of the fiber probe structure 810 and a corresponding cross-section of the second end of the fiber probe structure 810 are each embodied as a circular-shaped cross-section, an annular-shaped cross-section, a triangular-shaped cross-section, a square-shaped cross-section, or a cross-section having another geometry. [0156] The fiber probe structure 810 can be formed using and can thus include one or more preform materials used to fabricate fiber probe structures such as, for instance, at least one of a polymer material or a polycarbonate (PC) material. In some examples, the fiber probe structure 810 can be formed using one or more polymer or PC plates having grooves or channels in which optical waveguides and electrodes can be inserted, and in which microfluidic channels can be formed as described in examples herein. In some cases, the fiber probe structure 810 can be formed from a rectangular PC preform that can be created by milling or otherwise forming multiple grooves or channels in a PC plate. In one example, a first portion (e.g., half) of each of such grooves or channels may be milled into a first PC plate and a second portion (e.g., half) of each of such grooves or channels may be milled in a second PC plate such that the first and second portions of each of the grooves or channels are aligned when the first and second PC plates are positioned (e.g., stacked) on one another to form the rectangular PC preform. In another example, the fiber probe structure 810 can be formed from a rectangular PC preform that can be created by milling or otherwise forming multiple grooves or channels in a PC plate and stacking one or more additional PC plates on at least one side or surface of the PC plate (e.g., a top or bottom side or surface) to form the rectangular PC preform. Either or both of the aforementioned rectangular preforms can then be respectively processed into a mini-preform that can be used to create the fiber probe structure 810 as described further in examples herein. [0157] The silica optical waveguide 820 can be configured and operable to control optogenetics. In some examples, the silica optical waveguide 820 can be embodied as or include at least one of a silicon or a silica material. In some cases, the silica optical waveguide 820 can be embodied as at least one of a silica optical fiber waveguide, a silica fiber, a silica-silica fiber, or another silica-based optical fiber. For instance, the silica optical waveguide 820 can be embodied as or include a silica optical fiber having a silica glass core and a silica glass cladding with a refractive index that is lower than that of the silica glass core. In the example shown, a cross-sectional area of the silica optical waveguide 820 at the first end of the fiber probe structure 810 equals a corresponding cross-sectional Attorney Docket: 222204-2920 area of the optical waveguide 820 at or proximate to the second end of the fiber probe structure 810. For instance, the size of a cross-sectional area of the silica optical waveguide 820 at the first end of the fiber probe structure 810 is the same as or approximately the same as that of a corresponding cross-sectional area of the optical waveguide 820 at or proximate to the second end of the fiber probe structure 810. For example, the cross-sectional area of the silica optical waveguide 820 is uniform or approximately uniform throughout its length. The silica optical waveguide 820 can have a diameter ranging between, for instance, approximately 5 μm to approximately 300 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, the silica optical waveguide 820 of the probe device 800 can have a diameter of approximately 50 μm. [0158] The microfluidic channel 830 can be configured and operable to allow for focal drug infusion. In some cases, the microfluidic channel 830 can be formed as or from one of the grooves or channels that can be formed in the aforementioned rectangular PC preform, which can then be used to create a mini-preform of the fiber probe structure 810 and ultimately the fiber probe structure 810. In other examples, the microfluidic channel 830 can be formed as or from a tube inserted in one of the grooves or channels that can be formed in the above-described rectangular PC preform that can be used to create a mini-preform of the fiber probe structure 810 and ultimately the fiber probe structure 810 as described herein. For instance, the microfluidic channel 830 can be formed as or from a PC tube having a 50 μm OD and a 25 μm inner diameter ID, although other OD and/or ID dimensions may be relied on in some cases. In one example, the cross-sectional area of the microfluidic channel 830 is uniform or approximately uniform throughout its length. The microfluidic channel 830 can have a diameter ranging between, for instance, approximately 5 μm to approximately 100 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, the microfluidic channel 830 of the probe device 800 can have a diameter of approximately 75 μm. [0159] The tetrodes 840 and the electrodes 842, 844, 846, 848 can be independently or collectively configured and operable to record extracellular voltage. In some cases, any or all of the electrodes 842, 844, 846, 848 can be formed using a bismuth tin (BiSn) alloy material, a nichrome (NiCr) alloy material, a stainless steel alloy material, a gold or gold alloy material, a platinum or platinum alloy material, a tungsten or tungsten alloy material, another material or alloy, or any combination thereof. In some examples, each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840 is formed using the same material or materials. In other examples, at least one of the electrodes 842, 844, 846, 848 of any of the tetrodes 840 may be formed using a material that is different from any material used to form at least one of the other electrodes 842, 844, 846, 848 in at Attorney Docket: 222204-2920 least one of the other tetrodes 840. In the example shown, a cross-sectional area of each of the tetrodes 840 at the first end of the fiber probe structure 810 equals a corresponding cross-sectional area of the tetrodes 840 at or proximate to the second end of the fiber probe structure 810. For instance, the size of a cross-sectional area of each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c at the first end of the fiber probe structure 810 is the same as or approximately the same as the size of a corresponding cross-sectional area of each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c at or proximate to the second end of the fiber probe structure 810. For example, the cross-sectional area of each of the tetrodes 840 (e.g., the cross-sectional area of each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c) is uniform or approximately uniform throughout its length. Any or all of the electrodes 842, 844, 846, 848 can have a diameter ranging between, for instance, approximately 5 μm to approximately 100 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, each of the electrodes 842, 844, 846, 848 of the probe device 800 can have a diameter of approximately 25 μm. [0160] The probe device 800 also includes a tip region 850 positioned at the first end (e.g., first distal end) of the fiber probe structure 810. The tip region 850 can include a tip that can be formed to various geometries (e.g., shapes or surface shapes), configurations (e.g., arrangements of probe components exposed at a surface of the tip), orientations (e.g., cut angles), and micro-scale dimensions (e.g., micro-scaled cross-sections of probe components exposed at a surface of the tip) as described in examples herein. In the example shown, the tip of the tip region 850 is embodied as an angled tip 855. Either or both of the tip region 850 and the angled tip 855 can be defined by and formed as a result of a crosscut of at least one of the fiber probe structure 810, the silica optical waveguide 820, the microfluidic channel 830, the tetrodes 840, or the electrodes 842, 844, 846, 848. For instance, the crosscut can be an angled crosscut that can be formed at a defined angle (^) relative to a cross-section of the tip region 850 or the longitudinal axis of the fiber probe structure 810. In the example shown, the angled tip 855 can be formed at such a defined angle (^) relative to a cross- section of the tip region 850 or the longitudinal axis of the fiber probe structure 810. [0161] In some examples, the tip of the tip region 850 may be embodied as a flat tip rather than an angled tip. In these examples, either or both of the tip region 850 and the tip of the tip region 850 can be defined by and formed as a result of a straight crosscut of at least one of the fiber probe structure 810, the optical waveguide 820, the microfluidic channel 830, or the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c). For instance, the tip region 850 can be crosscut at an angle that is normal to the longitudinal axis of the fiber probe structure 810. Attorney Docket: 222204-2920 In some cases, the tip of the tip region 850 may be embodied as a multi-angled tip having multiple outer (e.g., exposed) surfaces that have been crosscut at different cut angles relative to a cross-section of the tip region 850 or the longitudinal axis of the fiber probe structure 810. In these examples, one or more exposed surfaces of any or all of the fiber probe structure 810, the optical waveguide 820, the microfluidic channel 830, or the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c) may be formed to at least one of such different cut angles at the tip of the tip region 850. The tip region 850, the angled tip 855, or both can be formed to various defined dimensions such as, for instance, at least one of a defined width or a defined thickness. In the example shown, the tip region 850 and the angled tip 855 are formed to the width (w) of the fiber probe structure 810 ranging between approximately 50 μm to approximately 750 μm. In one embodiment, the tip region 850, the angled tip 855, or both can have a width of approximately 500 μm. In the example shown, the tip region 850 and the angled tip 855 are formed to the thickness (t) of the fiber probe structure 810 ranging between approximately 10 μm to approximately 250 μm. In one embodiment, the tip region 850, the angled tip 855, or both can have a thickness of approximately 100 μm. [0162] The probe device 800 further includes a backend connector region 860 positioned at or proximate to the second end (e.g., second distal end) of the fiber probe structure 810. The backend connector region 860 can be configured and operable to provide for coupling of one or more probe components of the fiber probe structure 810 to one or more devices that are external to and separate from the probe device 800. In the example shown, the backend connector region 860 can be configured and operable to provide for coupling of the silica optical waveguide 820, the microfluidic channel 830, and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840) to one or more devices that are external to and separate from the probe device 800. [0163] The backend connector region 860 includes a backend portion (e.g., an exposed backend portion) of the silica optical waveguide 820 extending from the second end of the fiber probe structure 810. The backend portion of the silica optical waveguide 820 can be configured and operable for coupling (e.g., optically, communicatively, operatively) to an external optical component or device such that a tip portion of the silica optical waveguide 820 at the first end of the fiber probe structure 810 can be coupled (e.g., optically, communicatively, operatively) to such an external optical component or device. For instance, the backend portion of the silica optical waveguide 820 can be configured and operable for coupling to an external optical component or device such that an exposed crosscut surface of the silica optical waveguide 820 at the angled tip 855 can be coupled to such an external optical component or device. Attorney Docket: 222204-2920 [0164] In some examples, the backend connector region 860 can further include an optic fiber coupled (e.g., optically, communicatively, operatively) to the backend portion of the silica optical waveguide 820 at or proximate to the second end of the fiber probe structure 810. In these examples, the optic fiber can be coupled to the backend portion of the silica optical waveguide 820 at or proximate to the second end of the fiber probe structure 810 such that a tip portion of the silica optical waveguide 820 at the first end of the fiber probe structure 810 can be coupled (e.g., optically, communicatively, operatively) to an external device. For instance, the optic fiber can be coupled to the backend portion of the silica optical waveguide 820 at or proximate to the second end of the fiber probe structure 810 such that an exposed crosscut surface of the silica optical waveguide 820 at the angled tip 855 can be coupled (e.g., optically, communicatively, operatively) to an external device. For example, the optic fiber can be directly coupled to the backend portion of the silica optical waveguide 820 at or proximate to the second end of the fiber probe structure 810. In some examples, the optic fiber can be embodied as or include at least one of a silicon or a silica material. In some cases, the optic fiber can be embodied as at least one of a silica optical fiber or cable or a silica-silica optical fiber or cable having a silica glass core and a silica glass cladding with a refractive index that is lower than that of the silica glass core. In one example, the optic fiber can have a diameter of 200 μm. In other examples, the backend connector region 860 can further include a fiber optic connector. In one example, the fiber optic connector can be embodied as a stainless steel fiber optic ferrule. For instance, the fiber optic connector can be embodied as a stainless steel fiber optic ferrule having an outer diameter of 1.25 mm. In one example, the fiber optic connector can be coupled to the backend portion of the silica optical waveguide 820 at or proximate to the second end of the fiber probe structure 810. [0165] The backend connector region 860 further includes a microfluidic tube 835 coupled (e.g., fluidly, operatively) to the microfluidic channel 830 at or proximate to the second end of the fiber probe structure 810. In various examples, the microfluidic tube 835 can be coupled to a backend portion of the microfluidic channel 830 at or proximate to the second end of the fiber probe structure 810 such that a tip portion of the microfluidic channel 830 at the first end of the fiber probe structure 810 can be coupled (e.g., fluidly, operatively) to an external device. For instance, the microfluidic tube 835 can be coupled to the backend portion of the microfluidic channel 830 at or proximate to the second end of the fiber probe structure 810 such that an opened crosscut portion of the microfluidic channel 830 at the angled tip 855 can be coupled (e.g., fluidly, operatively) to an external device. The microfluidic tube 835 in the example shown is at least partly inserted into the microfluidic channel 830 at the second end of the fiber probe structure 810. In one example, the Attorney Docket: 222204-2920 microfluidic tube 835 can be embodied as a polycarbonate (PC) tube. For instance, the microfluidic tube 835 can be embodied as a PC tube having a 150 μm OD and a 75 μm ID, although other OD and/or ID dimensions may be relied on in some cases. In other examples, the backend connector region 860 can further include a fluidic connector. In one example, the fluidic connector can be coupled to the microfluidic tube 835. [0166] The backend connector region 860 further includes backend portions (e.g., exposed backend portions) of the tetrodes 840 (e.g., exposed backend portions of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c) extending from the second end of the fiber probe structure 810. The backend portions of the tetrodes 840 (e.g., backend portions of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c) can be configured and operable for coupling (e.g., electrically, communicatively, operatively) to an external electrical component or device such that tip portions of the tetrodes 840 (e.g., tip portions of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c) at the first end of the fiber probe structure 810 can be coupled (e.g., electrically, communicatively, operatively) to such an external electrical component or device. For instance, the backend portions of the tetrodes 840 can be configured and operable for coupling to an external electrical component or device such that an exposed crosscut surface of each of the tetrodes 840 (e.g., an exposed crosscut surface of each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c) at the angled tip 855 can be coupled to such an external electrical component or device. [0167] In some examples, the backend connector region 860 can further include one or more electrical connectors respectively coupled to one or more of the tetrodes 840 (e.g., to the electrodes 842, 844, 846, 848 of one or more of the tetrodes 840) at or proximate to the second end of the fiber probe structure 810. In these examples, each of such electrical connectors can be coupled (e.g., electrically, communicatively, operatively) to the backend portion of a tetrode 840 (e.g., to backend portions of the electrodes 842, 844, 846, 848 of the tetrode 840) such that a tip portion of the tetrode 840 (e.g., tip portions of the electrodes 842, 844, 846, 848 of the tetrode 840) at the first end of the fiber probe structure 810 can be coupled (e.g., electrically, communicatively, operatively) to an external device. For instance, each of the electrical connectors can be coupled to a backend portion of each electrode 842, 844, 846, 848 of a tetrode 840 at or proximate to the second end of the fiber probe structure 810 such that an exposed crosscut surface of the tetrode 840 (e.g., an exposed crosscut surface of each electrode 842, 844, 846, 848 of the tetrode 840) at the angled tip 855 can be coupled to an external device. In these examples, each of such electrical connectors can be directly coupled to one of the tetrodes 840 (e.g., to the electrodes 842, 844, 846, 848 of a tetrode 840). Any or all of Attorney Docket: 222204-2920 such electrical connectors in these examples can be embodied as a wire such as, for example, a copper wire. In one example, any or all of the electrical connectors can be embodied as an insulated copper wire. In one example, any or all of the electrical connectors can be embodied as a 42AWG copper wire. In other examples, the backend connector region 860 can further include one or more pin connectors, a PCB, or any combination thereof. In one example, one end of each of the above- described electrical connectors can be coupled to the backend portion of a tetrode 840 (e.g., to an exposed backend portion of each electrode 842, 844, 846, 848 of the tetrode 840) at or proximate to the second end of the fiber probe structure 810 and another end of the electrical connector can be coupled to a pin connector. In another example, one end of each of the electrical connectors can be coupled to the backend portion of a tetrode 840 (e.g., to an exposed backend portion of each electrode 842, 844, 846, 848 of the tetrode 840) at or proximate to the second end of the fiber probe structure 810 and another end of the electrical connector can be coupled to a PCB. [0168] In some cases, the probe device 800 can further include a sealant to seal the microfluidic tube 835 to the microfluidic channel 830. For example, the probe device 800 can include a UV epoxy resin that can be coupled to the second end of the fiber probe structure 810 and further coupled to the microfluidic tube 835 and/or the aforementioned fluidic connector. In some cases, the UV epoxy resin can be further coupled to any or all of the backend portion of the silica optical waveguide 820, the aforementioned fiber optic connector or optic fiber, the backend portions of the tetrodes 840 (e.g., backend portions of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c), the aforementioned electrical connectors, pin connectors, or PCB, or any combination thereof, to provide support for such components. [0169] The probe device 800 can be fabricated according to various dimensions, geometries, configurations, or any combination thereof. In some cases, the probe device 800 can be fabricated such that the silica optical waveguide 820, the microfluidic channel 830, and/or the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848) are collocated within the fiber probe structure 810 according to different arrangements. For example, the probe device 800 can be fabricated such that the silica optical waveguide 820, the microfluidic channel 830, and/or the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848) are collocated within the fiber probe structure 810 according to either of the probe component arrangements 600a or 600b described herein and illustrated in FIGS. 6A and 6B, respectively, or according to another probe component arrangement. In examples where the probe device 800 is fabricated according to either of the probe component arrangements 600a, 600b, the silica optical waveguide 820 can be used in place of the optical waveguide 520 and the electrodes 842, 844, 846, 848 can be used in place of the electrodes 542, 544, 546, 548. Attorney Docket: 222204-2920 [0170] The fiber probe structure 810 of the probe device 800 can be fabricated according to either of the probe component arrangements 600a, 600b or another probe component arrangement by implementing the preform fabrication process 700a, the thermal drawing process 700b, and the thermal tapering process 700c described herein and illustrated in FIGS.7A, 7B, and 7C, respectively. The probe device 800 in its entirety can be fabricated by implementing the preform fabrication process 700a, the thermal drawing process 700b, the thermal tapering process 700c, and the backend connection process 700d described herein and illustrated in FIGS.7A, 7B, 7C and 7D, respectively. [0171] In examples where the thermal tapering process 700c is implemented to ultimately form the fiber probe structure 810, at 702c of the thermal tapering process 700c the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c) can be inserted into respective channels 730 of the mini-preform 709a in place of the optical waveguide 720 and the tetrodes 740 (e.g., the electrodes 742, 744, 746, 748 of each of the tetrodes 740a, 740b, 740c), respectively. In these examples, at 704c of the thermal tapering process 700c the mini-preform 709b having the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c) inserted therein can be heated and pulled in opposite directions as described herein. In these examples, the mini-preform 709b can be heated and pulled until the material (e.g., polymer or polycarbonate material) of the mini-preform 709b in the reduced cross-section region 750 fractures as a result of such heating and pulling. In these examples, the melting temperatures of the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c) can be significantly higher relative to the melting temperature of the material of the mini-preform 709b. As a result, upon fracturing of the material of the mini-preform 709b in the reduced cross-section region 750 during 704c of the thermal tapering process 700c, portions of the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c) located at or adjacent to the fracture point of the mini-preform 709b can be exposed and extend from the fractured end of the mini-preform 709b. In these examples, another location along the reduced cross- section region 750 created in the mini-preform 709b can be cut at 704c of the thermal tapering process 700c as described herein to produce the fiber probe structure 810. For instance, an end of the reduced cross-section region 750 that is opposite from the fractured end can be cut to form the tip region 850 of the fiber probe structure 810. For example, an end of the reduced cross-section region 750 that is opposite from the fractured end can be cut with the crosscut 711 at a defined angle (^) to form the angled tip 855 of the fiber probe structure 810. In this example, the portions of the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of the tetrodes 840a, Attorney Docket: 222204-2920 840b, 840c) located at or adjacent to the fracture point of the mini-preform 709b can also be cut to create the backend connector region 860, at least partly. [0172] FIGS.9A and 9B illustrate views of another example multi-modal fiber probe device 900 (or “probe device 900”) according to various aspects and embodiments of the present disclosure. FIG.9A illustrates a top view of the example multi-modal fiber probe device 900 according to various aspects and embodiments of the present disclosure. FIG. 9B illustrates a front view of a tip region 950 of the example multi-modal fiber probe device 900 according to various aspects and embodiments of the present disclosure. The probe device 900 can be designed, embodied, and implemented as a multi-modal neural fiber probe device in examples herein. For instance, the probe device 900 can be designed, embodied, and implemented as a fiber Photometry, Drug delivery, Optical stimulation, and Electrophysiology (P-DOpE) probe device described in various embodiments herein. Similar to the probe devices 100, 500, and 800, the probe device 900 offers relatively higher complexities at a tip region compared to existing devices while also easing the connection between a backend connector region and external electronics that may be coupled to the probe device 900. Additionally, the probe device 900 can be implemented to concurrently (e.g., simultaneously) perform various electrophysiology and fiber photometry operations in a subject (e.g., a patient, person, animal). For instance, the probe device 900 can be implemented to perform simultaneous electrophysiology and fiber photometry in such a subject, thereby allowing for the cross-referencing of electrical and optical signals in the subject. The probe device 900 can be designed and embodied as a fiber P-DOpE probe device described herein that has a relatively high spatial and temporal resolution and is capable of detecting both electrical and chemical signals. [0173] The probe device 900 is an example alternative embodiment of the probe device 800 described herein and illustrated in FIGS. 8A to 8C. The probe device 900 can include the same or similar structure, components, features, materials, and functionality as that of the probe device 800. A difference between the probe device 900 and the probe device 800 is that the cross-sectional geometry of the probe device 900 is circular, as opposed to rectangular. Another difference between the probe device 900 and the probe device 800 is that the tip region 950 of the probe device 900 includes a flat tip, as opposed to an angled tip. Another difference between the probe device 900 and the probe device 800 is the arrangement of optical waveguides, microfluidic channels, and tetrodes relative to one another in each of such devices. Another difference between the probe device 900 and the probe device 100 is the number of tetrodes in each of such devices. [0174] The probe device 900 illustrated in FIGS. 9A and 9B includes a fiber probe structure 910. The fiber probe structure 910 can include one or more of the optical waveguides 820, one or Attorney Docket: 222204-2920 more of the microfluidic channels 830, one or more of the tetrodes 840, or any combination thereof. In the example shown, the fiber probe structure 910 includes a single silica optical waveguide 820, a single microfluidic channel 830, and seven tetrodes 840a, 840b, 840c, 840d, 540e, 840f, 840g. In this example, each of the tetrodes 840 is embodied as and thus includes electrodes 842, 844, 846, 848. For instance, the tetrode 840a is embodied as and includes electrodes 842a, 844a, 846a, 848a, the tetrode 840b is embodied as and includes electrodes 842b, 844b, 846b, 848b, the tetrode 840c is embodied as and includes electrodes 842c, 844c, 846c, 848c, the tetrode 840d is embodied as and includes electrodes 842d, 844d, 846d, 848d, the tetrode 840e is embodied as and includes electrodes 842e, 844e, 846e, 848e, the tetrode 840f is embodied as and includes electrodes 842f, 844f, 846f, 848f, and the tetrode 840g is embodied as and includes electrodes 842g, 844g, 846g, 848g. Only the tetrodes 840c, 840f and their respective electrodes 846, 848 are denoted in FIG.9A for clarity. Only certain tetrodes 840 and their respective electrodes 842, 844, 846, 848 are denoted in FIG. 9B for clarity. The silica optical waveguide 820, the microfluidic channel 830, and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848) can be formed in the fiber probe structure 910 such that they are collocated about and extend along a longitudinal axis of the fiber probe structure 910 from a first end (e.g., a first distal end) to a second end (e.g., a second distal end) of the fiber probe structure 910 as illustrated collectively across FIGS. 9A and 9B. For instance, the silica optical waveguide 820, the microfluidic channel 830, and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) can be formed in the fiber probe structure 910 such that they are positioned at the same radial distance or different radial distances from a longitudinal axis (e.g., a center) of the fiber probe structure 910. The longitudinal axis of the fiber probe structure 910 in this example is located at a center of the silica optical waveguide 820 and it extends into and out of the page of FIG.9B in a direction that is parallel to an axis “Z.” [0175] In the example shown, the fiber probe structure 910 is embodied with a cylindrical shape and circular cross-section. In various embodiments, a cross-section of the first end of the fiber probe structure 910 and a corresponding cross-section of the second end of the fiber probe structure 910 are each embodied as a circular-shaped cross-section. For instance, a cross-section taken at or proximate to the first end of the fiber probe structure 910 that is normal to the longitudinal axis of the fiber probe structure 910 and a corresponding cross-section taken at or proximate to the second end of the fiber probe structure 910 that is also normal to the longitudinal axis of the fiber probe structure 910 are both circular-shaped cross-sections in the example shown. Although the fiber probe structure 910 illustrated in FIGS.9A and 9B is embodied with a cylindrical shape and circular cross- section, the scope of the present disclosure is not so limited. In other examples the fiber probe Attorney Docket: 222204-2920 structure 910 may be embodied such that it has a rectangular-shaped cross-section, an annular-shaped cross-section, a triangular-shaped cross-section, a square-shaped cross-section, or a cross-section having another geometry. In some embodiments, a cross-section of the first end of the fiber probe structure 910 and a corresponding cross-section of the second end of the fiber probe structure 910 are each embodied as a rectangular-shaped cross-section, a square-shaped cross-section, a triangular- shaped cross-section, or a cross-section having another geometry. [0176] The fiber probe structure 910 includes an annular region 911 having an annular-shaped cross-section. The annular region 911 in this example surrounds the silica optical waveguide 820 and extends from the first end to the second end of the fiber probe structure 910. For instance, the annular region 911 surrounds the silica optical waveguide 820 and extends into and out of the page of FIG. 9B from the first end to the second end of the fiber probe structure 910 in a direction that is parallel to the “Z” axis. In the probe component arrangement shown in FIGS. 9A and 9B, the microfluidic channel 830 and each of the tetrodes 840 (e.g., each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) is positioned in and extends through the annular region 911 from the first end to the second end of the fiber probe structure 910. For instance, the microfluidic channel 830 and each of the tetrodes 840 (e.g., each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) is positioned in the annular region 911 and extends into and out of the page of FIG. 9B from the first end to the second end of the fiber probe structure 910 in a direction that is parallel to the “Z” axis. [0177] The fiber probe structure 910 can further include one or more divider regions positioned between at least two of any of the silica optical waveguide 820, the microfluidic channel 830, or the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g). Only certain divider regions of the fiber probe structure 910 are described herein for brevity and denoted in FIGS. 9A and 9B for clarity. The divider regions can extend along an entire length of the fiber probe structure 910, and they can isolate (e.g., physically) and insulate (e.g., electrically, optically, electromagnetically, chemically) such probe components from one another. [0178] In the example shown, the fiber probe structure 910 includes a divider region 915a positioned in the annular region 911 between the silica optical waveguide 820 and each of the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g). The divider region 915a in this example surrounds the silica optical waveguide 820 and extends from the first end to the second end of the fiber probe structure 910. For instance, the divider region 915a surrounds the silica optical waveguide 820 and extends into and out of the page of FIG. 9B from the first end to the second end of the fiber probe structure 910 in a direction that is parallel Attorney Docket: 222204-2920 to the “Z” axis. The divider region 915a isolates (e.g., physically) and insulates (e.g., electrically, optically, electromagnetically, chemically) the silica optical waveguide 820 from the tetrodes 840 (e.g., from the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) and vice versa. The divider region 915a includes material from one or more portions of at least one of the fiber probe structure 910 (e.g., polymer or polycarbonate used to form the fiber probe structure 910), the silica optical waveguide 820 (e.g., a cladding surrounding the silica optical waveguide 820 and/or a coating, wrap, sheath, or jacket surrounding the cladding), the microfluidic channel 830 (e.g., polymer or polycarbonate tube used to form the microfluidic channel 830), or the tetrodes 840 (e.g., an insulating coating, wrap, sheath, or jacket of one or more of the electrodes 842, 844, 846, 848 of any or all of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g). [0179] In the example shown, the fiber probe structure 910 further includes divider regions positioned in the annular region 911 between the microfluidic channel 830 and the tetrodes 840d, 840e (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840d, 840e). For example, the fiber probe structure 910 includes a divider region 915b positioned in the annular region 911 between the microfluidic channel 830 and the tetrode 840e (e.g., the electrodes 842e, 848e of the tetrode 840e). The divider region 915b in this example is located between such probe components and it extends from the first end to the second end of the fiber probe structure 910. For instance, the divider region 915b extends into and out of the page of FIG. 9B from the first end to the second end of the fiber probe structure 910 in a direction that is parallel to the “Z” axis. The divider region 915b isolates (e.g., physically) and insulates (e.g., electrically, optically, electromagnetically, chemically) any or all of the electrodes 842, 844, 846, 848 of the tetrodes 840e from the microfluidic channel 830. The divider region 915b includes material from one or more portions of at least one of the fiber probe structure 910 (e.g., polymer or polycarbonate used to form the fiber probe structure 910), the microfluidic channel 830 (e.g., polymer or polycarbonate tubes used to at least partly form the microfluidic channel 830), or the tetrode 840e (e.g., an insulating coating, wrap, sheath, or jacket of one or both of the electrodes 842e, 848e). The fiber probe structure 910 in this example further includes additional divider regions positioned in the annular region 911 between pairs of the tetrodes 840 (e.g., between the electrodes 842, 844, 846, 848 of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g). These additional divider regions isolate (e.g., physically) and insulate (e.g., electrically, electromagnetically) pairs of the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) from one another. The additional divider regions include material from one or more portions of at least one of the fiber probe structure 910 (e.g., polymer or polycarbonate used to form the fiber probe structure 910) or the tetrodes 840 (e.g., an insulating Attorney Docket: 222204-2920 coating, wrap, sheath, or jacket of any or all of the electrodes 842, 844, 846, 848 of any or all of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g). [0180] The fiber probe structure 910 can be formed using and can thus include one or more preform materials used to fabricate fiber probe structures such as, for instance, at least one of a polymer material or a polycarbonate (PC) material. In some examples, the fiber probe structure 910 can be formed using a polymer or polycarbonate rod having grooves or channels in which optical waveguides and tetrodes (e.g., electrodes of each tetrode) can be inserted, and in which microfluidic channels can be formed as described in examples herein. In some cases, one or more polymer or polycarbonate films can be wrapped around such a polymer or polycarbonate rod, as well as the optical waveguides, microfluidic channels, and tetrodes (e.g., electrodes of each tetrode) positioned in the rod to form a preform of the fiber probe structure 910. Such a preform can then be processed into a mini-preform that can be used to create the tapered fiber probe structure 110 as described further in examples herein. [0181] The silica optical waveguide 820 can be configured and operable to control optogenetics in the same or similar manner in each of the probe devices 800, 900. The silica optical waveguide 820 can also be embodied in the same or similar manner in each of the probe devices 800, 900. In some cases, the silica optical waveguide 820 can be embodied to include the same material and with the same dimensions in each of the probe devices 800, 900. In other examples, the silica optical waveguide 820 can be embodied with one or more materials or dimensions that are different in each of the probe devices 800, 900. In some examples, the silica optical waveguide 820 can be embodied as or include at least one of a silicon or a silica material. In some cases, the silica optical waveguide 820 can be embodied as at least one of a silica optical fiber waveguide, a silica fiber, a silica-silica fiber, or another silica-based optical fiber. For instance, the silica optical waveguide 820 can be embodied as or include a silica optical fiber having a silica glass core and a silica glass cladding with a refractive index that is lower than that of the silica glass core. In the example shown, a cross- sectional area of the silica optical waveguide 820 at the first end of the fiber probe structure 910 equals a corresponding cross-sectional area of the optical waveguide 820 at or proximate to the second end of the fiber probe structure 910. For instance, the size of a cross-sectional area of the silica optical waveguide 820 at the first end of the fiber probe structure 910 is the same as or approximately the same as the size of a corresponding cross-sectional area of the optical waveguide 820 at or proximate to the second end of the fiber probe structure 910. For example, the cross- sectional area of the silica optical waveguide 820 is uniform or approximately uniform throughout its length. The silica optical waveguide 820 can have a diameter ranging between, for instance, Attorney Docket: 222204-2920 approximately 70 μm to approximately 300 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, the silica optical waveguide 820 of the probe device 900 can have a diameter of approximately 200 μm. [0182] The microfluidic channel 830 can be configured and operable to allow for focal drug infusion in the same or similar manner in each of the probe devices 800, 900. The microfluidic channel 830 can also be embodied in the same or similar manner in each of the probe devices 800, 900. In some cases, the microfluidic channel 830 can be embodied to include the same material (e.g., a PC tube) and to the same dimensions in each of the probe devices 800, 900. In other examples, the microfluidic channel 830 can be embodied with one or more materials or dimensions that are different in each of the probe devices 800, 900. In some cases, the microfluidic channel 830 can be formed as or from one of the grooves or channels that can be formed in the aforementioned PC rod, which can then be used to create a mini-preform of the fiber probe structure 910 and ultimately the fiber probe structure 910. In other examples, the microfluidic channel 830 can be formed as or from a tube inserted in one of the grooves or channels that can be formed in the above-described PC rod that can be used to create a mini-preform of the fiber probe structure 910 and ultimately the fiber probe structure 910 as described herein. For instance, the microfluidic channel 830 can be formed as or from a PC tube having a 50 μm OD and a 25 μm inner diameter ID, although other OD and/or ID dimensions may be relied on in some cases. In one example, the cross-sectional area of the microfluidic channel 830 is uniform or approximately uniform throughout its length. The microfluidic channel 830 can have a diameter ranging between, for instance, approximately 5 μm to approximately 100 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, the microfluidic channel 830 of the probe device 900 can have a diameter of approximately 75 μm. [0183] The tetrodes 840 and the electrodes 842, 844, 846, 848 can be independently or collectively configured and operable to record extracellular voltage in the same or similar manner in each of the probe devices 800, 900. The tetrodes 840 can also be embodied in the same or similar manner in each of the probe devices 800, 900. In some cases, each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g can be embodied to include the same material and to the same dimensions in each of the probe devices 800, 900. In other examples, at least one of the electrodes 842, 844, 846, 848 of one or more of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g can be embodied with a material or dimension that is different from that of at least one of the other electrodes 842, 844, 846, 848 of at least one the other tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g. In some cases, any or all of the electrodes 842, 844, 846, 848 can be Attorney Docket: 222204-2920 formed using a bismuth tin (BiSn) alloy material, a nichrome (NiCr) alloy material, a stainless steel alloy material, a gold or gold alloy material, a platinum or platinum alloy material, a tungsten or tungsten alloy material, another material or alloy, or any combination thereof. In some examples, each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g is formed using the same material or materials. In other examples, at least one of the electrodes 842, 844, 846, 848 of any of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g may be formed using a material that is different from any material used to form at least one of the other electrodes 842, 844, 846, 848 in at least one of the other tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g. In the example shown, a cross-sectional area of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g at the first end of the fiber probe structure 910 equals a corresponding cross-sectional area of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g at or proximate to the second end of the fiber probe structure 910. For instance, the size of a cross-sectional area of each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g at the first end of the fiber probe structure 910 is the same as or approximately the same as the size of a corresponding cross- sectional area of each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g at or proximate to the second end of the fiber probe structure 910. For example, the cross-sectional area of each of the tetrodes 840 (e.g., the cross-sectional area of each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) is uniform or approximately uniform throughout its length. Any or all of the electrodes 842, 844, 846, 848 can have a diameter ranging between, for instance, approximately 5 μm to approximately 100 μm, although another diameter outside this range may be relied upon in some cases. In the example shown, each of the electrodes 842, 844, 846, 848 of the probe device 900 can have a diameter of approximately 25 μm. [0184] The probe device 900 also includes a tip region 950 positioned at the first end (e.g., first distal end) of the fiber probe structure 910. The tip region 950 can include a tip that can be formed to various geometries (e.g., shapes or surface shapes), configurations (e.g., arrangements of probe components exposed at a surface of the tip), orientations (e.g., cut angles), and micro-scale dimensions (e.g., micro-scaled cross-sections of probe components exposed at a surface of the tip) as described in examples herein. In the example shown, the tip of the tip region 950 is embodied as a flat tip 955. Either or both of the tip region 950 and the flat tip 955 can be defined by and formed as a result of a crosscut of at least one of the fiber probe structure 910, the silica optical waveguide 820, the microfluidic channel 830, the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g, or the electrodes 842, 844, 846, 848. For instance, either or both of the tip region 950 and the flat tip region Attorney Docket: 222204-2920 955 can be defined by and formed as a result of a straight crosscut of at least one of the fiber probe structure 910, the optical waveguide 820, the microfluidic channel 830, or the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g). For example, the tip region 950 can be crosscut at an angle that is normal to the longitudinal axis of the fiber probe structure 910 to form the flat tip 955. [0185] In some examples, the tip of the tip region 950 may be embodied as an angled tip rather than a flat tip. In these examples, either or both of the tip region 950 and the angled tip can be defined by and formed as a result of an angled crosscut that can be formed at a defined angle (^) relative to a cross-section of the tip region 950 or the longitudinal axis of the fiber probe structure 910. In some cases, the tip of the tip region 950 may be embodied as a multi-angled tip having multiple outer (e.g., exposed) surfaces that have been crosscut at different cut angles relative to a cross-section of the tip region 950 or the longitudinal axis of the fiber probe structure 910. In these examples, one or more exposed surfaces of any or all of the fiber probe structure 910, the optical waveguide 820, the microfluidic channel 830, or the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) may be formed to at least one of such different cut angles at the tip of the tip region 950. The tip region 950, the flat tip 955, or both can be formed to various defined dimensions such as, for instance, a defined diameter (D). In one example, the tip region 950, the flat tip 955, or both can be formed to a diameter of approximately 50 μm. In another example, the tip region 950, the flat tip 955, or both can be formed to a diameter ranging between 50 μm to 750 μm. In another example, the tip region 950, the flat tip 955, or both can be formed to a diameter of approximately 750 μm. In some cases, the tip region 950, the flat tip 955, or both can be formed to a diameter that is less than 50 μm or greater than 750 μm. [0186] The probe device 900 further includes a backend connector region 960 positioned at or proximate to the second end (e.g., second distal end) of the fiber probe structure 910. The backend connector region 960 can be configured and operable to provide for coupling of one or more probe components of the fiber probe structure 910 to one or more devices that are external to and separate from the probe device 900. In the example shown, the backend connector region 960 can be configured and operable to provide for coupling of the silica optical waveguide 820, the microfluidic channel 830, and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840) to one or more devices that are external to and separate from the probe device 900. [0187] The backend connector region 960 includes a backend portion (e.g., an exposed backend portion) of the silica optical waveguide 820 extending from the second end of the fiber probe structure 910. The backend portion of the silica optical waveguide 820 can be configured and operable for Attorney Docket: 222204-2920 coupling (e.g., optically, communicatively, operatively) to an external optical component or device such that a tip portion of the silica optical waveguide 820 at the first end of the fiber probe structure 910 can be coupled (e.g., optically, communicatively, operatively) to such an external optical component or device. For instance, the backend portion of the silica optical waveguide 820 can be configured and operable for coupling to an external optical component or device such that an exposed crosscut surface of the silica optical waveguide 820 at the flat tip 955 can be coupled to such an external optical component or device. [0188] In some examples, the backend connector region 960 can further include an optic fiber coupled (e.g., optically, communicatively, operatively) to the backend portion of the silica optical waveguide 820 at or proximate to the second end of the fiber probe structure 910. In these examples, the optic fiber can be coupled to the backend portion of the silica optical waveguide 820 at or proximate to the second end of the fiber probe structure 910 such that a tip portion of the silica optical waveguide 820 at the first end of the fiber probe structure 910 can be coupled (e.g., optically, communicatively, operatively) to an external device. For instance, the optic fiber can be coupled to the backend portion of the silica optical waveguide 820 at or proximate to the second end of the fiber probe structure 910 such that an exposed crosscut surface of the silica optical waveguide 820 at the flat tip 955 can be coupled (e.g., optically, communicatively, operatively) to an external device. For example, the optic fiber can be directly coupled to the backend portion of the silica optical waveguide 820 at or proximate to the second end of the fiber probe structure 910. In some examples, the optic fiber can be embodied as or include at least one of a silicon or a silica material. In some cases, the optic fiber can be embodied as at least one of a silica optical fiber or cable or a silica-silica optical fiber or cable having a silica glass core and a silica glass cladding with a refractive index that is lower than that of the silica glass core. In one example, the optic fiber can have a diameter of 200 μm. In other examples, the backend connector region 960 can further include a fiber optic connector. In one example, the fiber optic connector can be embodied as a stainless steel fiber optic ferrule. For instance, the fiber optic connector can be embodied as a stainless steel fiber optic ferrule having an outer diameter of 1.25 mm. In one example, the fiber optic connector can be coupled to the backend portion of the silica optical waveguide 820 at or proximate to the second end of the fiber probe structure 910. [0189] The backend connector region 960 further includes the microfluidic tube 835 coupled (e.g., fluidly, operatively) to the microfluidic channel 830 at or proximate to the second end of the fiber probe structure 910. In various examples, the microfluidic tube 835 can be coupled to a backend portion of the microfluidic channel 830 at or proximate to the second end of the fiber probe structure Attorney Docket: 222204-2920 910 such that a tip portion of the microfluidic channel 830 at the first end of the fiber probe structure 910 can be coupled (e.g., fluidly, operatively) to an external device. For instance, the microfluidic tube 835 can be coupled to the backend portion of the microfluidic channel 830 at or proximate to the second end of the fiber probe structure 910 such that an opened crosscut portion of the microfluidic channel 830 at the flat tip 955 can be coupled (e.g., fluidly, operatively) to an external device. The microfluidic tube 835 in the example shown is at least partly inserted into the microfluidic channel 830 at the second end of the fiber probe structure 910. In one example, the microfluidic tube 835 can be embodied as a PC tube having a 50 μm OD and a 25 μm ID, although other OD and/or ID dimensions may be relied on in some cases. In other examples, the backend connector region 960 can further include a fluidic connector. In one example, the fluidic connector can be coupled to the microfluidic tube 835. [0190] The backend connector region 960 further includes backend portions (e.g., exposed backend portions) of the tetrodes 840 (e.g., exposed backend portions of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) extending from the second end of the fiber probe structure 910. The backend portions of the tetrodes 840 (e.g., backend portions of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) can be configured and operable for coupling (e.g., electrically, communicatively, operatively) to an external electrical component or device such that tip portions of the tetrodes 840 (e.g., tip portions of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) at the first end of the fiber probe structure 910 can be coupled (e.g., electrically, communicatively, operatively) to such an external electrical component or device. For instance, the backend portions of the tetrodes 840 can be configured and operable for coupling to an external electrical component or device such that an exposed crosscut surface of each of the tetrodes 840 (e.g., an exposed crosscut surface of each of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) at the flat tip 955 can be coupled to such an external electrical component or device. [0191] In some examples, the backend connector region 960 can further include one or more electrical connectors respectively coupled to one or more of the tetrodes 840 (e.g., to the electrodes 842, 844, 846, 848 of one or more of the tetrodes 840) at or proximate to the second end of the fiber probe structure 910. In these examples, each of such electrical connectors can be coupled (e.g., electrically, communicatively, operatively) to the backend portion of a tetrode 840 (e.g., to backend portions of the electrodes 842, 844, 846, 848 of the tetrode 840) such that a tip portion of the tetrode 840 (e.g., tip portions of the electrodes 842, 844, 846, 848 of the tetrode 840) at the first end of the fiber probe structure 910 can be coupled (e.g., electrically, communicatively, operatively) to an Attorney Docket: 222204-2920 external device. For instance, each of the electrical connectors can be coupled to a backend portion of each electrode 842, 844, 846, 848 of a tetrode 840 at or proximate to the second end of the fiber probe structure 910 such that an exposed crosscut surface of the tetrode 840 (e.g., an exposed crosscut surface of each electrode 842, 844, 846, 848 of the tetrode 840) at the flat tip 955 can be coupled to an external device. In these examples, each of such electrical connectors can be directly coupled to one of the tetrodes 840 (e.g., to the electrodes 842, 844, 846, 848 of a tetrode 840). Any or all of such electrical connectors in these examples can be embodied as a wire such as, for example, a copper wire. In one example, any or all of the electrical connectors can be embodied as an insulated copper wire. In one example, any or all of the electrical connectors can be embodied as a 42AWG copper wire. In other examples, the backend connector region 960 can further include one or more pin connectors, a PCB, or any combination thereof. In one example, one end of each of the above- described electrical connectors can be coupled to the backend portion of a tetrode 840 (e.g., to an exposed backend portion of each electrode 842, 844, 846, 848 of the tetrode 840) at or proximate to the second end of the fiber probe structure 910 and another end of the electrical connector can be coupled to a pin connector. In another example, one end of each of the electrical connectors can be coupled to the backend portion of a tetrode 840 (e.g., to an exposed backend portion of each electrode 842, 844, 846, 848 of the tetrode 840) at or proximate to the second end of the fiber probe structure 910 and another end of the electrical connector can be coupled to a PCB. [0192] In some cases, the probe device 900 can further include a sealant to seal the microfluidic tube 835 to the microfluidic channel 830. For example, the probe device 900 can include a UV epoxy resin that can be coupled to the second end of the fiber probe structure 910 and further coupled to the microfluidic tube 835 and/or the aforementioned fluidic connector. In some cases, the UV epoxy resin can be further coupled to any or all of the backend portion of the silica optical waveguide 820, the aforementioned fiber optic connector or optic fiber, the backend portions of the tetrodes 840 (e.g., backend portions of the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g), the aforementioned electrical connectors, pin connectors, or PCB, or any combination thereof, to provide support for such components. [0193] The probe device 900 can be fabricated according to various dimensions, geometries, configurations, or any combination thereof. In some cases, the probe device 900 can be fabricated such that the silica optical waveguide 820, the microfluidic channel 830, and/or the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848) are collocated within the fiber probe structure 910 according to different arrangements. For example, the probe device 900 can be fabricated such that the silica optical waveguide 820, the microfluidic channel 830, and/or the tetrodes 840 (e.g., the electrodes Attorney Docket: 222204-2920 842, 844, 846, 848) are collocated within the fiber probe structure 910 according to the probe component arrangement illustrated in FIG. 9B, or according to another probe component arrangement. [0194] The fiber probe structure 910 of the probe device 900 and the fiber probe structure 810 of the probe device 800 can each be fabricated according to various probe component arrangements in the same or similar manner. For example, the fiber probe structure 910 of the probe device 900 can be fabricated according to the probe component arrangement illustrated in FIG. 9B or another probe component arrangement by implementing the preform fabrication process 700a, the thermal drawing process 700b, and the thermal tapering process 700c in the same or similar manner as described herein with reference to fabrication of the fiber probe structure 810 of FIGS. 8A and 8B. In another example, the probe device 900 in its entirety can be fabricated by implementing the preform fabrication process 700a, the thermal drawing process 700b, the thermal tapering process 700c, and the backend connection process 700d described herein with reference to fabrication of the fiber probe structure 810 of FIGS.8A and 8B. [0195] In examples where the preform fabrication process 700a is implemented to ultimately form the fiber probe structure 910, multiple channels 730 can be formed through a polymer or PC rod (e.g., rather than a plate(s)) according to the probe component arrangement of the probe device 900 illustrated in FIGS. 9A and 9B to form a cylindrical preform. In examples where the thermal drawing process 700b is implemented to ultimately form the fiber probe structure 910, the cylindrical preform resulting from the preform fabrication process 700a can be drawn down to a cylindrical mini- preform having channels 730 that correspond to the probe component arrangement of the probe device 900. [0196] In examples where the thermal tapering process 700c is implemented to ultimately form the fiber probe structure 910, at 702c of the thermal tapering process 700c the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) can be inserted into respective channels 730 of the aforementioned cylindrical mini-preform resulting from the thermal drawing process 700b. In these examples the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) can be inserted into respective channels 730 of the cylindrical mini-preform in place of the optical waveguide 720 and the tetrodes 740 (e.g., the electrodes 742, 744, 746, 748 of each of the tetrodes 740a, 740b, 740c), respectively. In these examples, at 704c of the thermal tapering process 700c the cylindrical mini-preform having the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each Attorney Docket: 222204-2920 of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) inserted therein can be heated and pulled in opposite directions as described herein. In these examples, the cylindrical mini-preform can be heated and pulled until the material (e.g., polymer or polycarbonate material) of the cylindrical mini- preform in the reduced cross-section region 750 fractures as a result of such heating and pulling. In these examples, the melting temperatures of the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) can be significantly higher relative to the melting temperature of the material of the cylindrical mini-preform. As a result, upon fracturing of the material of the cylindrical mini-preform in the reduced cross-section region 750 during 704c of the thermal tapering process 700c, portions of the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of each of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) located at or adjacent to the fracture point of the cylindrical mini-preform can be exposed and extend from the fractured end of the cylindrical mini-preform. In these examples, another location along the reduced cross-section region 750 created in the cylindrical mini-preform can be cut at 704c of the thermal tapering process 700c as described herein to produce the fiber probe structure 910. For instance, an end of the reduced cross-section region 750 that is opposite from the fractured end can be cut to form the tip region 950 of the fiber probe structure 910. For example, an end of the reduced cross-section region 750 that is opposite from the fractured end can be cut with a straight crosscut to form the flat tip 955 of the fiber probe structure 910. In this example, the portions of the silica optical waveguide 820 and the tetrodes 840 (e.g., the electrodes 842, 844, 846, 848 of the tetrodes 840a, 840b, 840c, 840d, 840e, 840f, 840g) located at or adjacent to the fracture point of the cylindrical mini-preform can also be cut to create the backend connector region 960, at least partly. [0197] FIG.10 illustrates an example fabricated multi-modal fiber probe device 1000 (or “probe device 1000”) according to various aspects and embodiments of the present disclosure. In the example shown, the probe device 1000 includes a tapered fiber probe structure 1010 having a tip region 1050 with an angled tip 1055. In this example, the probe device 1000 is a fabricated embodiment of the probe device 100 described herein and illustrated in FIG.1. In this example, the tapered fiber probe structure 1010, the tip region 1050, and the angled tip 1055 are fabricated embodiments of the tapered fiber probe structure 110, the tip region 150, and the angled tip 155, respectively, of the probe device 100. [0198] FIG.11A illustrates an example implementation of the probe device 1000 of FIG. 10 in a straight position according to various aspects and embodiments of the present disclosure. For instance, FIG. 11A illustrates an example implementation of the tapered fiber probe structure 1010 Attorney Docket: 222204-2920 of the probe device 1000 in a straight position. FIG. 11B illustrates an example implementation of the probe device 1000 of FIG. 10 in a bent position according to various aspects and embodiments of the present disclosure. For instance, FIG.11B illustrates an example implementation of the tapered fiber probe structure 1010 of the probe device 1000 in a bent position. The illustrations depicted in FIGS.11A and 11B demonstrate the flexibility of the probe device 1000, for instance, the flexibility of the tapered fiber probe structure 1010. Several of the multi-modal fiber probe devices described herein and their respective fiber probe structures can achieve the same or similar flexibility as that of the probe device 1000 illustrated in FIGS. 11A and 11B. For example, a fabricated implementation of any of the probe devices 100, 500, or 800 can achieve the same or similar flexibility as that of the probe device 1000. In one example, a fabricated implementation of any of the probe devices 100, 500, 800, or 1000 can be bent to approximately a 45° angle without damaging or compromising the functionality or integrity of such a probe device. For instance, a fabricated implementation of any of the tapered fiber probe structure 110, the tapered fiber probe structure 510, the fiber probe structure 810, or the tapered fiber probe structure 1010 can be bent to approximately a 45° angle without damaging or compromising the functionality or integrity of such a fiber probe structure. [0199] FIG.12A illustrates another example implementation of the probe device 1000 according to various aspects and embodiments of the present disclosure. For instance, FIG. 12A illustrates an example implementation of the probe device 1000 with one or more optic fibers 1025, fiber optic connectors 1026, microfluidic tubes 1035, and connector electrodes 1045 (e.g., wires, pin connectors) coupled to a backend connector region 1060 of the probe device 1000 at least in part by way of an ultraviolet (UV) epoxy resin 1070. In this example, the probe device 1000 is a fabricated embodiment of the probe device 100 described herein and illustrated in FIG.1. In this example, the tapered fiber probe structure 1010, the tip region 1050, and the angled tip 1055 are fabricated embodiments of the tapered fiber probe structure 110, the tip region 150, and the angled tip 155, respectively, of the probe device 100. In this example, the optic fibers 1025, the microfluidic tubes 1035, the connector electrodes 1045, and the backend connector region 1060 are embodiments of the optic fibers 125, the microfluidic tubes 135, the connector electrodes 145, and the backend connector region 1060, respectively, of the probe device 100. In this example, the fiber optic connectors 1026 are embodiments of the fiber optic connectors described herein such as, for instance, stainless steel fiber optic ferrules. In this example, the UV epoxy resin 1070 is an embodiment of the UV epoxy resin described herein. [0200] FIG. 12A illustrates an example of a fully connected multi-modal fiber probe device according to at least one embodiment described herein. The probe device 1000 of FIG. 12A can Attorney Docket: 222204-2920 include eight electrodes (e.g., the electrodes 140) respectively coupled to eight connector electrodes 1045, eight microfluidic channels (e.g., the microfluidic channels 130) respectively coupled to eight microfluidic tubes 1035, and four optical waveguides (e.g., the optical waveguides 120) respectively coupled to four fiber optic connectors 1026 and/or four optic fibers 1025. The probe device 1000 of FIG. 12A can include the same attributes, structure, components, and functionality as that of the probe device 100 described herein and illustrated in FIG.1. The probe device 1000 of FIG.12A can be fabricated by implementing the preform fabrication process 400a, the thermal drawing process 400b, the thermal tapering process 400c, and the backend connection process 400d described herein and illustrated in FIGS.4A, 4B, 4C, and 4A, respectively. [0201] FIG.12B illustrates another example implementation of the probe device 1000 according to various aspects and embodiments of the present disclosure. For instance, FIG. 12B illustrates an example implementation of the probe device 1000 fabricated according to the probe component arrangement 200a described herein and illustrated in FIG. 2A. For example, FIG. 12B illustrates an example implementation of the probe device 1000 with one fiber optic connector 1026, one microfluidic tube 1035, and a printed circuit board (PCB) 1046 coupled to the backend connector region 1060 of the probe device 1000 at least in part by way of the UV epoxy resin 1070. In this example, the probe device 1000 is a fabricated embodiment of the probe device 100 described herein and illustrated in FIG. 1 and fabricated according to the probe component arrangement 200a described herein and illustrated in FIG. 2A. In this example, the tapered fiber probe structure 1010, the tip region 1050, and the angled tip 1055 are fabricated embodiments of the tapered fiber probe structure 110, the tip region 150, and the angled tip 155, respectively, of the probe device 100 fabricated according to the probe component arrangement 200a. In this example, the microfluidic tube 1035 and the backend connector region 1060 are embodiments of one of the microfluidic tubes 135 and the backend connector region 1060, respectively, of the probe device 100 fabricated according to the probe component arrangement 200a. In this example, the fiber optic connector 1026 is an embodiment of one of the fiber optic connectors described herein such as, for instance, a stainless steel fiber optic ferrule. In this example, the PCB 1046 is an embodiment of a PCB. In this example, the UV epoxy resin 1070 is an embodiment of the UV epoxy resin described herein. [0202] FIG.12B illustrates another example of a fully connected multi-modal fiber probe device according to at least one embodiment described herein. The probe device 1000 of FIG. 12B can include eight electrodes (e.g., the electrodes 140) respectively coupled to the PCB 1046, one microfluidic channel (e.g., the microfluidic channel 130) coupled to the microfluidic tube 1035, and one optical waveguide (e.g., the optical waveguide 120) coupled to the fiber optic connector 1026 Attorney Docket: 222204-2920 and/or an optic fiber 1025. The probe device 1000 of FIG. 12B can include the same attributes, structure, components, and functionality as that of the probe device 100 described herein and illustrated in FIG. 1 and fabricated according to the probe component arrangement 200a described herein and illustrated in FIG. 2A. The probe device 1000 of FIG. 12B can be fabricated by implementing the preform fabrication process 400a, the thermal drawing process 400b, the thermal tapering process 400c, and the backend connection process 400d described herein and illustrated in FIGS.4A, 4B, 4C, and 4D, respectively. [0203] FIG. 13 illustrates another example fabricated multi-modal fiber probe device 1300 (or “probe device 1300”) and an example implementation thereof according to various aspects and embodiments of the present disclosure. In the example shown, the probe device 1300 includes a tapered fiber probe structure 1310 having a tip region 1350 with an angled tip 1355. In this example, the probe device 1300 further includes a backend connector region 1360. In this example, the probe device 1300 is a fabricated embodiment of the probe device 500 described herein and illustrated in FIGS. 5A to 5C. In this example, the tapered fiber probe structure 1310, the tip region 1350, the angled tip 1355, and the backend connector region 1360 are fabricated embodiments of the tapered fiber probe structure 510, the tip region 550, the angled tip 555, and the backend connector region 560, respectively, of the probe device 500. [0204] FIG. 13 illustrates an example implementation of the probe device 1300 with one fiber optic connector 1026, one microfluidic tube 1035, and one PCB 1046 coupled to the backend connector region 1360 of the probe device 1300 at least in part by way of the UV epoxy resin 1070. In this example, the microfluidic tube 1035 is an embodiment of one of the microfluidic tubes 535 of the probe device 500. In this example, the fiber optic connector 1026 is an embodiment of the fiber optic connectors described herein such as, for instance, a stainless steel fiber optic ferrule. In this example, the PCB 1046 is an embodiment of a PCB. In this example, the UV epoxy resin 1070 is an embodiment of the UV epoxy resin described herein. [0205] FIG.13 illustrates another example of a fully connected multi-modal fiber probe device according to at least one embodiment described herein. The probe device 1300 of FIG. 12B can include three tetrodes (e.g., the tetrodes 540a, 540b, 540c) that each have four electrodes (e.g., the electrodes 542, 544, 546, 548) respectively coupled to the PCB 1046, one microfluidic channel (e.g., the microfluidic channel 530) coupled to the microfluidic tube 1035, and one optical waveguide (e.g., the optical waveguide 520) coupled to the fiber optic connector 1026 and/or an optic fiber 1025. The probe device 1300 of FIG. 13 can include the same attributes, structure, components, and functionality as that of the probe device 500 described herein and illustrated in FIGS.5A to 5C. The Attorney Docket: 222204-2920 probe device 1300 of FIG. 13 can be fabricated by implementing the preform fabrication process 700a, the thermal drawing process 700b, the thermal tapering process 700c, and the backend connection process 700d described herein and illustrated in FIGS.7A, 7B, 7C, and 7D, respectively. [0206] Disjunctive language, such as the phrase “at least one of X, Y, or Z,” unless specifically stated otherwise, is to be understood with the context as used in general to present that an item, term, or the like, can be either X, Y, or Z, or any combination thereof (e.g., X, Y, and/or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain embodiments require at least one of X, at least one of Y, or at least one of Z to be each present. [0207] As referenced herein, the term “user” refers to at least one of a human, an end-user, a consumer, a computing device and/or program (e.g., a processor, computing hardware and/or software, an application), an agent, a machine learning (ML) model and/or an artificial intelligence (AI) model, and/or another type of user that can implement and/or facilitate implementation of one or more embodiments of the present disclosure as described herein, illustrated in the accompanying drawings, and/or included in the appended claims. As referred to herein, the terms “includes” and “including” are intended to be inclusive in a manner similar to the term “comprising.” As referenced herein, the terms “or” and “and/or” are generally intended to be inclusive, that is (i.e.), “A or B” or “A and/or B” are each intended to mean “A or B or both.” As referred to herein, the terms “first,” “second,” “third,” and so on, can be used interchangeably to distinguish one component or entity from another and are not intended to signify location, functionality, or importance of the individual components or entities. As referenced herein, the terms “couple,” “couples,” “coupled,” and/or “coupling” refer to chemical coupling (e.g., chemical bonding), communicative coupling, electrical and/or electromagnetic coupling (e.g., capacitive coupling, inductive coupling, direct and/or connected coupling), mechanical coupling, operative coupling, optical coupling, and/or physical coupling. [0208] It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the disclosure. Many variations and modifications can be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

Claims

Attorney Docket: 222204-2920 CLAIMS Therefore, at least the following is claimed: 1. A multi-modal fiber probe device, comprising: a flexible tapered fiber probe structure comprising a micro-scale tip region at a first end and a macro-scale connector region at a second end opposite the first end; an optical waveguide positioned in and extending through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region; and a microfluidic channel formed in and extending through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region. The multi-modal fiber probe device of claim 1, further comprising: an electrode positioned in and extending through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region. 3. The multi-modal fiber probe device of claim 1, wherein the micro-scale tip region is at least partly defined by a crosscut of at least one of the flexible tapered fiber probe structure, the optical waveguide, or the microfluidic channel. 4. The multi-modal fiber probe device of claim 3, wherein the crosscut comprises an angled crosscut formed at a defined angle relative to a cross-section or longitudinal axis of the flexible tapered fiber probe structure. 5. The multi-modal fiber probe device of claim 3, wherein the micro-scale tip region comprises an angled tip positioned at the first end of the flexible tapered fiber probe structure, the angled tip being formed at a defined angle relative to a cross-section or longitudinal axis of the flexible tapered fiber probe structure. 6. The multi-modal fiber probe device of claim 1, further comprising: a backend connector region positioned adjacent to the macro-scale connector region of the flexible tapered fiber probe structure, the backend connector region comprising a fiber optic connector coupled to the optical waveguide and a microfluidic tube coupled to the microfluidic channel. Attorney Docket: 222204-2920 7. The multi-modal fiber probe device of claim 6, wherein the microfluidic tube comprises a polycarbonate tube and the fiber optic connector comprises a stainless steel fiber optic ferrule. 8. The multi-modal fiber probe device of claim 2, further comprising: a backend connector region positioned adjacent to the macro-scale connector region of the flexible tapered fiber probe structure, the backend connector region comprising a wire coupled to the electrode. The multi-modal fiber probe device of claim 8, wherein the backend connector region further comprises a pin connector coupled to the wire. 10. The multi-modal fiber probe device of claim 8, wherein the backend connector region further comprises a printed circuit board coupled to the wire. 11. The multi-modal fiber probe device of claim 2, wherein a dimension or cross-sectional area of an exposed portion of each of the optical waveguide, the microfluidic channel, and the electrode at the macro-scale connector region of the flexible tapered fiber probe structure is 10 to 30 times larger than a corresponding dimension or cross-sectional area of an exposed portion of each of the optical waveguide, the microfluidic channel, and the electrode at the micro-scale tip region of the flexible tapered fiber probe structure. 12. The multi-modal fiber probe device of claim 1, wherein each of a cross-section of the micro-scale tip region of the flexible tapered fiber probe structure and a corresponding cross-section of the macro-scale connector region of the flexible tapered fiber probe structure comprises a rectangular-shaped cross-section, an annular-shaped cross-section, or a circular-shaped cross- section. 13. The multi-modal fiber probe device of claim 1, wherein: the optical waveguide and the microfluidic channel are coaxially located in the flexible tapered fiber probe structure; and Attorney Docket: 222204-2920 the optical waveguide surrounds the microfluidic channel from the micro-scale tip region to the macro-scale connector region of the flexible tapered fiber probe structure. 14. The multi-modal fiber probe device of claim 13, wherein the flexible tapered fiber probe structure comprises an annular region that surrounds the optical waveguide and extends from the micro-scale tip region to the macro-scale connector region of the flexible tapered fiber probe structure, the annular region having an annular-shaped cross-section. 15. The multi-modal fiber probe device of claim 14, further comprising: an electrode positioned in and extending through the annular region from the micro-scale tip region to the macro-scale connector region of the flexible tapered fiber probe structure. 16. The multi-modal fiber probe device of claim 1, further comprising: an electrode positioned in and extending through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region of the flexible tapered fiber probe structure, wherein the flexible tapered fiber probe structure comprises a divider region that is positioned between the optical waveguide and the electrode and extends from the micro-scale tip region to the macro-scale connector region of the flexible tapered fiber probe structure. 17. The multi-modal fiber probe device of claim 1, further comprising: an electrode positioned in and extending through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region of the flexible tapered fiber probe structure, wherein: the flexible tapered fiber probe structure comprises a first divider region positioned between the optical waveguide and the microfluidic channel and a second divider region positioned between the microfluidic channel and the electrode; and the first divider and the second divider each extend from the micro-scale tip region to the macro-scale connector region of the flexible tapered fiber probe structure. 18. The multi-modal fiber probe device of claim 1, wherein the flexible tapered fiber probe structure comprises at least one of a polymer material or a polycarbonate material. Attorney Docket: 222204-2920 19. The multi-modal fiber probe device of claim 1, wherein the optical waveguide comprises a polycarbonate core and a poly(methyl 2-methylpropenoate) cladding. 20. The multi-modal fiber probe device of claim 2, wherein the electrode comprises a bismuth tin alloy electrode, a nichrome alloy electrode, a stainless steel alloy electrode, a gold or gold alloy electrode, a platinum electrode, or a tungsten electrode. 21. A process for fabricating a multi-modal fiber probe device, the process comprising: forming a fluidic channel and an optical waveguide in preform material to create a preform; performing a thermal drawing process on the preform to create a mini-preform; performing a thermal tapering process on the mini-preform to create a reduced cross-section region on the mini-preform; and crosscutting the reduced cross-section region to create a flexible tapered fiber probe structure comprising the fluidic channel and the optical waveguide extending through the tapered fiber probe structure from a micro-scale tip region at a first end of the flexible tapered fiber probe structure to a macro-scale connector region at a second end of the flexible tapered fiber probe structure. 22. The process of claim 21, further comprising: forming the fluidic channel, the optical waveguide, and an electrode in the preform. 23. The process of claim 21, wherein crosscutting the reduced cross-section region to create the flexible tapered fiber probe structure comprises: crosscutting the reduced cross-section region to create the micro-scale tip region at the first end of the flexible tapered fiber probe structure, the micro-scale tip region being at least partly defined by a crosscut of at least one of the flexible tapered fiber probe structure, the optical waveguide, or the fluidic channel. 24. The process of claim 21, wherein crosscutting the reduced cross-section region to create the flexible tapered fiber probe structure comprises: crosscutting the reduced cross-section region at a defined angle relative to a longitudinal axis of the reduced cross-section region to form the flexible tapered fiber probe structure with an angled tip. Attorney Docket: 222204-2920 25. The process of claim 21, further comprising: forming a backend connector region adjacent to the macro-scale connector region of the flexible tapered fiber probe structure. 26. The process of claim 25, wherein forming the backend connector region comprises: inserting a polycarbonate tube into the fluidic channel. 27. The process of claim 25, wherein forming the backend connector region comprises: coupling at least one of a fiber optic connector, a stainless steel fiber optic ferrule, or an optical fiber to the optical waveguide. 28. The process of claim 25, wherein forming the backend connector region comprises: coupling a wire to an electrode that is formed in and extends through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region of the flexible tapered fiber probe structure; and coupling a pin connector to the wire. 29. The process of claim 25, wherein forming the backend connector region comprises: coupling a wire to an electrode that is formed in and extends through the flexible tapered fiber probe structure from the micro-scale tip region to the macro-scale connector region of the flexible tapered fiber probe structure; and coupling a printed circuit board to the wire. 30. The process of claim 21, wherein forming the fluidic channel and the optical waveguide in the preform comprises: forming the fluidic channel and the optical waveguide in a polymer rod or a polycarbonate rod. 31. The process of claim 22, wherein forming the fluidic channel, the optical waveguide, and the electrode in the preform comprises: forming the fluidic channel through the preform and along a longitudinal axis of the preform from a first end to a second end of the preform; Attorney Docket: 222204-2920 forming the optical waveguide coaxially around the fluidic channel from the first end to the second end of the preform; and forming the electrode through an annular region of the preform, the annular region surrounding the optical waveguide and extending from the first end to the second end of the preform. 32. The process of claim 21, wherein performing the thermal tapering process comprises: applying a defined temperature of heat to the mini-preform to soften at least a portion of each of the mini-preform, the fluidic channel, and the optical waveguide; and pulling a first end and a second end of the mini-preform in opposite directions to create the reduced cross-section region of the mini-preform. The process for fabricating a fiber probe device of claim 21, wherein performing the thermal tapering process comprises: adjusting at least one of speed or travel distance of a motor used to pull a first end and a second end of the mini-preform in opposite directions to create the reduced cross-section region according to a defined geometry. 34. The process of claim 21, wherein the optical waveguide comprises a polycarbonate core and a poly(methyl 2-methylpropenoate) cladding. 35. The process of claim 22, wherein the electrode comprises a bismuth tin alloy electrode, a nichrome alloy electrode, a stainless steel alloy electrode, a gold or gold alloy electrode, a platinum electrode, or a tungsten electrode. 36. A multi-modal fiber probe device, comprising: a fiber probe structure comprising a first end and a second end opposite the first end; a silica optical waveguide positioned in and extending through the fiber probe structure from the first end to the second end of the fiber probe structure; and a tetrode positioned in and extending through the fiber probe structure from the first end to the second end of the fiber probe structure. 37. The multi-modal fiber probe device of claim 36, wherein the tetrode comprises: Attorney Docket: 222204-2920 a first electrode, a second electrode, a third electrode, and a fourth electrode each positioned in and extending through the fiber probe structure from the first end to the second end of the fiber probe structure. 38. The multi-modal fiber probe device of claim 36, further comprising: a microfluidic channel formed in and extending through the fiber probe structure from the first end to the second end of the fiber probe structure. 39. The multi-modal fiber probe device of claim 36, further comprising: a tip region formed at the first end of the fiber probe structure, the tip region being at least partly defined by a crosscut of at least one of the fiber probe structure, the silica optical waveguide, or the tetrode. 40. The multi-modal fiber probe device of claim 36, further comprising: a backend connector region positioned adjacent to the second end of the fiber probe structure, the backend connector region comprising: a backend portion of the silica optical waveguide extending from the second end of the fiber probe structure; and a backend portion of the tetrode extending from the second end of the fiber probe structure. 41. The multi-modal fiber probe device of claim 38, further comprising: a backend connector region positioned adjacent to the second end of the fiber probe structure, the backend connector region comprising a microfluidic tube coupled to the microfluidic channel. 42. The multi-modal fiber probe device of claim 36, wherein at least one of the silica optical waveguide or the tetrode has a melting temperature that is greater than a melting temperature of the fiber probe structure. 43. The multi-modal fiber probe device of claim 36, wherein: the fiber probe structure comprises a tapered fiber probe structure; and Attorney Docket: 222204-2920 the second end of the fiber probe structure has a dimension or cross-sectional area that is 10 to 30 times larger than a corresponding dimension or cross-sectional area of the first end of the fiber probe structure. 44. The multi-modal fiber probe device of claim 36, wherein the fiber probe structure comprises a uniform cross-sectional area from the first end to the second end of the fiber probe structure. 45. The multi-modal fiber probe device of claim 36, wherein each of a cross-section of the first end of the fiber probe structure and a corresponding cross-section of the second end of the fiber probe structure comprises a rectangular-shaped cross-section, an annular-shaped cross-section, or a circular-shaped cross-section. 46. The multi-modal fiber probe device of claim 36, wherein a dimension or cross- sectional area of an exposed portion of each of the silica optical waveguide and the tetrode at the second end of the fiber probe structure is 10 to 30 times larger than a corresponding dimension or cross-sectional area of an exposed portion of each of the silica optical waveguide and the tetrode at the first end of the fiber probe structure. 47. The multi-modal fiber probe device of claim 36, wherein a cross-sectional area of the silica optical waveguide at the first end of the fiber probe structure equals a corresponding cross- sectional area of the silica optical waveguide at the second end of the fiber probe structure. 48. The multi-modal fiber probe device of claim 36, wherein a cross-sectional area of the tetrode at the first end of the fiber probe structure equals a corresponding cross-sectional area of the tetrode at the second end of the fiber probe structure. 49. The multi-modal fiber probe device of claim 36, wherein the fiber probe structure comprises at least one of a tapered fiber probe structure or a flexible fiber probe structure. 50. The multi-modal fiber probe device of claim 36, wherein the tetrode comprises at least one of a bismuth tin alloy electrode, a nichrome alloy electrode, a stainless steel alloy electrode, a gold or gold alloy electrode, a platinum electrode, or a tungsten electrode. Attorney Docket: 222204-2920 51. The multi-modal fiber probe device of claim 36, wherein the fiber probe structure comprises at least one of a polymer material or a polycarbonate material. 52. The multi-modal fiber probe device of claim 36, wherein the fiber probe structure comprises an annular region that surrounds the silica optical waveguide and extends from the first end to the second end of the fiber probe structure, the annular region having an annular-shaped cross- section. 53. The multi-modal fiber probe device of claim 52, wherein the tetrode is positioned in and extends through the annular region from the first end to the second end of the fiber probe structure. 54. The multi-modal fiber probe device of claim 53, further comprising: a microfluidic channel formed in and extending through the annular region from the first end to the second end of the fiber probe structure. 55. The multi-modal fiber probe device of claim 36, further comprising: a microfluidic channel formed in and extending through the fiber probe structure from the first end to the second end of the fiber probe structure, wherein the fiber probe structure comprises a divider region that is positioned between the silica optical waveguide and the tetrode and extends from the first end to the second end of the fiber probe structure. 56. The multi-modal fiber probe device of claim 36, further comprising: a microfluidic channel formed in and extending through the fiber probe structure from the first end to the second end of the fiber probe structure, wherein: the fiber probe structure comprises a first divider region positioned between the silica optical waveguide and the microfluidic channel and a second divider region positioned between the microfluidic channel and the tetrode; and the first divider and the second divider each extend from the first end to the second end of the fiber probe structure. Attorney Docket: 222204-2920 57. The multi-modal fiber probe device of claim 36, further comprising: one or more additional tetrodes positioned in and extending through the fiber probe structure from the first end to the second end of the fiber probe structure, wherein at least one electrode of any of the one or more additional tetrodes comprises an electrode material that is different from an electrode material of each electrode of the tetrode. 58. The multi-modal fiber probe device of claim 39, wherein the crosscut comprises an angled crosscut formed at a defined angle relative to a cross-section or longitudinal axis of the fiber probe structure. 59. The multi-modal fiber probe device of claim 39, wherein the tip region comprises an angled tip positioned at the first end of the fiber probe structure, the angled tip being formed at a defined angle relative to a cross-section or a longitudinal axis of the fiber probe structure. 60. The multi-modal fiber probe device of claim 53, further comprising: one or more additional tetrodes positioned in and extending through the annular region from the first end to the second end of the fiber probe structure.