WO2021242173A1 - Integrated system for self-sustainable photonic modulation and continuous force sensing - Google Patents

Integrated system for self-sustainable photonic modulation and continuous force sensing Download PDF

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Publication number
WO2021242173A1
WO2021242173A1 PCT/SG2021/050287 SG2021050287W WO2021242173A1 WO 2021242173 A1 WO2021242173 A1 WO 2021242173A1 SG 2021050287 W SG2021050287 W SG 2021050287W WO 2021242173 A1 WO2021242173 A1 WO 2021242173A1
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WIPO (PCT)
Prior art keywords
triboelectric
tes
force
ain
example embodiment
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PCT/SG2021/050287
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French (fr)
Inventor
Bowei DONG
Qiongfeng SHI
Chengkuo Lee
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National University Of Singapore
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Publication of WO2021242173A1 publication Critical patent/WO2021242173A1/en

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    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/21Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  by interference
    • G02F1/225Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  by interference in an optical waveguide structure
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2203/00Function characteristic
    • G02F2203/15Function characteristic involving resonance effects, e.g. resonantly enhanced interaction

Definitions

  • the present invention relates broadly to an integrated system, to a method of generating modulation signals or sensor signals using the integrated system, and to a method of fabricating an integrated system, and in particular to a wearable triboelectric nano-energy-nano-system with self-sustainable photonic modulation and continuous force sensing.
  • Wearable electronics has rapidly advanced over the past decade to push the boundary of sensor technology towards conformal, flexible, and stretchable sensors for personalized healthcare [1- 3], smart displays [4-6], robotics [7,8], and Internet-of-Things (IoT) [9,10] applications.
  • Several transducing mechanisms have been investigated, including resistive [11], capacitive [12], thermoelectric [13,14], piezoelectric [15-17], triboelectric [18-20], and hybrid transducing mechanisms [21,22].
  • the piezoelectric and triboelectric transducing mechanisms are promising in realizing self-sustainable wearable electronic sensors to improve the convenience, wearing comfort, and to reduce the overall power consumption of sensing systems [23-28].
  • TESs triboelectric sensors
  • TESs pulse-like signals which are unstable and even cause stimuli information loss [54,55] .
  • the pulse-like signal is a practical limitation when TESs are connected to external circuits. Due to the transient current flow upon the electrostatic induction process, the TES’s electrical states determined by different stimuli shift rapidly to the electrical equilibrium, resulting in only a sharp pulse-like signal received by the external readout circuit with significant information loss.
  • One solution is to use a high impedance readout circuit to suppress current flows as well as the corresponding electrical state shifts [56,57.] Yet, an amplifying circuit is required to read the small current information, complicating the sensing system.
  • Another solution involves the utilization of deep learning techniques [58-60].
  • the DNN deep neural network
  • the DNN can extract the major features of the pulse-like signal and make correct decisions even in the presence of information loss. Nonetheless, the deep learning techniques require massive training data and can only make final decisions at the expense of ignoring intermediate states.
  • wearable photonics has been developed as a complementary technology for radio-frequency interference (RFI) free sensors [61-63], optogenetics [64,65], photomedicine [66], and high-speed transmission [67].
  • RFID radio-frequency interference
  • Several wearable photonic building blocks have been investigated including flexible waveguides [68-70], flexible light-emitting devices [71] and lasers [72,73], and flexible photodetectors [74,75].
  • the applications of triboelectric technology in nanophotonics have also enabled novel photodetection [76-78] and photoluminescence platforms [79-81]. However, how nanophotonics can help triboelectric technology has rarely been reported.
  • Embodiments of the present invention seek to address at least one of the above problems.
  • an integrated system comprising: a triboelectric device configured for generating a voltage output responsive to a force being applied to the triboelectric device; and a capacitive structure connected to the triboelectric device for applying the voltage output from the triboelectric device across the capacitive structure; wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and wherein the optical modulator is coupled to an optical source and is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device.
  • a method of generating modulation signals or sensor signals comprising the steps of: generating a voltage output responsive to a force being applied to a triboelectric device; applying the voltage output from the triboelectric device across the capacitive structure connected to the triboelectric device, wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and generating a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device using an optical source coupled to the optical modulator.
  • a method of fabricating an integrated system comprising: providing a triboelectric device configured for generating a voltage output responsive to a force being applied to the triboelectric device; and providing a capacitive structure connected to the triboelectric device for applying the voltage output from the triboelectric device across the capacitive structure; wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and wherein the optical modulator is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device.
  • Figure 1 shows a diagram illustrating a wearable NENS according to an example embodiment comprised of a tiny rigid AIN photonic module and a T-TES module serving as a high voltage source.
  • Figure 2(a)(i) shows the equivalent circuit model diagram of a wearable NENS according to an example embodiment.
  • Figure 2(a)(ii) shows diagrams illustrating the fundamental working principle of the integrated system according to an example embodiment.
  • Figure 2(a)(iii) shows diagrams illustrating the fundamental working principle of the integrated system according to an example embodiment.
  • FIG. 2(b)(i) shows an optical image of a textile TES (T-TES) for use in an example embodiment.
  • Figure 2(b)(ii) shows a scanning electron microscope (SEM) image of a conductive textile for use in an example embodiment.
  • Figure 2(b)(iii) shows an optical image of the AIN modulator for use in an example embodiment.
  • Figure 2(b)(iv) shows a tunneling electron microscope (TEM) image of the AIN modulator for use in an example embodiment.
  • TEM tunneling electron microscope
  • Figure 3(a) shows the T-TES open-circuit voltage under different applied periodic force, for use in an example embodiment.
  • FIG. 3(b) shows the T-TES short-circuit current under different applied periodic forces, for use in an example embodiment.
  • Figure 3(c) shows the dependence of open-circuit V pp on the impact force magnitude, for use in an example embodiment.
  • Figure 3(d) shows the load cell speed dependence of open-circuit V pp under constant impact force magnitude at 200 N, for use in an example embodiment.
  • Figure 3(e) shows output voltage and output power of the T-TES module at different load resistances, for use in an example embodiment.
  • Figure 3(f) shows a contour map showing the dependence of open-circuit V pp on impact force magnitude and contact area, for use in an example embodiment.
  • Figure 3(g) shows a schematic of the AIN MRR for use in an example embodiment.
  • Figure 3(h) shows the resonance characteristics of the AIN MRR with fixed g but varying R, for use in an example embodiment.
  • Figure 3(i) shows the resonance characteristics of AIN MRR with fixed R but varying g, for use in an example embodiment.
  • Figure 4(b) shows a zoom-in spectrum to the resonant wavelength at 1555.525 nm, for use in an example embodiment.
  • Figure 4(c) shows that the DC tuning of the resonant wavelengths in different AIN MRRs, for use in example embodiment.
  • Figure 4(d) shows the coupling gap dependence of the DC tuning efficiency, for use in an example embodiment.
  • Figure 4(e) shows the Radius dependence of the DC tuning efficiency, for use in an example embodiment.
  • Figure 4(f) shows the AC modulation of the AIN modulator at 100 MHz, for use in an example embodiment.
  • Figure 4(g) shows the AC modulation of the AIN modulator at 3 GHz, for use in an example embodiment.
  • Figure 4(h) shows the accumulated modulation signals at 3, 4, and 5 GHz, for use in an example embodiment.
  • Figure 5(a) shows an image of a spacer TES (S-TES) for use in an example embodiment.
  • FIG. 5(b) shows an image of a smart glove with a textile TES (T-TES) for use in an example embodiment.
  • Figure 5(c) shows an image of a short AIN MZI modulator for use in an example embodiment.
  • Figure 5(d) shows an image of a long AIN MZI modulator for use in an example embodiment.
  • Figure 5(e) shows a tunneling electron microscope (TEM) image of the tunable aluminum nitride (AIN) waveguide’s cross-section, for use in an example embodiment.
  • TEM tunneling electron microscope
  • Figure 6(a) shows the S-TES is composed of a negative triboelectric part of PTFE/Al/foam/PET (illustrated in part in an exploded view) and a positive triboelectric part of Al/foam/PET, with a sponge spacer in between, for use in an example embodiment.
  • Figure 6(b) shows the measured V oc of the S-TES under different Fs of 18 N, 52 N, 80 N and 170 N (at a constant VF of 100 mm/min), for use in an example embodiment.
  • Figure 6(c) shows the output voltage (V) and power (P) performance of the S-TES at different external resistances (R’), with F of 170 N and VF of 100 mm/min, for use in an example embodiment.
  • Figure 6(d) shows V oc of S-TES according to an example embodiment rapidly increases from 19 V at 10 N to 81 V at 30 N, then slowly rises to 92 V at 60 N, and saturates thereafter (> 60 N).
  • Figure 6(e) shows V oc of S-TES according to an example embodiment is not affected by VF from 100 mm/min to 500 mm/min as implied by the near-zero linearly fitted slope, showing good stability across different V FS .
  • Figure 6(f) shows V oc of S-TES according to an example embodiment can practically respond exactly to the force profile induced by hand control, fully reflecting the force information.
  • Figure 6(g) shows a textile TES for use in an example embodiment.
  • Figure 6(h) shows the testing results of the T-TES 502 under different Fs of 10 N, 40 N, 80 N, and 170 N (at a constant VF of 100 mm/min), for use in an example embodiment.
  • Figure 6(i) shows the V and P performance of the T-TES at different R’s, for use in an example embodiment.
  • Figure 6(j) shows that V oc of the T-TES gradually increases from 45 V at 10 N to 77 V at 115 N, after which V oc becomes relatively stable, for use in an example embodiment.
  • FIG. 6(k) shows the effect of different VFS, V 0C of the T-TES is also consistent under different VFS from 100 mm/min to 500-mm/min, for use in an example embodiment.
  • Figure 6(1) shows the V oc profile generated by human hand control of the T-TES 502, for use in an example embodiment.
  • Figure 7(b) shows a free-spectral range (FSR) of 5.81 nm in the telecommunication wavelength range of 1520 nm to 1600 nm for the short AIN MZI modulator, for use in an example embodiment.
  • FSR free-spectral range
  • Figure 7(c) shows the zoom-in wavelength spectrum in Figure 7(c) showing a sine fit with an R-square of 0.98.
  • Figure 7(e) shows an FSR of 7.14 nm of the long AIN MZI modulator, for use in an example embodiment.
  • Figure 7(f) shows the zoom-in wavelength spectrum in Figure 7(e) showing a sine fit with an R-square of 0.99.
  • Figure 7(g) shows the direct current (DC) tuning characteristics of the short AIN MZI modulator, for use in an example embodiment.
  • Figure 7(h) shows the direct current (DC) tuning characteristics of the long AIN MZI modulator, for use in an example embodiment.
  • Figure 7(i) shows the dependence of the phase change on V for the short and long AIN MZI modulator, for use in an example embodiment.
  • Figure 7(j) shows the T - V curve for the short and long AIN MZI modulator, for use in an example embodiment.
  • Figure 8(a) shows the temporal spectrum of normalized T in the short AIN MZI modulator under 10 kHz AC modulation signal with different magnitudes, for use in an example embodiment.
  • Figure 8(b) shows the temporal spectrum of normalized T in the short AIN MZI modulator under 10 kHz AC modulation signal with different magnitudes, for use in an example embodiment.
  • Figure 8(c) shows the quantitative relation between normalized tuning and V pp , for use in an example embodiment.
  • Figure 8(d) shows the temporal T response of the short MZI under 100-kHz AC modulation, for use in an example embodiment.
  • Figure 8(e) shows the temporal T response of the long MZI under 100-kHz AC modulation, for use in an example embodiment.
  • Figure 8(f) shows the measured results indicate a 3-dB bandwidth of 0.9 MHz in the long AIN MZI modulator 503 and 1.1 MHz in the short AIN MZI modulator, for use in an example embodiment.
  • Figure 8(g) shows that when a voltage pulse that sharply rises from 0 V to [27 x N] V is applied to the long MZI, where N is an integer ranging from 1 to 7, it is observed that N peak and troughs appear in the temporal T spectrum when [27 x N] V is applied, and T finally reaches the same level as T at 0 V, for use in an example embodiment.
  • Figure 9(a) shows the impact force magnitude dependence of V pp applied on the AIN MRR and the corresponding resonant wavelength shift, for use in an example embodiment.
  • Figure 9(b) shows the load cell speed dependence of V pp applied on the AIN MRR and the corresponding resonant wavelength shift, for use in an example embodiment.
  • Figure 9(c) shows a contour map showing the dependence of resonant wavelength shift on impact force magnitude and contact area, for use in an example embodiment.
  • Figure 9(d) shows the T-TES output voltage waveform generated by periodic motion of the force gauge and the characteristic T-TES stages in terms of contact/separation mode, according to an example embodiment.
  • Figure 9(e) shows the resonance wavelength shift induced by T-TES voltage output and the corresponding optical transmission waveform at the operation wavelength of 1555.455 nm, according to an example embodiment.
  • Figure 9(f) shows the resonance wavelength shift induced by T-TES voltage output and the corresponding optical transmission waveform at the operation wavelength of 1555.48 nm, according to an example embodiment.
  • Figures 9(g) shows the resonance wavelength shift induced by T-TES voltage output and the corresponding optical transmission waveform at the operation wavelength of 1555.525 nm, according to an example embodiment.
  • Figure 9(h) shows the resonance wavelength shift induced by T-TES voltage output and the corresponding optical transmission waveform at the operation wavelength of 1555.531 nm, according to an example embodiment.
  • Figure 9(i) shows the resonance wavelength shift induced by T-TES voltage output and the corresponding optical transmission waveform at the operation wavelength of 1555.555 nm, according to an example embodiment.
  • Figure 10(a) shows the impact force magnitude, the resultant applied voltage on the AIN modulator, together with the optical transmission spectrum at different load cell speeds of 900 mm/min, (b) 700 mm/min, and (c) 500 mm/min in a NENS according to an example embodiment.
  • Figure 10(b) shows the impact force magnitude, the resultant applied voltage on the AIN modulator, together with the optical transmission spectrum at different load cell speeds of 700 mm/min, in a NENS according to an example embodiment.
  • Figure 10(c) shows the impact force magnitude, the resultant applied voltage on the AIN modulator, together with the optical transmission spectrum at different load cell speeds of 500 mm/min in a NENS according to an example embodiment.
  • Figure 10(d) shows zoom-in of the spectra in Figures 10(a) to a complete operation cycle.
  • Figure 10(e) show zoom-in of the spectra in Figures 10(b) to a complete operation cycle.
  • Figures 10(f) show zoom-in of the spectra in Figures 10(c) to a complete operation cycle.
  • Figure 10 (g) shows a calibration curve showing the one-to-one correspondence of the optical transmission and the impact force magnitude at different load cell speeds, according to an example embodiment.
  • Figure 10(h) shows the proposed physical model that describes the integrated system according to an example embodiment.
  • Figure 11(a) shows S-TES’s output voltage (VS-TES) under different Fs at 100 mm/minm according to an example embodiment.
  • Figure 11(b) shows the VF dependence of VS-TES and the corresponding resultant T according to an example embodiment.
  • Figure 11(c) shows one force cycle divided into four regions as illustrated by the differently shaded areas, according to an example embodiment.
  • Figure 11(d) shows the corresponding electrostatically induced VS-TES, according to an example embodiment.
  • Figure 11(e) shows three critical force states are labeled by (T), (2), and (3) respectively, according to n example embodiment.
  • Figure 11(f) shows the temporal T spectrum, according to an example embodiment.
  • Figure 11(g) shows the detailed temporal F-VS-TES-T spectra in 11 - 14 s, according to an example embodiment.
  • Figure 11(h) shows the one-to-one corresponding data extracted from Figure 11(g) to derive the resultant relation between T and F in the S-TES, according to an example embodiment.
  • Figure 12 shows the measured and fitted relation between V and F with a one to one correspondence (data is extracted from Figure 11(g), according to an example embodiment.
  • Figure 13 shows the measured and fitted relation between T and F, according to an example embodiment.
  • Figure 14 shows that measured and fitted V-F relation, according to an example embodiment.
  • Figure 15 shows that measured and fitted T-F relation, according to an example embodiment.
  • Figure 16(a) shows T-TES’s output voltage (VS-TES) under different Fs at 100 mm/minm according to an example embodiment.
  • Figure 16(b) shows the VF dependence of VT-TES and the corresponding resultant T according to an example embodiment.
  • Figure 16(c) shows one force cycle divided into four regions as illustrated by the differently shaded areas, according to an example embodiment.
  • Figure 16(d) shows the corresponding electrostatically induced VT-TES, according to an example embodiment.
  • Figure 16(e) shows three critical force states are labeled by (T), (2), and (3) respectively, according to n example embodiment.
  • Figure 16(f) shows the temporal T spectrum, according to an example embodiment.
  • Figure 16(g) shows the detailed temporal F-VT-TES-T spectra in 11 - 14 s, according to an example embodiment.
  • Figure 16(h) shows the one-to-one corresponding data extracted from Figure 11(g) to derive the resultant relation between T and F in the T-TES, according to an example embodiment.
  • Figure 17(a) shows the schematic of the measurement system for optical Morse code transmission, according to an example embodiment.
  • Figure 17(b) illustrates the custom-built software can translate the detected signal into the pre defined alphabets whose array could convey the desired messages, according to an example embodiment.
  • Figure 17(c) demonstrates the transmission of all the 26 alphabets, according to an example embodiment.
  • Figure 17(d) shows a message array conveying ‘HINUS’, according to an example embodiment.
  • Figure 17(e) shows a photo and graphs illustrating a monitoring scenario of continuous force when the textile wearable NENS is attached on a human arm, according to an example embodiment.
  • Figure 17(f) shows a photo and graphs illustrating a monitoring scenario of continuous force when the textile wearable NENS is attached on a human sole, according to an example embodiment.
  • Figures 18(a) shows a schematic illustration of the S-TES, for use in an example embodiment.
  • Figure 18(b) shows a schematic of the short AIN MZI modulator lwith an arm length (Larm) of 2.16 mm and footprint of 0.81 mm 2 , for use in an example embodiment.
  • Figure 18(c) shows the linear relation between Transmission and Force in the 35 - 60 N force range with a sensitivity of 0.659 mV/N, according to an example embodiment.
  • Figures 18(d) shows a schematic illustration of the elastic T-TES, for use in an example embodiment.
  • Figure 18(f) shows the linear relation between Transmission and Force in the 7 - 70 N force range with a sensitivity of 0.174 mV/N, and 75 - 110 N force range with a sensitivity of - 0.793 mV/N, according to an example embodiment.
  • Figure 19(a) shows the schematic circuit diagram of a robotic hand control system according to an example embodiment.
  • Figure 19(b) shows the optical signal output of the thumb and the corresponding signals of the other fingers from the glove in the system of Figure 19(a), according to an example embodiment for controlling the finger number and the movement speed of the robotic hand.
  • Figure 20(a) shows screenshots of a flower planting process in the AR space, according to an example embodiment.
  • Figure 20(b) shows the output signals of the fingers in the flower planting process, according to an example embodiment.
  • Figure 20(c) shows a screenshot of continuous showering the flower in the AR space, according to an example embodiment.
  • Figure 20(d) shows the curve of optical output in continuous showering step, according to an example embodiment.
  • Figure 21 shows a schematic drawings illustrating an integrated system according to an example embodiment.
  • Figure 22 shows a flowchart illustrating a method of generating modulation signals or sensor signals according to an example embodiment.
  • Figure 23 shows a flowchart illustrating a method of fabricating an integrated system, according to an example embodiment.
  • Wearable photonics offers a promising platform to complement the fostering complex wearable electronics system by providing high-speed data transmission channel and robust optical sensing path.
  • embodiments of the present invention address this issue by integrating a voltage-based aluminum nitride (AIN) modulator and textile triboelectric sensor (T-TES) on a wearable platform to form a nano- energy-nano- system (NENS).
  • the T-TES transduces the mechanical stimulations into electrical signals based on the coupling of triboelectrification and electrostatic induction.
  • the self-generated high-voltage from the T-TES is applied to the AIN modulator and boosts its modulation efficiency regardless of AlN’s moderate Pockels effect.
  • AIN modulator’s capacitive nature enables the open-circuit operation mode of T-TES, providing the integrated NENS according to example embodiment with continuous force sensing capability which is notably uninfluenced by operation speeds.
  • optical Morse code transmission and continuous human motion monitoring are demonstrated. Leveraging the design flexibility of TENG and AIN nanophotonic circuits for force monitoring, various linear sensitivities independent of force speed can be achieved in different force ranges.
  • a smart glove based on the NENS is provided according to an example embodiment to realize continuous real-time robotic hand control and virtual/augmented reality (VR/AR) interaction.
  • VR/AR virtual/augmented reality
  • the generated high voltage output, the excellent optical tuning feature, and the open-circuit operation mode of the wearable NENS according to embodiments of the present invention can pave the way to future self-sustainable wearable tunable photonics for communication, healthcare monitoring, and human-machine interface applications.
  • embodiments of the present invention provide the first implementation of integrating the two domains of technologies, namely TENG and AIN photonics.
  • the synergy between triboelectric technology and AIN photonics according to example embodiments can offer extra benefits to both sides.
  • the high-voltage from TENG can be applied to the AIN modulator with negligible degradation and effectively enhance the modulation efficiency through bypassing the limited tuning efficiency restricted by AlN’s moderate Pockets effect.
  • Complementarity, the capacitor nature of AIN modulator and the optical transmission capability of photonic system could be another possible solution to continuously monitor the TENG output in a compact and easy-to-implement manner other than the conventional open-circuit voltage/charge approach which relies on bulky and complicated external electrical circuits.
  • integrating a TENG sensor with a micro parallel-plate capacitor sandwiching an aluminum nitride (AIN) nanophotonic waveguide enables the TENG sensor to work in the open-circuit condition with a negligible electrical state shift.
  • Embodiments of the present invention can benefit wearable self-sustainable electronics and photonics for applications ranging from human machine interface, smart home, robotics, and augmented reality / virtual reality interactions.
  • Figure 1 shows a diagram illustrating a wearable NENS 100 according to an example embodiment comprised of a tiny rigid AIN photonic module 102 and a T-TES module 104 serving as a high voltage source. Mechanical, electrical, and optical signals can be transduced in the system to achieve wide photonic modulation and continuous force sensing.
  • the details of the AIN photonics module 102 and the exploded view of the T-TES 104 are presented. Examples of the potential applications of the system include, but are not limited to, wireless control/communication, healthcare monitoring, human machine interface.
  • Figure 2(a)(i) shows the equivalent circuit model diagram and (ii & iii) show diagrams illustrating the fundamental working principle of the integrated system.
  • Figure 2(b)(i) shows an optical image of the T-TES 104
  • Figure 2(b)(ii) shows a scanning electron microscope (SEM) image of a conductive textile
  • Figure 2(b)(iii) shows an optical image of the AIN modulator 102
  • Figure 2(b)(iv) a tunneling electron microscope (TEM) image of the AIN modulator 102.
  • SEM scanning electron microscope
  • TEM tunneling electron microscope
  • the integration of aluminum nitride (AIN) modulator 102 and wearable textile triboelectric sensor (T-TES) 104 takes advantage of both devices and enables their synergy.
  • the wearable triboelectric-AIN nano-energy-nano-system (NENS) 100 according to an example embodiment with self-sustainable photonic modulation and continuous force sensing functions features a wearable platform comprised of the tiny rigid AIN photonic module 102 and a T-TES module 104 as shown in Figure 1.
  • the self-sustainable photonic modulation is realized by using the T- TES 104 as a power supply.
  • the T-TES 104 transduces the mechanical stimulations to electrical signals based on the coupling of triboelectrification and electrostatic induction.
  • the self-generated electrical signals are then applied to the AIN modulator 102 to generate modulated optical signals, which are routed to photodetectors e.g. 108 and converted to electrical readouts.
  • the continuous force sensing is realized by using the AIN modulator 102 for sensing signal readout.
  • Such a readout scheme decouples the sensing path and the signal readout path so that high optical readout signals can be received even when the electrical sensing circuit is operated with low output current..
  • the AIN modulator 102 is composed of an AIN microring resonator (MRR) 110 sandwiched by a pair of top and bottom electrodes 112, 114 to leverage AlN’s rl3 electro-optic (EO) coefficient.
  • the electrodes 112, 114 are connected to the T-TES 104 output.
  • T-TES module 104 flexible Ecoflex and nitrile layers on conductive textiles are adopted as the negative and positive friction surface respectively. Upon physical contact, opposite charges with equal quantity are generated on the two surfaces due to their different electron affinities. Upon separation of the two charged surfaces, the built-up electric potential difference will induce an output voltage in the external circuit.
  • a thin spacer is sandwiched between two functional layers for separation. The entire structure is encapsulated by two additional pieces of non-conductive textiles.
  • Figure 2(a) explains the basic working mechanism of the system 100 according to an example embodiment.
  • the T-TES 104 can be considered as a serial connection of an alternating current (AC) voltage source and a capacitor, while the AIN modulator 102 acts as a parallel plate capacitor.
  • the AIN MRR 110 is initially working on resonance where the optical transmission is zero at the output 116 ( Figure 2(a)(ii)).
  • Zero-bias is applied to the AIN MRR 110 when the T-TES 104 is in the contact mode since opposite charges are neutralized at the contact interface.
  • a high-voltage is applied to the AIN MRR 110 when the T-TES 104 is in the separation mode due to electrostatic induction.
  • the generated strong electric field (E-field) alters AlN’s refractive index through Pockels effect and consequently changes the resonant condition.
  • the AIN MRR 110 then operates in the off-resonance condition, and measurable optical transmission is received at the output 116 ( Figure 2(a)(iii)).
  • the intensity of the optical transmission depends on the voltage from the T-TES 104.
  • Figure 2(b) shows an optical image of the wearable T-TES 104 (Figure 2(b)(i)), the SEM image of a top view of the conductive ( Figure 2(b)(ii)), the optical image of the AIN modulator 102 ( Figure 2(b)(iii)) as well as its tunneling electron microscope (TEM) image ( Figure 2(b)(iv)) of a perspective view from one side.
  • Figure 2(b) shows an optical image of the wearable T-TES 104 ( Figure 2(b)(i)), the SEM image of a top view of the conductive ( Figure 2(b)(ii)), the optical image of the AIN modulator 102 ( Figure 2(b)(iii)) as well as its tunneling electron microscope (TEM) image ( Figure 2(b)(iv)) of a perspective view from one side.
  • TEM tunneling electron microscope
  • the conversion between physical quantities and the related physical effects enable the information flow in an integrated triboelectric sensor (TES)/nanophotonics sensing system according to an example embodiment.
  • the human inputs a force signal (F), causing a mechanical deformation (Ax) in the TES according to the stress-strain relation.
  • the mechanical deformation is transduced to an electrical signal (V) through the triboelectrification and electrostatic induction process.
  • V electrical signal
  • the electrical signal is then applied to the nanophotonic readout circuit and transduced into a photonic signal (T) by the electro-optic Pockels effect.
  • the photonic signal is finally read out for e.g. robotic control and VR/AR interactions. Characterization of the T-TES and the AIN Modulator according to example embodiments
  • Figure 3(a) shows the T-TES open-circuit voltage under different applied periodic force.
  • Figure 3(b) shows the T-TES short-circuit current under different applied periodic forces.
  • Figure 3(c) shows the dependence of open-circuit V pp on the impact force magnitude.
  • Figure 3(d) shows the load cell speed dependence of open-circuit V pp under constant impact force magnitude at 200 N.
  • Figure 3(e) shows output voltage and output power of the T-TES module 104 at different load resistances.
  • Figure 3(f) shows a contour map showing the dependence of open- circuit V pp on impact force magnitude and contact area.
  • Figure 3(g) shows a schematic of the AIN MRR.
  • Figure 3(h) shows the resonance characteristics of the AIN MRR with fixed g but varying R.
  • Figure 3(i) shows the resonance characteristics of AIN MRR with fixed R but varying g.
  • the fabricated T-TES generates sufficient voltage and power to enable enhanced photonic modulation and even sustain the entire wearable NENS according to an example embodiment.
  • the basic characterization of the T-TES is first conducted using a force gauge testing system that provides impact forces with controllable magnitudes by a load cell with varying speeds.
  • Figure 3(a) shows the typical open-circuit voltage waveforms of the T-TES under different impact force magnitudes of 41 N, 77 N, and 197 N, respectively (at 900 mm/min load cell speed). Clear improvement of the open-circuit voltage along with the increasing impact force magnitude can be observed.
  • the short-circuit current of the T-TES under the same impact force magnitudes is presented in Figure 3(b), exhibiting the same improvement trend.
  • V pp As expected, highly stable V pp are observed at various speeds as a result of T-TES ’s open-circuit operation mode, demonstrating that the V pp of T-TES is only determined by the impact force magnitude but independent of the load cell speed in open-circuit operation mode.
  • V pp from different resistor loads when they are connected to the T-TES (at 200 N force) are measured.
  • a maximum output power of 64 pW can be achieved when the connected resistor load is 33 MW.
  • the output performance of the T-TES is also measured by finger tapping in the scenarios of using one, two and three fingers.
  • a high-performance AIN modulator is used for high-speed optical transmission, on-chip computation, and effective tuning in a system according to an example embodiment.
  • an array of AIN modulators is fabricated.
  • the characteristic of the AIN modulator is fundamentally determined by the ring radius (R) and coupling gaps (g) of the AIN MRR 300 ( Figure 3(g)).
  • R ring radius
  • g coupling gaps
  • the resonant wavelength lk is solely determined by R.
  • R The free spectral range (FSR) associated with the spacing between different RS will change with R as well.
  • Figure 4(b) shows a zoom-in spectrum to the resonant wavelength at 1555.525 nm.
  • Figure 4(c) shows that the DC tuning of the resonant wavelengths in different AIN MRRs.
  • Figure 4(d) shows the coupling gap dependence of the DC tuning efficiency.
  • Figure 4(e) shows the Radius dependence of the DC tuning efficiency.
  • Figure 4(f) shows the AC modulation of the AIN modulator at 100 MHz.
  • Figure 4(g) shows the AC modulation of the AIN modulator at 3 GHz.
  • Figure 4(h) shows the accumulated modulation signals at 3, 4, and 5 GHz.
  • the optical transmission spectrum of the AIN MRR around the telecommunication C-Band is presented in Figure 4(a).
  • An average insertion loss of 5.73 dB and a free spectral range (FSR) of 3.612 nm is demonstrated.
  • Figure 4(b) zooms into the resonant wavelength at 1555.525 nm, revealing a 3-dB bandwidth of 34 pm which corresponds to Q factor of 45,750.
  • An ER of 21.5 dB is accompanied.
  • the performance of the AIN modulator according to an example embodiment under different applied biases is investigated.
  • the direct current (DC) tuning result is plotted in Figure 4(c).
  • the resonant wavelength can be continuously tuned in the range from 1553.366 nm to 1553.523 nm and 1553.551 nm to 1553.706 nm respectively when a -200 - 200 V DC bias is applied.
  • a linear relationship between AR and the applied voltage is observed with a tuning efficiency of 0.39 pm/V.
  • the high-speed modulation capability of the AIN modulator is investigated by applying square waves with 10 V pp and + 5 V bias.
  • ER the device is working at 1555.525 nm which is the resonant wavelength that results in zero transmission without applying bias.
  • the modulation is efficient at 100 MHz modulation frequency.
  • RF radio frequency
  • the lowest and highest optical transmission is 3.7 mV and 32.4 mV respectively, corresponding to an ER of 9.4 dB.
  • Figure 4(g) plots the modulation results at 3 GHz.
  • the AIN modulator Since the RF source has a maximum speed of 12.5 GHz, some RF signal distortions away from a square waveform are observed at 3 GHz in the clock signal.
  • the AIN modulator still carries the input RF signal efficiently despite some small phase delays and a reduced ER of 2.12 dB.
  • the rise time t,- and fall time rr (defined by 10 % and 90 % of the step height) is 60 ps and 80 ps respectively.
  • a rough estimation of the cut-off frequency can be calculated as 2 GHz by:
  • the cut-off frequency is further verified by the optical transmission signal accumulated temporally as shown in Figure 4(h).
  • the light is effectively modulated by the 3 GHz RF input.
  • the AIN modulator fails to carry the RF signal at 5 GHz.
  • t r of around 40 ps is estimated, which is close to the measured rise time and fall time.
  • the limiting factor in the AIN modulator is the long photon lifetime.
  • a modulator with a lower Q factor can be designed to reduce t r .
  • the theoretical modulation speed limited by the photon lifetime can reach 20 GHz.
  • the top and bottom electrodes (compare numerals 112, 114 in Figure 1) design also needs careful consideration to ensure low RC delay for use in example embodiments, as will be appreciated by a person skilled in the art.
  • One system according to an example embodiment has a spacer TES (S-TES) 500 (Figure 5(a)) integrated with a short AIN MZI modulator 501 ( Figure 5(c)).
  • the other one has a textile TES (T-TES) 502 ( Figure 5(b)) integrated with a long AIN MZI modulator 503 ( Figure 5(d)).
  • S-TES spacer TES
  • T-TES textile TES
  • Figure 5(d) 502 Figure 5(b)
  • the images of the four actual devices for the two integrated systems are shown in Figures 5(a) to (d), and the characteristics of them are investigated individually in Figures 6 and 7.
  • a tunneling electron microscope (TEM) image of the tunable aluminum nitride (AIN) waveguide’s cross-section is shown in Figure 5(e), showing the waveguide is sandwiched by a pair of top and bottom electrodes.
  • TEM tunneling electron microscope
  • the S-TES 500 is composed of a negative triboelectric part of PTFE/Al/foam/PET (illustrated in part in an exploded view in Figure 6(a) and a positive triboelectric part of Al/foam/PET, with a sponge spacer in between.
  • the S- TES 500 is tested using a force gauge testing system that applies forces with controllable magnitudes (F) and speeds (VF).
  • the measured V oc of S-TES 500 under different Fs of 18 N, 52 N, 80 N and 170 N are shown in Figure 6(b), where V oc is positively related to F.
  • the output voltage (V) and power (P) performance of the S-TES 500 at different external resistances (R’) is also measured ( Figure 6(c)), with F of 170 N and VF of 100 mm/min.
  • V oc of S-TES 500 rapidly increases from 19 V at 10 N to 81 V at 30 N, then slowly rises to 92 V at 60 N, and saturates thereafter (> 60 N).
  • V oc is not affected by VF from 100 mm/min to 500 mm/min as implied by the near-zero linearly fitted slope, showing good stability across different VFS ( Figure 6(e)).
  • V oc Since V oc is solely determined by F and independent of VF, it can be adopted as the output indicator for real-time force monitoring. As further illustrated in Figure 6(f), V oc can practically respond exactly to the force profile induced by hand control, fully reflecting the force information. It is also noteworthy that V oc can be maintained at different levels, which is an important characteristic of TESs 500 working in the open-circuit condition.
  • another TES fabricated by textile materials i.e., textile TES (T- TES) 502
  • T- TES textile TES
  • the T-TES 502 is composed of a negative eco-flex coated conductive carbon cloth, a narrow-gap spacer, a positive nitrile layer with another carbon cloth, encapsulated by two pieces of non-conductive textiles for electrical insulation.
  • the testing results of the T-TES 502 under different Fs of 10 N, 40 N, 80 N, and 170 N (at a constant VF of 100 mm/min) are illustrated in Figure 6(h), indicating a positive relation between V oc and F as well.
  • the maximum P of 1.97 pW can be achieved at a matched R’ of 65.4 MOhm.
  • V oc of the T-TES 502 gradually increases from 45 V at 10 N to 77 V at 115 N, after which V oc becomes relatively stable.
  • the force sensitive range is extended from 60 N to 115 N, but V and P are both smaller.
  • V OC of T-TES 502 is also consistent under different VFS from 100 mm/min to 500-mm/min ( Figure 6(k)). According to the V oc profile generated by human hand control as shown in Figure 6(1), it is confirmed that V 0c can be precisely controlled when the T-TES 502 works in the open- circuit condition.
  • the TES 500/502 can be regarded as a voltage source V with an internal resistance R0 while the external resistance is R’.
  • the output power of the TES (P) is: Equation S 1
  • AIN MZI modulators 501, 503 are characterized to ensure that they can carry the TES s’ 500, 502 voltage signals effectively.
  • a short and a long AIN MZI modulator 501, 503 are designed to integrate with the S-TES 500 and the T-TES 502, respectively, according to example embodiments.
  • the T-TES’s 502 saturation force is larger, its V 0c is lower.
  • a longer AIN MZI modulator 503 is used to provide a strong electric-field (E-field) / light interaction for maintaining a high nanophotonic readout resolution.
  • the short AIN MZI modulator 501 with the arm length of L arm 2.16 mm occupies a footprint of only 0.81 mm 2 ( Figure 7(a)).
  • a free-spectral range (FSR) of 5.81 nm in the telecommunication wavelength range of 1520 nm to 1600 nm is presented in Figure 7(b).
  • the zoom-in wavelength spectrum in Figure 7(c) shows a sine fit with an R-square of 0.98, illustrating the high quality of the short AIN MZI modulator 501 whose optical transmission (T) is theoretically governed by interference.
  • T In the short AIN MZI modulator 501 at 1548 nm, T almost changes monotonically as V varies monotonically from - 200 V to 200 V. On the contrary, in the long AIN MZI modulator 503 at 1553.8 nm, T changes periodically under similar applied V.
  • the higher voltage sensitivity of the long AIN MZI modulator 503 can be attributed to its longer F arm that provides a stronger E-field / light interaction.
  • a sine fit is adopted for Figure 7(j) and a period of 716 V and 54 V is obtained in the short and the long AIN MZI modulator 501, 503, respectively, corresponding to their n p values of 358 V and 27 V.
  • the two n p values are consistent with the n p values extracted from Figure 7(i). Quantitatively, the ratio of the n p values is 13.11 while the ratio of the two F arm s is 12.99. The two close ratios reveal the proportionality between phase change and F arm under DC biases. The proportionality is further analyzed and confirmed by a theoretical analysis.
  • Equation S2 Equation S2
  • Equation S6 The last term can be ignored since it involves the product of two small values, and Equation S6 is reduced to: Equation S7
  • phase change is proportional to length L of the AIN MZI arm.
  • FIG 8(a) and Figure 8(b) present the temporal spectrum of normalized T in the short and the long AIN MZI modulator respectively, under 10 kHz AC modulation signal with different magnitudes.
  • the term ‘normalized tuning’ is defined as the opening of the temporal spectrum of the modulated T, i.e. the difference between the high and the low T value.
  • V pp peak to peak voltage
  • the temporal T response of the short and the long MZI 501, 503 under 100-kHz AC modulation are plotted in Figure 8(d) and Figure 8(e) respectively.
  • the optical waveforms can reproduce the voltage waveforms, demonstrating the effective transduction from electrical signal to photonic signal using the AIN MZI modulators at a 100- kHz data transmission rate.
  • AIN MZI modulators’ speed limit a 3- dB measurement was implemented using a vector network analyzer (VNA).
  • VNA vector network analyzer
  • the measured results shown in Figure 8(f) indicate a 3-dB bandwidth of 0.9 MHz in the long AIN MZI modulator 503 and 1.1 MHz in the short AIN MZI modulator.
  • the curve for the short AIN MZI has been moved up by 5 dB manually for visual clarity.
  • the around 1-MHz modulation speed achieved in both AIN MZI modulators allows nanophotonic readout circuits to capture TESs’ signals with a temporal resolution of around 1 ps, which can satisfy most of the applications related to human/machine interactions, according to example embodiments.
  • a voltage pulse that sharply rises from 0 V to [27 x N] V is applied to the long MZI, where N is an integer ranging from 1 to 7. It is observed that N peak and troughs appear in the temporal T spectrum when [27 x N] V is applied, and T finally reaches the same level as T at 0 V.
  • Figure 9(a) shows the impact force magnitude dependence of V pp applied on the AIN MRR and the corresponding resonant wavelength shift.
  • Figure 9(b) shows the load cell speed dependence of V pp applied on the AIN MRR and the corresponding resonant wavelength shift.
  • Figure 9(c) shows a contour map showing the dependence of resonant wavelength shift on impact force magnitude and contact area.
  • Figure 9(d) shows the T-TES output voltage waveform generated by periodic motion of the force gauge and the characteristic T-TES stages in terms of contact/separation mode.
  • Figures 9(e-i) show the resonance wavelength shift induced by T- TES voltage output and the corresponding optical transmission waveform at the operation wavelength of (e) 1555.455 nm, (f) 1555.48 nm, (g) 1555.525 nm, (h) 1555.531 nm, (i) 1555.555 nm.
  • the best self-sustainable photonic modulation is achieved in (h), according to an example embodiment.
  • the two electrodes from the T-TES are connected to the top and bottom electrodes that sandwich the AIN MRR (compare e.g. Figure 1), forming the electrical-photonic tuning system.
  • the output characteristics of the T-TES when it is integrated with the AIN modulator in a NENS according to an example embodiment are firstly studied. As shown in Figure 9(a), the V pp increases rapidly with impact force magnitude in the low impact force magnitude range and saturates at 235 V gradually in the high impact force magnitude range. This relationship has the same trend as the open-circuit voltage from the standalone T-TES in Figure 3(c), with the only difference in the absolute voltage magnitude.
  • the reduction of voltage magnitude is mainly caused by the Baby Neill Constant (BNC) cables that are used to connect the AIN modulator and the T-TES for characterization.
  • BNC Baby Neill Constant
  • the T-TES will preferably be directly connected to the AIN modulator without BNC cables and introduces almost no voltage reduction due to the minuscule capacitance of the AIN modulator.
  • the corresponding A R can be obtained by the 0.39 pm/V sensitivity because the electrical signal from the T-TES is far slower than the intrinsic response time of the AIN modulator. Around 100 pm AAR can be achieved in the integrated system.
  • the dependence of V pp and corresponding AAR on the load cell speed (at 200 N impact force magnitude) is also investigated and presented in Figure 9(b).
  • V pp and AAR are both substantially unaffected by the load cell speed and only determined by the impact force magnitude. This independence of V pp on the load cell speed further confirms that the T-TES is working in the open-circuit condition due to the capacitive nature of the AIN modulator. Testing of the T-TES as a human-machine interface is implemented. With finger tapping as the triggering, the resultant AAR shows notable increment with impact force magnitudes and contact areas. As for the AIN modulator, its optical characteristics are completely maintained since the electrical connection does not affect the optical path.
  • the detailed self-sustainable photonic modulation mechanism and phenomenon including the open-circuit voltage from the T-TES and the transmission spectrum from the AIN modulator 102 in an integrated NENS is presented in Figure 9(d) to Figure 9(i).
  • the open-circuit voltage from the T-TES 900 has a periodic alternating waveform that is similar to a square-wave (Figure 9(d)). It is generated by the periodic motion of the force gauge. The deviation from the square-wave is caused by the dissipation of electrons to the humid environment.
  • the detailed T-TES ’s 900 output characteristics (Figure 9(d)) and the corresponding AA R ( Figure 9(e)) in the AIN modulator are examined in one cycle.
  • the load cell is in full contact with the T-TES with the pre-set impact force magnitude (contact mode of the T-TES 900), and the respective open-circuit voltage is zero. Then from Stage 1 to Stage 2, the load cell is moving up to the zero position and the two triboelectric layers are gradually separated from each other (separation mode of the T-TES 900) due to the device restoring force. Electric potential is rapidly built up with the separation, inducing a significant increment in the open-circuit voltage. The negative output is determined by the direction of electrode connection. The large negative voltage blueshifts AR of the AIN modulator. At Stage 2, the load cell is back to the zero position (separation mode of the T-TES 900) and the open- circuit voltage reaches the negative maximum.
  • AR at this stage is at the leftmost position ( Figure 9(e)).
  • Stage 3 the slow decrement of open-circuit voltage is due to charge dissipation of the system when the load cell is held still at zero position.
  • AR slowly redshifts.
  • Stage 3 to Stage 4 the load cell is moving down to contact with the T-TES 900 again (contact mode of the T-TES 900), thus the open-circuit voltage decreases towards zero rapidly during this period. Accordingly, a rapid redshift of AR of the AIN modulator is observed.
  • the open-circuit voltage at Stage 4 is above zero with maximum impact force magnitude, due to the drifting of the open-circuit voltage.
  • the open-circuit voltage of T-TES 900 is drifted back to zero (Stage 1) and the next cycle begins.
  • the optical transmission waveform is strongly dependent on the operation wavelength.
  • the optimal operation wavelength should be identified for the system according to various example embodiments for the best self-sustainable photonic modulation performance.
  • the optical transmission waveform almost reproduces the T-TES 900 output voltage waveform.
  • the operation wavelength is 1555.48 nm which is closer to AR
  • a different waveform featuring a sharp trough from Stage 1 to Stage 2 is presented in Figure 9(f).
  • AR consecutively blue shifts strongly, redshifts slightly, and redshifts strongly.
  • the observed transmission from the previous stage is also marked in transparent circle.
  • the optical transmission is high since the operation wavelength is to the left of AR.
  • AR approaches, coincides with, and further shifts to the left side of the working wavelength, resulting in a sharp trough in the transmission.
  • AR slowly redshifts approaches, coincides with, and further shifts to the right side of the working wavelength, inducing a slow transaction of decrement and increment in transmission.
  • Stage 3 to Stage 4 a significant increment in transmission can be observed due to the rapid redshift of AR.
  • the open-circuit voltage gradually decreases back to zero when load cell maintains full contact with the T-TES 900. Due to the small decrement of voltage, AR only slightly blueshifts maintaining the high transmission level.
  • the operation principle is the same.
  • Figure 9(g) shows that when the operation wavelength is exactly at AR, the optical transmission waveform features a sharp trough from Stage 3 to Stage 4.
  • the best self- sustainable photonic modulation according to an example embodiment can be achieved when the operation wavelength is at 1555.531 nm, slightly longer than AR, as illustrated in Figure 9(h).
  • a square optical transmission waveform is obtained without the presence of any sharp trough.
  • “1” and “0” can be readily defined to realize binary operation.
  • the photonic modulation depth becomes shallow while the optical transmission waveform being the reverse of the initial T-TES 900 output voltage waveform.
  • a superior advantage of the integrated wearable NENS is the capability of enabling T-TES 900 to work under the open-circuit mode in a compact and easy-to-implement manner.
  • the photonic module helps with transmitting the open-circuit sensing signal out in-situ through the optical signal, which can be detected by a photodetector circuit.
  • the wearable NENS according to example embodiments is working similarly to Figure 9(e) where the optical transmission spectrum replicates the waveform of the T-TES 900 modulating signal.
  • Figures 10(a-c) shows the impact force magnitude, the resultant applied voltage on the AIN modulator, together with the optical transmission spectrum at different load cell speeds of, (a) 900 mm/min, (b) 700 mm/min, and (c) 500 mm/min in a NENS according to an example embodiment.
  • Figures 10(d-f) show zoom-in of the spectra in Figures 10(a-c) to a complete operation cycle, (d) 900 mm/min, (e) 700 mm/min, and (f) 500 mm/min.
  • Figure 10 (g) shows a calibration curve showing the one-to-one correspondence of the optical transmission and the impact force magnitude at different load cell speeds.
  • Figure 10(h) shows the proposed physical model that describes the integrated system according to an example embodiment.
  • the T-TES is described by a parallel plate capacitor where the two plates are connected by a spring.
  • the AIN MRR is described by a resonator with a Lorentzian resonant lineshape. More specifically, The detailed waveforms of the impact force, the resulting induced voltage on the AIN modulator, and the optical transmission spectrum are shown in Figure 10(a) to Figure 10(c), with different load cell speeds of 900, 700 and 500 mm/min.
  • Figure 10(d) to Figure 10(f) present the zoom-in waveforms in a complete cycle, corresponding to the three load cell speeds respectively.
  • a cycle can be divided into three stages from left to right with respect to the force status applied on the T-TES.
  • Stage I the load cell is approaching and gradually compresses the T- TES with the pre-set impact force magnitude. Due to the reduced gap between the top and the bottom friction layers, the induced voltage on AIN modulator decreases gradually with the impact force magnitude. As a result, the optical transmission from the AIN modulator 102 increases, following the same trend as the induced voltage visually.
  • the load cell is in tight contact with the T-TES with the pre-set impact force magnitude; and the induced voltage is maintained at low level.
  • the induced voltage is not zero at this stage is due to the open-circuit voltage shift arisen from the measurement instrument, while the small decrement of the induced voltage towards zero can be attributed to the slow charge dissipation of the system. A similar trend can also be found from the optical transmission of the AIN modulator.
  • Stage (III) the load cell is removed from and gradually releases the T-TES. Initially, the impact force magnitude decreases significantly from the full contact state to the critical contact state where the two friction surfaces are still in contact with each other, but the impact force magnitude is at a very low level. Thus, during this period, the induced voltage from the T-TES on the AIN modulator remains high.
  • the two friction surfaces start to separate from each other; and the induced voltage on the AIN modulator gradually increases accordingly.
  • the same trend can also be found in the optical transmission waveform.
  • the absolute value of the induced voltage as well as the optical transmission in the AIN modulator can reach and maintain a monotonous value that corresponds solely to the absolute magnitude of the impact force but is substantially not affected by the load cell speeds.
  • both the induced voltage and the optical transmission exhibit a higher increment or decrement rate, but the maximum values still maintain the same. It means that the optical transmission of the AIN modulator can follow the exact trend of the applied force on the T-TES, providing an advanced and easy-to-implement approach for continuous force sensing compared to the conventional open-circuit electrical voltage measurement.
  • a direct relationship of the resultant optical transmission and the impact force magnitude can be observed in Figure 10(g) in the NENS according to an example embodiment, which is extracted from Stage I in Figure 10(d) to Figure 10(f).
  • This relationship serves as the calibration curve for continuous force sensing.
  • a calibration curve should have a one-to-one relationship.
  • the monotonically increasing optical transmission with the increasing impact force magnitude for the NENS according to an example embodiment fulfills the calibration curve requirement.
  • Theoretical analysis is implemented to provide an analytical formula that can depict the full relationship between the impact force magnitude and the optical transmission, instead of only the measured discrete points.
  • a physical model is proposed to describe the integrated system ( Figure 10(h)).
  • the T-TES is described by a parallel plate capacitor where the two plates with constant charge +Q and -Q are connected by a spring dominated by the stress-strain relation.
  • the AIN MRR is described by a resonator with a Lorentzian resonant lineshape where the resonant wavelength is determined by the E-field across the parallel plate capacitor.
  • the force on spring (F) determines the parallel plate capacitor’s voltage (V) and subsequently causes AAR through the Pockels effect.
  • the resultant optical transmission (T) at the specific/operating wavelength is tuned continuously and follows the Lorentzian lineshape.
  • the relation between the optical transmission and the impact force magnitude can be expressed as: where T is the optical transmission and F is the impact force magnitude.
  • D, K, N, B are fitting parameters where D is the separation between two plates without applying force, K and N are two coefficients in the stress-strain relationship, B is a mathematical fitting parameter without physical meaning.
  • the data in Figure 10(g) is fitted well by the derived expression. More significantly, the fitted calibration curve is independent of the speed of the impact force. This benefits the continuous force sensing in practical applications using NENS according to example embodiments.
  • the integration of TESs and nanophotonic readout circuits can also be conveniently achieved through connecting the two TES electrodes to the pair of electrodes sandwiching the AIN MZI waveguide according to example embodiments.
  • the TES output voltage (VTES) is applied on the AIN MZI modulators, inducing an E-field across the AIN waveguide to change AlN’s refractive index through the electro-optic Pockels effect. In this way, T of AIN MZI carries the information delivered by VTES since T is governed by the refractive index.
  • FIG. 11(a) shows S-TES’s output voltage (VS-TES) under different Fs at 100 mm/min.
  • the dependence of VS-TES on F follows a similar trend as Figure 3(a) that shows S-TES’s V 0c without any integrated nanophotonic readout circuit.
  • VS-TES abruptly increases from 16 V at 10 N to 80 V at 30 N, then gradually rises to 90 V at 60 N, and saturates afterward due to the full activation of surface charges in the triboelectrification process.
  • the resultant T changes correspondingly to VS-TES.
  • Region I refers to the zero-force stage where the two triboelectric layers are fully separated.
  • the corresponding electrostatically induced VS-TES (- 25 V as shown in Figure 11(d)) maintains the lowest T (10 mV as shown in Figure 11(f)) in the nanophotonic readout circuit.
  • region II F is gradually exerted on the S-TES so that the top triboelectric layer is approaching the bottom one.
  • VS-TES increases and leads to the rise of T.
  • Region III corresponds to the period when F exceeds the saturation value (60 N as shown in Figure 11(a)) while the two triboelectric layers are in tight contact.
  • the resultant VS-TES keeps unchanged (90 V), so is T (28 mV).
  • region IV the two triboelectric layers begin to separate apart from each other when F starts to drop.
  • F decreases to ⁇ 60 N
  • VS-TES and T begin to fall back to the lowest value.
  • the stimulus in the form of F mainly interacts with the integrated S-TES/nanophotonic sensing system in region II.
  • region II is further explored in detail.
  • Three critical force states are labeled by (T), (2) , and (3) respectively.
  • the load cell touches the top surface of the S-TES and F starts to increase.
  • the two triboelectric layers are pressed towards each other without contact.
  • F increases gradually due to the small elastic coefficient provided by the sponge spacer, causing a slight increase of VS-TES but a negligible change in T.
  • the two triboelectric layers are in contact, so F starts boosting due to the abrupt change of elastic coefficient.
  • the corresponding VS-TES and T shoot up accordingly.
  • F boosts to the maximum around 190 N, VS-TES has already saturated at 90 V at State (3) of 60 N, with 27-mV T. Afterwards, F is maintained before it drops to 0 N.
  • the integrated TES/nanophotonics sensing system serves to read force information (F) from photonic readout (T), the one-to-one corresponding data extracted from Figure 11(g) to derive the resultant relation between T and F in the S-TES as:
  • Equation S8 Equation S8
  • FIG. 12 shows the measured relation between V and F with a one to one correspondence.
  • the data is extracted from Figure 11(g).
  • a boundary condition obtained from Figure 11(g) is:
  • Equation S8 leads to: Equation s 10
  • Equation S 11 Fitting the data in Figure 13 using Equation S 11, the resultant equation is presented in Equation (B4) above. The fitted curve is shown in the solid line with an R-square of 0.981 in Figure 13.
  • T-TES integrated textile triboelectric sensor
  • N-TES integrated textile triboelectric sensor
  • the derivation process is the same.
  • the V-F relation and T-F relation, as well as the fitted curves, are presented in Figure 14 and Figure 15 respectively.
  • the resultant equation governing the T-F relation is presented in Equation (B5).
  • the design flexibility of TESs was further leveraged to extend the applicable force monitoring range of the integrated TES/nanophotonics sensing system according to an example embodiment.
  • the T-TES has a broader force monitoring range whose saturation point happens at 115 N instead of only 60 N in the S-TES.
  • the voltage output of the T-TES (VT-TES) is lower than VS-TES. Consequently, the long AIN MZI modulator with higher voltage sensitivity is adopted to be integrated with the T-TES to compensate for the lower VT-TES.
  • the long one is working at a destructive interference at 1551.7 nm when VT-TES is the lowest.
  • FIG 16(a) presents VT-TES and the corresponding T characteristics of the integrated T-TES/nanophotonics sensing system according to an example embodiment under different Fs.
  • VT-TES gradually increases from 40 V at 10 N to 65 V at 115 N with T falling from 32 mV at 10 N to 20 mV at 40 N, and then increasing to 28 mV at 115 N.
  • Figurel6 (b) shows the V F -dependence of VT-TES and T. Using linear fitting, straight fitted lines with slopes of - 0.008 and 0.008 are derived for VT-TES and T respectively, suggesting that the T-TES is working in the open-circuit condition.
  • Figure 16(c) to Figure 16(f) explain the working principle of the integrated T-TES/nanophotonics sensing system according to an example embodiment.
  • one force cycle can be split into four regions with the same definitions as Figure 11(c).
  • Region I and Region III are similar to Figure 11.
  • Region II and Region IV where the temporal F spectrum shows sharp edges show different features.
  • the temporal T spectrum in these two regions presents oscillations that produce a peak and a trough.
  • 5 characteristic force states were identified, namely (T), (2), (3), (4) and (5).
  • Figures 17(a-d) show a NENS 1700 according to an example embodiment in an optical Morse code transmission application - (a) Characterization setup, (b) Interface of the optical Morse code reader software, (c) the 26 distinguished alphabets transmitted by the optical Morse code, (d) Optical transmission of the information ‘HINUS’ using the wearable NENS.
  • Figures 17(e&f) show a NENS 1700 according to an example embodiments in a continuous human motion monitoring application. The optical transmission spectrum (top) and the corresponding translated impact force magnitude (bottom) resulted from - (e) Arm patting, and (f) Walking. The calibration relies on the calibration curve in Figure 10(g).
  • wearable photonics is data transmission.
  • the wearable NENS 1700 can be leveraged for optical Morse code transmission.
  • Figure 17(a) shows the schematic of the corresponding measurement system.
  • the optical signal is converted to the voltage signal by the photodetector and subsequently directed to a microcontroller unit (MCU) that serves as the interconnect between the integrated system and the computer.
  • MCU microcontroller unit
  • the Keithley electrometer together with the oscilloscope help to monitor the real-time voltage output from the T-TES of the NENS 1700.
  • the custom-built software can translate the detected signal into the pre-defined alphabets whose array could convey the desired messages, as illustrated in Figure 17(b).
  • Figure 17(c) demonstrates the transmission of all the 26 alphabets.
  • a message array conveying ‘HINUS’ is shown in Figure 17(d). In principle, all alphabets combinations are feasible to transmit arbitrary meaningful messages.
  • wearable photonics Another key application of wearable photonics is sensing.
  • continuous force sensing can be achieved to take advantage of merits from both sides.
  • the continuous human motion monitoring is demonstrated using a wearable NENS 1702, 1704 according to an example embodiment.
  • cyclic finger tapping is applied on the device during the first 5 s. Then the fingers remain in contact with the device and press the device periodically for around 2 s. The same motion pattern is repeated starting from the cyclic finger tapping (Figure 17(e) top panel).
  • Figures 18(a-c) show an elastic S-TES 1800 integrated with short AIN MZI modulator 1802 according to an example embodiment -
  • Figures 18(d-f) show a T-TES 1810 integrated with long AIN MZI modulator 1812 according to an example embodiment -
  • an elastic S-TES 1800 is integrated with a short AIN Mach-Zehnder Interferometer (MZI) modulator 1802 to realize linear force sensitivity of 0.659 mV/N in the range of 35 - 60 N.
  • MZI Mach-Zehnder Interferometer
  • a T-TES 1810 is integrated with a long AIN MZI modulator 1812 to achieve linear force sensitivity of 0.174 mV/N in 7 - 70 N and - 0.763 mV/N in 75 - 110 N.
  • the design flexibility is advantageously provided by the broad material availability of S-TES 1800, T-TES 1810 and the critical impedance difference between AIN photonics 1802, 1812 and S-TES 1800, T-TES 1810.
  • a smart glove according to an example embodiment is fabricated based on the NENS as a human-machine-interface (HMI) for continuous real-time robotic control and virtual reality / augmented reality (VR/AR) interactions.
  • HMI human-machine-interface
  • VR/AR virtual reality / augmented reality
  • smart gloves as HMIs have two major advances. One is integrating numerous sensors on a single glove for accurate tactile sensing [82]. Enabled by the large number of sensors, tactile sensing with great details can be achieved. Using deep learning methodology, the sensing information can reconstruct the hand motion exactly. The other direction is using a single glove for multivariant sensing, including temperature, strain, humidity, light, etc. In this way, the smart glove can mimic the complete human sensory system [83].
  • the smart glove according to an example embodiment features self-sustainability and continuous real-time monitoring.
  • Figure 19(a) shows the schematic circuit diagram of the robotic hand 1902 control system according to an example embodiment.
  • Figure 19(b) shows the optical signal output of the thumb and the corresponding signals of the other fingers from the glove 1900 according to an example embodiment for controlling the finger number and the movement speed of the robotic hand 1902.
  • Inserts show photographs of the glove 1900 on the human hand and the robotic hand 1902, respectively.
  • Figure 19(a) illustrates the circuit diagram adopted in an HMI robotic control application, as well as the physical quantities transduction that allows the information flow, according to an example embodiment.
  • the information in the mechanical form is firstly converted into the electrical form via T-TES sensors e.g. 1904, 1905, then transforms into the photonic form by applying the electrical signal to AIN MZI modulator 1906.
  • the photonic readout is used for robotic hand 1902 control.
  • Five individual sensors e.g. 1904, 1905 are knitted on five fingertips of the glove 1900.
  • the thumb sensor 1905 is connected to the long AIN MZI modulator 1906 to achieve the open- circuit condition; and the generated photonic signal is converted to voltage by a photodetector which is then connected to a microcontroller unit (MCU) for the analog-to-digital conversion.
  • MCU microcontroller unit
  • more than one of the sensors may be connected to a corresponding modulator in different example embodiments.
  • the other four T_TESs e.g. 1904 on the other fingers are directly connected to the MCU.
  • the number of sensors directly connected to the MCU may be different in different example embodiments.
  • the MCU here acts as the medium between the NENS 1910 according to an example embodiment and the robotic hand 1902, enabling real-time information transfer from T-TES sensors e.g. 1904, 1905 to the robotic hand 1902.
  • Robotic hand 1902 control is demonstrated using different movement speeds and numbers of human fingers.
  • Fig. 19(b) when a balloon is pinched with the smart glove 1900, pulse-like signals are generated at the moment of contact and separation for the index, middle, ring and little finger, while the thumb signal shows continuous real-time changing curves related with force F and the duration of force, VF.
  • TENG sensors only two states, namely grasp or release, can be achieved in one operation cycle due to the transient pulse-like signal without any intermediate state.
  • the robotic hand 1902 perfectly follows the movement of the human hand with the gradual grasping and releasing process as detected by the T-TES on the thumb operating in open-circuit condition.
  • the insert images show in detail three states during the process, including the zero-F (box 1912), the medium-F (box 1914), and the maximum-F (box 1916) states.
  • the number of fingers can be manipulated.
  • Figure 19(b.i, iii, iv, and v) when pinching and loosening the balloon using various numbers of fingers, the signals in each finger channel exhibit that the robotic hand 1902 responds with the same fingers and duration of force as the human hand.
  • Figure 20(a) shows screenshots of the flower planting process in the AR space. Inserts show detailed views of the corresponding gestures in each step.
  • Figure 20(b) shows the output signals of the fingers in the flower planting process.
  • Figure 20(c) shows a screenshot of continuous showering the flower in the AR space. The Insert shows pressing the T-TES for nanophotonic readout.
  • Figure 20(d) shows the curve of optical output in continuous showering step. Inserts show the 3 showering angles of the watering can be controlled by different forces Fs.
  • discrete actions in the AR flower planting process are defined by different gestures. Firstly, a flower is picked up when the index finger is contacted with the thumb, (i). Then, the separation between the index finger and the thumb commands planting the flower in the flowerpot, (ii). Subsequently, by contacting the middle finger with the thumb, scissors are picked up, (iii). And with one more contact of the middle finger with the thumb, the flower is pruned, (iv). It should be mentioned that the flower can be pruned for multiple times as long as the middle finger is contacted with the thumb. Afterward, once the ring finger is contacted with the thumb, the scissors are put down, (v).
  • FIG. 20(b) shows the corresponding electrical output signals of the four fingers (other than the thumb) in each step.
  • the continuous real-time control capability is leveraged in the showering step by using the NENS according to an example embodiment (Fig. 20(c)).
  • the showering angle of the can be adjusted in response to the states of an elastic S-TES sensor2000 placed on the table upon pressing.
  • Figure 20(d) shows the continuous real-time changing curve of the photonic signal during the pressing process; and three specific showering angles under three pressing states with different forces Fs are displayed in the inserts.
  • a wearable triboelectric / aluminum nitride Nano-Energy-Nano-System (NENS) with self-sustainable photonic modulation and continuous force sensing functions is provided according to example embodiments.
  • NENS Nano-Energy-Nano-System
  • embodiments of the present invention aim at optical modulation and address the power consumption issue in modulator systems by integrating voltage -based AIN modulator and T-TES/S-TES power source.
  • the synergy between AIN modulator and T-TES/S-TES brings two major advantages to the integrated system according to example embodiments.
  • AlN’s moderate Pockels effect, the enhanced modulation is achieved in AIN modulators enabled by T-TES’s/S-TES's high voltage output.
  • T-TES’s/S-TES's open-circuit operation mode can be facilitated by AIN modulator’s capacitive nature and consequently provides a compact and easy-to- implement system for continuous sensing.
  • the characterization of individual AIN modulator and e.g. T-TES for use in example embodiments shows superior device performance respectively in terms of high-quality resonance lineshape (Q factor > 30,000, ER > 21 dB), stable DC tuning efficiency (0.4 pm/V), high AC modulation speed (> 3 GHz), and high voltage output (V pP > 300 V). Negligible performance degradation is observed after the system integration according to example embodiments because the AIN modulator can inherit the high-voltage from T-TES thanks to their capacitive nature.
  • Optical Morse code transmission and continuous human motion monitoring are demonstrated according to example embodiments based on the two unique advantages respectively.
  • various linear force sensitivities are achieved in different force ranges. Integrating e.g. an elastic T-TES sensor with a short 2.16-mm-long AIN MZI modulator according to an example embodiment, a linear force sensitivity of 0.659 mV/N is achieved in the range of 35 - 65 N.
  • a linear force sensitivity of 0.659 mV/N is achieved in the range of 35 - 65 N.
  • the force sensing range is extended to cover 7 - 110 N with a complementary linear sensitivity of 0.174 mV/N in 7 - 70 N and - 0.763 mV/N in 75 - 110 N.
  • the linear force sensitivities are independent of force speeds, providing an important good property for practical applications.
  • a smart glove based NENS according to an example embodiments is provided and continuous real-time control of robotics and VR/AR interactions are demonstrated, highlighting the stable, continuous real time, and information-lossless features.
  • the demonstrated integrated system according to example embodiments is not limited to the specified TENG sensors described for example embodiments, but applicable generally to all sensors that rely on the triboelectrification and electrostatic induction mechanisms.
  • the integrated system according to example embodiments is not limited to AIN for the optical modulators described for example embodiments, but applicable generally to optical materials with Pockels effect, so that these materials can be tuned by the high voltage from the TENGs.
  • the NENS according to an example embodiment provides a versatile solution for self-sustainable wearable sensors for HMI applications.
  • This hybrid integration is a crucial demonstration toward future self-sustainable wearable photonic ICs and tunable photonic sensors, which will find significant applications, including:
  • Embodiments of the present invention can provide one or more of the following features and associated benefits/advantages:
  • the AIN MZI modulator and AIN MRR share the same fabrication process.
  • the fabrication started from a commercially available 8-inches Si wafer insulated by a thin layer of Si0 2 .
  • the bottom electrode was formed by a 120-nm TiN layer and a 50-nm S13N4 layer. Then the bottom electrode was covered by a planarized 2-pm S1O2 layer for insulation.
  • the 2-pm S1O2 layer also served as the bottom cladding for light confinement in AIN waveguide.
  • a layer of 400-nm AIN was deposited after which a 200-nm S1O2 layer was deposited and patterned as the hard mask for AIN etching.
  • S-TES spacer triboelectric sensor
  • PTFE was utilized as the negative triboelectric material while aluminum foil served as the positive triboelectric material and electrode material.
  • PET was utilized as the substrate of S-TES.
  • a thin foam and a sponge were utilized as the spacer and the stage respectively. It should be noted that the foam here acted as the stage to ensure the contact of two triboelectric layers because simply pressing the sponge was unable to make sure of the contact.
  • the surface areas of substrates are 5 x 5 cm 2 and those of the inner stages, electrode materials, and triboelectric materials are 3 x 3 cm 2 .
  • the thickness of the fabricated S-TES is 1 cm in total.
  • T-TES textile triboelectric sensor
  • eco-flex and nitrile films were used as the triboelectric materials, carbon cloth as the electrode material, foam as the spacer, and textile as the sealing material for the whole device.
  • the surface area of this fabricated sensor is 1.5 x 1.5 cm 2 and the whole thickness is about 3 mm.
  • eco-flex solution was prepared by mixing component A and B in an 1:1 weight ratio. Then, it was uniformly blade-coated on one piece of carbon cloth. After solidifying, a negative triboelectric layer was obtained. Meanwhile, a nitrile film was attached to one side of another piece of carbon cloth as the positive triboelectric layer.
  • the eco-flex and the nitrile layer were assembled face to face and in parallel with four foam strips in between as the spacer, which were arranged over the four edges of the two layers.
  • two textile pieces were attached individually to the other side of both carbon cloths for insulation and sealing.
  • threads sewing the four edges of the device to enhance the attachment between layers a T-TES could be obtained.
  • a force gauge system (Mecmesin Multitest 2.5-i Test system) was utilized to apply forces with different magnitudes and speeds on the triboelectric sensors, and enable contact and separation process of the two triboelectric layers.
  • a programable electrometer (Keithley 6514) was utilized to test the open-circuit voltage, and an oscilloscope (Agilent DSO-X3034A) was connected to it for real-time data acquisition.
  • a tunable laser source Keysight, 81960A Tunable Laser
  • the light was guided through a single-mode-maintaining polarization controller, then focused to the inversed tapered waveguide by a tapered fiber (OZ Optics, TSMJ- 3A-1550-9/125-0.25-18-2.5-14-3-AR), and finally guided to AIN MZI modulators.
  • the voltage was applied to the AIN MZI modulators through a GSG probe with a 100- pm pitch (MPI, T26A GSG100).
  • a tunable DC voltage supply (Agilent, E3631A) was amplified by 20 times using a voltage amplifier (FLC Electronics, A400DI) before connected to the GSG probe.
  • a power meter Keysight, 81636B Power Sensor
  • a waveform generator HP, 33120A was used as the power supply whose voltage was also amplified by 20 times before connected to the GSG probe.
  • the modulated optical signals are amplified by an erbium-doped fiber amplifier (Thorlabs, EDFA100S) before captured by a high-speed photodetector (Thorlabs, DET08CFC/M.) and converted into RF output which was then captured by an oscilloscope (Agilent Technologies, DS093004L).
  • the general characterization is similar to that of the AIN MZI modulators and triboelectric sensors. The differences are as follows: Firstly, the voltage applied on the AIN MZI modulators is provided by connecting the GSG probe with triboelectric sensors. Secondly, for the demonstration part, the contact and separation process was controlled by the human hand instead of the force gauge.
  • Figure 21 shows a schematic drawings illustrating an integrated system 2100 according to an example embodiment, comprising a triboelectric device 2102 configured for generating a voltage output responsive to a force being applied to the triboelectric device 2102; and a capacitive structure 2104 connected to the triboelectric device 2102 for applying the voltage output from the triboelectric device 2102 across the capacitive structure 2104; wherein the capacitive structure 2104 comprises an optical modulator 2106 disposed between opposing electrodes 2108, 2110; and wherein the optical modulator 2106 is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device 2102 and hence the force applied to the triboelectric device 2102.
  • the optical modulator 2106 may comprise a microring resonator.
  • the optical modulator 2106 may comprise a Mach-Zehnder interferometer.
  • the triboelectric device 2102 may be textile based.
  • the triboelectric device 2102 may comprise material layers disposed on opposite sides of a flexible spacer structure.
  • the integrated system may comprise a plurality of triboelectric devices including the triboelectric device 2102 configured for generating the voltage output responsive to the force being applied thereto.
  • One or more of the plurality of triboelectric devices may be configured for generating output voltage spikes responsive to a force being applied thereto.
  • the one or more triboelectric devices configured for generating output voltage spikes responsive to the force being applied thereto may be connected directly to a micro controller unit.
  • the micro controller may be configured to receive the modulated optical signal via a photodetector.
  • the integrated system may comprise a plurality of capacitive structures, each of the plurality of capacitive structures comprising a corresponding optical modulator disposed between opposing electrodes, and each of the plurality of capacitive structures being connected to a corresponding one of the plurality of triboelectric devices for applying the voltage output from the corresponding triboelectric device across said each capacitive structure, wherein each of the optical modulators may be configured to generate a modulated optical signal responsive to the output voltage from the corresponding triboelectric device and hence the force applied to the corresponding triboelectric device.
  • the integrated system may comprise a glove as carrier of the plurality of triboelectric devices.
  • FIG. 22 shows a flowchart 2200 illustrating a method of generating modulation signals or sensor signals according to an example embodiment.
  • a voltage output is generated responsive to a force being applied to a triboelectric device.
  • the voltage output from the triboelectric device is applied across the capacitive structure connected to the triboelectric device, wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes.
  • a modulated optical signal is generated responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device using an optical source coupled to the optical modulator.
  • the generated modulation signals or sensor signals may be used for one or more of a group consisting of wireless control/communication, healthcare monitoring, and human machine interface applications.
  • the method may comprise using one or more triboelectric devices to generate output voltage spikes responsive to a force being applied thereto.
  • the method may comprise using a plurality of capacitive structures, each of the plurality of capacitive structures comprising a corresponding optical modulator disposed between opposing electrodes, to generate a modulated optical signal responsive to the output voltage from a corresponding triboelectric device and hence the force applied to the corresponding triboelectric device.
  • FIG. 23 shows a flowchart 2300 illustrating a method of fabricating an integrated system, according to an example embodiment.
  • a triboelectric device is provided configured for generating a voltage output responsive to a force being applied to the triboelectric device.
  • a capacitive structure is provided and connected to the triboelectric device for applying the voltage output from the triboelectric device across the capacitive structure; wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and wherein the optical modulator is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device.
  • the optical modulator may comprise a microring resonator.
  • the optical modulator may comprise a Mach-Zehnder interferometer.
  • the triboelectric device may be textile based.
  • the triboelectric device may comprise material layers disposed on opposite sides of a flexible spacer structure.
  • the method may comprise providing a plurality of triboelectric devices including the triboelectric device configured for generating the voltage output responsive to the force being applied thereto.
  • One or more of the plurality of triboelectric devices may be configured for generating output voltage spikes responsive to a force being applied thereto.
  • the method may comprise providing a micro controller unit directly connected to the one or more triboelectric devices configured for generating output voltage spikes responsive to the force being applied thereto.
  • the method may comprise providing a photodetector, wherein the micro controller is configured to receive the modulated optical signal via a photodetector.
  • the method may comprise providing a plurality of capacitive structures, each of the plurality of capacitive structures comprising a corresponding optical modulator disposed between opposing electrodes, and each of the plurality of capacitive structures being connected to a corresponding one of the plurality of triboelectric devices for applying the voltage output from the corresponding triboelectric device across said each capacitive structure, wherein each of the optical modulators is configured to generate a modulated optical signal responsive to the output voltage from the corresponding triboelectric device and hence the force applied to the corresponding triboelectric device.
  • the method may comprise providing a glove as carrier of the plurality of triboelectric devices.
  • PLDs programmable logic devices
  • FPGAs field programmable gate arrays
  • PAL programmable array logic
  • ASICs application specific integrated circuits
  • microcontrollers with memory such as electronically erasable programmable read only memory (EEPROM)
  • EEPROM electronically erasable programmable read only memory
  • embedded microprocessors firmware, software, etc.
  • aspects of the system may be embodied in microprocessors having software -based circuit emulation, discrete logic (sequential and combinatorial), custom devices, fuzzy (neural) logic, quantum devices, and hybrids of any of the above device types.
  • the underlying device technologies may be provided in a variety of component types, e.g., metal-oxide semiconductor field-effect transistor (MOSFET) technologies like complementary metal-oxide semiconductor (CMOS), bipolar technologies like emitter- coupled logic (ECL), polymer technologies (e.g., silicon-conjugated polymer and metal- conjugated polymer-metal structures), mixed analog and digital, etc.
  • MOSFET metal-oxide semiconductor field-effect transistor
  • CMOS complementary metal-oxide semiconductor
  • ECL emitter- coupled logic
  • polymer technologies e.g., silicon-conjugated polymer and metal- conjugated polymer-metal structures
  • mixed analog and digital etc.

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Abstract

An integrated system, a method of generating modulation signals or sensor signals, and a method of fabricating an integrated system. The integrated system comprises a triboelectric device configured for generating a voltage output responsive to a force being applied to the triboelectric device; and a capacitive structure connected to the triboelectric device for applying the voltage output from the triboelectric device across the capacitive structure; wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and wherein the optical modulator is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device.

Description

INTEGRATED SYSTEM FOR SELF-SUSTAINABLE PHOTONIC MODULATION AND
CONTINUOUS FORCE SENSING
FIELD OF INVENTION
The present invention relates broadly to an integrated system, to a method of generating modulation signals or sensor signals using the integrated system, and to a method of fabricating an integrated system, and in particular to a wearable triboelectric nano-energy-nano-system with self-sustainable photonic modulation and continuous force sensing.
BACKGROUND
Any mention and/or discussion of prior art throughout the specification should not be considered, in any way, as an admission that this prior art is well known or forms part of common general knowledge in the field.
Wearable electronics has rapidly advanced over the past decade to push the boundary of sensor technology towards conformal, flexible, and stretchable sensors for personalized healthcare [1- 3], smart displays [4-6], robotics [7,8], and Internet-of-Things (IoT) [9,10] applications. Several transducing mechanisms have been investigated, including resistive [11], capacitive [12], thermoelectric [13,14], piezoelectric [15-17], triboelectric [18-20], and hybrid transducing mechanisms [21,22]. Among these mechanisms, the piezoelectric and triboelectric transducing mechanisms are promising in realizing self-sustainable wearable electronic sensors to improve the convenience, wearing comfort, and to reduce the overall power consumption of sensing systems [23-28]. In particular, triboelectric sensors (TESs) have been considered as superior candidates for self-sustainable wearable electronic sensors because of their flexibility [29-31], versatile operation modes [32,33], broad material availability [34-38], low cost [39- 41], and good scalability [42-44].
Since the conception of triboelectric devices, research efforts have been mainly focused on the material and architecture optimization to increase the energy harvesting efficiency of triboelectric nanogenerators [45-47]. Recently, research interests gradually migrate to three major aspects, namely self-sustainable TESs for IoT applications [27,48], triboelectric materials with novel functionalities [49,50], and TES-based human-machine-interface (HMI) for robotic control and virtual/augmented reality (VR/AR) interactions [51-53].
Nonetheless, a major restriction of TESs is their pulse-like signals which are unstable and even cause stimuli information loss [54,55] . The pulse-like signal is a practical limitation when TESs are connected to external circuits. Due to the transient current flow upon the electrostatic induction process, the TES’s electrical states determined by different stimuli shift rapidly to the electrical equilibrium, resulting in only a sharp pulse-like signal received by the external readout circuit with significant information loss. One solution is to use a high impedance readout circuit to suppress current flows as well as the corresponding electrical state shifts [56,57.] Yet, an amplifying circuit is required to read the small current information, complicating the sensing system. Another solution involves the utilization of deep learning techniques [58-60]. By training the deep neural network (DNN) with abundant data, the DNN can extract the major features of the pulse-like signal and make correct decisions even in the presence of information loss. Nonetheless, the deep learning techniques require massive training data and can only make final decisions at the expense of ignoring intermediate states.
On top of wearable electronics, wearable photonics has been developed as a complementary technology for radio-frequency interference (RFI) free sensors [61-63], optogenetics [64,65], photomedicine [66], and high-speed transmission [67]. Several wearable photonic building blocks have been investigated including flexible waveguides [68-70], flexible light-emitting devices [71] and lasers [72,73], and flexible photodetectors [74,75]. The applications of triboelectric technology in nanophotonics have also enabled novel photodetection [76-78] and photoluminescence platforms [79-81]. However, how nanophotonics can help triboelectric technology has rarely been reported.
Conventional photonic modulators are typically realized by silicon photonics and rely on the thermo-optic effect and the free carrier dispersion effect. With these two types of current-based modulation mechanisms, the power consumption of photonic modulators increases drastically when there are a few photonic modulators deployed in e.g. wearable systems in order to realize system-level features, for example, computation and tunable (de)multiplexing. Self-sustainable devices with longer lifespan and lightweight are desirable for convenience and wearing comfort. On the other hand, triboelectric technology stands out as a promising versatile technology due to its flexibility, self-sustainability, broad material availability, low-cost, and good scalability. Nevertheless, when connecting to an external electrical circuit in practical applications, TENG sensors’ electrical state determined by different stimuli shifts transiently to the electrical equilibrium, producing an unstable pulse-like signal with significant loss of stimuli information.
Embodiments of the present invention seek to address at least one of the above problems.
SUMMARY
In accordance with a first aspect of the present invention, there is provided an integrated system comprising: a triboelectric device configured for generating a voltage output responsive to a force being applied to the triboelectric device; and a capacitive structure connected to the triboelectric device for applying the voltage output from the triboelectric device across the capacitive structure; wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and wherein the optical modulator is coupled to an optical source and is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device.
In accordance with a second aspect of the present invention there is provided a method of generating modulation signals or sensor signals comprising the steps of: generating a voltage output responsive to a force being applied to a triboelectric device; applying the voltage output from the triboelectric device across the capacitive structure connected to the triboelectric device, wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and generating a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device using an optical source coupled to the optical modulator.
In accordance with a third aspect of the present invention there is provided a method of fabricating an integrated system comprising: providing a triboelectric device configured for generating a voltage output responsive to a force being applied to the triboelectric device; and providing a capacitive structure connected to the triboelectric device for applying the voltage output from the triboelectric device across the capacitive structure; wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and wherein the optical modulator is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings, in which:
Figure 1 shows a diagram illustrating a wearable NENS according to an example embodiment comprised of a tiny rigid AIN photonic module and a T-TES module serving as a high voltage source. Figure 2(a)(i) shows the equivalent circuit model diagram of a wearable NENS according to an example embodiment.
Figure 2(a)(ii) shows diagrams illustrating the fundamental working principle of the integrated system according to an example embodiment.
Figure 2(a)(iii) shows diagrams illustrating the fundamental working principle of the integrated system according to an example embodiment.
Figure 2(b)(i) shows an optical image of a textile TES (T-TES) for use in an example embodiment.
Figure 2(b)(ii) shows a scanning electron microscope (SEM) image of a conductive textile for use in an example embodiment.
Figure 2(b)(iii) shows an optical image of the AIN modulator for use in an example embodiment.
Figure 2(b)(iv) shows a tunneling electron microscope (TEM) image of the AIN modulator for use in an example embodiment.
Figure 3(a) shows the T-TES open-circuit voltage under different applied periodic force, for use in an example embodiment.
Figure 3(b) shows the T-TES short-circuit current under different applied periodic forces, for use in an example embodiment.
Figure 3(c) shows the dependence of open-circuit Vpp on the impact force magnitude, for use in an example embodiment.
Figure 3(d) shows the load cell speed dependence of open-circuit Vpp under constant impact force magnitude at 200 N, for use in an example embodiment.
Figure 3(e) shows output voltage and output power of the T-TES module at different load resistances, for use in an example embodiment.
Figure 3(f) shows a contour map showing the dependence of open-circuit Vpp on impact force magnitude and contact area, for use in an example embodiment.
Figure 3(g)shows a schematic of the AIN MRR for use in an example embodiment.
Figure 3(h) shows the resonance characteristics of the AIN MRR with fixed g but varying R, for use in an example embodiment.
Figure 3(i) shows the resonance characteristics of AIN MRR with fixed R but varying g, for use in an example embodiment.
Figure 4(a) shows the transmission spectrum of the AIN MRR (R = 50 pm, g = 0.55 pm) in 1510 nm to 1570 nm, for use in an example embodiment. Figure 4(b) shows a zoom-in spectrum to the resonant wavelength at 1555.525 nm, for use in an example embodiment.
Figure 4(c) shows that the DC tuning of the resonant wavelengths in different AIN MRRs, for use in example embodiment.
Figure 4(d) shows the coupling gap dependence of the DC tuning efficiency, for use in an example embodiment.
Figure 4(e) shows the Radius dependence of the DC tuning efficiency, for use in an example embodiment.
Figure 4(f) shows the AC modulation of the AIN modulator at 100 MHz, for use in an example embodiment.
Figure 4(g) shows the AC modulation of the AIN modulator at 3 GHz, for use in an example embodiment.
Figure 4(h) shows the accumulated modulation signals at 3, 4, and 5 GHz, for use in an example embodiment.
Figure 5(a) shows an image of a spacer TES (S-TES) for use in an example embodiment.
Figure 5(b) shows an image of a smart glove with a textile TES (T-TES) for use in an example embodiment.
Figure 5(c) shows an image of a short AIN MZI modulator for use in an example embodiment.
Figure 5(d) shows an image of a long AIN MZI modulator for use in an example embodiment.
Figure 5(e) shows a tunneling electron microscope (TEM) image of the tunable aluminum nitride (AIN) waveguide’s cross-section, for use in an example embodiment.
Figure 6(a) shows the S-TES is composed of a negative triboelectric part of PTFE/Al/foam/PET (illustrated in part in an exploded view) and a positive triboelectric part of Al/foam/PET, with a sponge spacer in between, for use in an example embodiment.
Figure 6(b) shows the measured Voc of the S-TES under different Fs of 18 N, 52 N, 80 N and 170 N (at a constant VF of 100 mm/min), for use in an example embodiment.
Figure 6(c) shows the output voltage (V) and power (P) performance of the S-TES at different external resistances (R’), with F of 170 N and VF of 100 mm/min, for use in an example embodiment.
Figure 6(d) shows Voc of S-TES according to an example embodiment rapidly increases from 19 V at 10 N to 81 V at 30 N, then slowly rises to 92 V at 60 N, and saturates thereafter (> 60 N). Figure 6(e) shows Voc of S-TES according to an example embodiment is not affected by VF from 100 mm/min to 500 mm/min as implied by the near-zero linearly fitted slope, showing good stability across different VFS.
Figure 6(f) shows Voc of S-TES according to an example embodiment can practically respond exactly to the force profile induced by hand control, fully reflecting the force information.
Figure 6(g) shows a textile TES for use in an example embodiment.
Figure 6(h) shows the testing results of the T-TES 502 under different Fs of 10 N, 40 N, 80 N, and 170 N (at a constant VF of 100 mm/min), for use in an example embodiment.
Figure 6(i) shows the V and P performance of the T-TES at different R’s, for use in an example embodiment.
Figure 6(j) shows that Voc of the T-TES gradually increases from 45 V at 10 N to 77 V at 115 N, after which Voc becomes relatively stable, for use in an example embodiment.
Figure 6(k) shows the effect of different VFS, V0C of the T-TES is also consistent under different VFS from 100 mm/min to 500-mm/min, for use in an example embodiment.
Figure 6(1) shows the Voc profile generated by human hand control of the T-TES 502, for use in an example embodiment.
Figure 7(a) shows the short AIN MZI modulator with the arm length of Larm = 2.16 mm occupies a footprint of only 0.81 mm2, for use in an example embodiment.
Figure 7(b) shows a free-spectral range (FSR) of 5.81 nm in the telecommunication wavelength range of 1520 nm to 1600 nm for the short AIN MZI modulator, for use in an example embodiment.
Figure 7(c) shows the zoom-in wavelength spectrum in Figure 7(c) showing a sine fit with an R-square of 0.98.
Figure 7(d) shows the schematic of the long AIN MZI modulator with Larm = 28.06 mm and a footprint of 1.38 mm2, for use in an example embodiment.
Figure 7(e) shows an FSR of 7.14 nm of the long AIN MZI modulator, for use in an example embodiment.
Figure 7(f) shows the zoom-in wavelength spectrum in Figure 7(e) showing a sine fit with an R-square of 0.99.
Figure 7(g) shows the direct current (DC) tuning characteristics of the short AIN MZI modulator, for use in an example embodiment.
Figure 7(h) shows the direct current (DC) tuning characteristics of the long AIN MZI modulator, for use in an example embodiment. Figure 7(i) shows the dependence of the phase change on V for the short and long AIN MZI modulator, for use in an example embodiment.
Figure 7(j) shows the T - V curve for the short and long AIN MZI modulator, for use in an example embodiment.
Figure 8(a) shows the temporal spectrum of normalized T in the short AIN MZI modulator under 10 kHz AC modulation signal with different magnitudes, for use in an example embodiment.
Figure 8(b) shows the temporal spectrum of normalized T in the short AIN MZI modulator under 10 kHz AC modulation signal with different magnitudes, for use in an example embodiment.
Figure 8(c) shows the quantitative relation between normalized tuning and Vpp, for use in an example embodiment.
Figure 8(d) shows the temporal T response of the short MZI under 100-kHz AC modulation, for use in an example embodiment.
Figure 8(e) shows the temporal T response of the long MZI under 100-kHz AC modulation, for use in an example embodiment.
Figure 8(f) shows the measured results indicate a 3-dB bandwidth of 0.9 MHz in the long AIN MZI modulator 503 and 1.1 MHz in the short AIN MZI modulator, for use in an example embodiment.
Figure 8(g) shows that when a voltage pulse that sharply rises from 0 V to [27 x N] V is applied to the long MZI, where N is an integer ranging from 1 to 7, it is observed that N peak and troughs appear in the temporal T spectrum when [27 x N] V is applied, and T finally reaches the same level as T at 0 V, for use in an example embodiment.
Figure 9(a)shows the impact force magnitude dependence of Vpp applied on the AIN MRR and the corresponding resonant wavelength shift, for use in an example embodiment.
Figure 9(b) shows the load cell speed dependence of Vpp applied on the AIN MRR and the corresponding resonant wavelength shift, for use in an example embodiment.
Figure 9(c) shows a contour map showing the dependence of resonant wavelength shift on impact force magnitude and contact area, for use in an example embodiment.
Figure 9(d) shows the T-TES output voltage waveform generated by periodic motion of the force gauge and the characteristic T-TES stages in terms of contact/separation mode, according to an example embodiment.
Figure 9(e) shows the resonance wavelength shift induced by T-TES voltage output and the corresponding optical transmission waveform at the operation wavelength of 1555.455 nm, according to an example embodiment. Figure 9(f) shows the resonance wavelength shift induced by T-TES voltage output and the corresponding optical transmission waveform at the operation wavelength of 1555.48 nm, according to an example embodiment.
Figures 9(g) shows the resonance wavelength shift induced by T-TES voltage output and the corresponding optical transmission waveform at the operation wavelength of 1555.525 nm, according to an example embodiment.
Figure 9(h) shows the resonance wavelength shift induced by T-TES voltage output and the corresponding optical transmission waveform at the operation wavelength of 1555.531 nm, according to an example embodiment.
Figure 9(i) shows the resonance wavelength shift induced by T-TES voltage output and the corresponding optical transmission waveform at the operation wavelength of 1555.555 nm, according to an example embodiment.
Figure 10(a) shows the impact force magnitude, the resultant applied voltage on the AIN modulator, together with the optical transmission spectrum at different load cell speeds of 900 mm/min, (b) 700 mm/min, and (c) 500 mm/min in a NENS according to an example embodiment.
Figure 10(b) shows the impact force magnitude, the resultant applied voltage on the AIN modulator, together with the optical transmission spectrum at different load cell speeds of 700 mm/min, in a NENS according to an example embodiment.
Figure 10(c) shows the impact force magnitude, the resultant applied voltage on the AIN modulator, together with the optical transmission spectrum at different load cell speeds of 500 mm/min in a NENS according to an example embodiment.
Figure 10(d) shows zoom-in of the spectra in Figures 10(a) to a complete operation cycle.
Figure 10(e) show zoom-in of the spectra in Figures 10(b) to a complete operation cycle.
Figures 10(f) show zoom-in of the spectra in Figures 10(c) to a complete operation cycle.
Figure 10 (g) shows a calibration curve showing the one-to-one correspondence of the optical transmission and the impact force magnitude at different load cell speeds, according to an example embodiment.
Figure 10(h) shows the proposed physical model that describes the integrated system according to an example embodiment.
Figure 11(a) shows S-TES’s output voltage (VS-TES) under different Fs at 100 mm/minm according to an example embodiment.
Figure 11(b) shows the VF dependence of VS-TES and the corresponding resultant T according to an example embodiment. Figure 11(c) shows one force cycle divided into four regions as illustrated by the differently shaded areas, according to an example embodiment.
Figure 11(d) shows the corresponding electrostatically induced VS-TES, according to an example embodiment.
Figure 11(e) shows three critical force states are labeled by (T), (2), and (3) respectively, according to n example embodiment.
Figure 11(f) shows the temporal T spectrum, according to an example embodiment.
Figure 11(g) shows the detailed temporal F-VS-TES-T spectra in 11 - 14 s, according to an example embodiment.
Figure 11(h) shows the one-to-one corresponding data extracted from Figure 11(g) to derive the resultant relation between T and F in the S-TES, according to an example embodiment.
Figure 12 shows the measured and fitted relation between V and F with a one to one correspondence (data is extracted from Figure 11(g), according to an example embodiment.
Figure 13 shows the measured and fitted relation between T and F, according to an example embodiment.
Figure 14 shows that measured and fitted V-F relation, according to an example embodiment.
Figure 15 shows that measured and fitted T-F relation, according to an example embodiment.
Figure 16(a) shows T-TES’s output voltage (VS-TES) under different Fs at 100 mm/minm according to an example embodiment.
Figure 16(b) shows the VF dependence of VT-TES and the corresponding resultant T according to an example embodiment.
Figure 16(c) shows one force cycle divided into four regions as illustrated by the differently shaded areas, according to an example embodiment.
Figure 16(d) shows the corresponding electrostatically induced VT-TES, according to an example embodiment.
Figure 16(e) shows three critical force states are labeled by (T), (2), and (3) respectively, according to n example embodiment.
Figure 16(f) shows the temporal T spectrum, according to an example embodiment.
Figure 16(g) shows the detailed temporal F-VT-TES-T spectra in 11 - 14 s, according to an example embodiment.
Figure 16(h) shows the one-to-one corresponding data extracted from Figure 11(g) to derive the resultant relation between T and F in the T-TES, according to an example embodiment. Figure 17(a) shows the schematic of the measurement system for optical Morse code transmission, according to an example embodiment.
Figure 17(b) illustrates the custom-built software can translate the detected signal into the pre defined alphabets whose array could convey the desired messages, according to an example embodiment.
Figure 17(c) demonstrates the transmission of all the 26 alphabets, according to an example embodiment.
Figure 17(d) shows a message array conveying ‘HINUS’, according to an example embodiment.
Figure 17(e) shows a photo and graphs illustrating a monitoring scenario of continuous force when the textile wearable NENS is attached on a human arm, according to an example embodiment.
Figure 17(f) shows a photo and graphs illustrating a monitoring scenario of continuous force when the textile wearable NENS is attached on a human sole, according to an example embodiment.
Figures 18(a) shows a schematic illustration of the S-TES, for use in an example embodiment.
Figure 18(b) shows a schematic of the short AIN MZI modulator lwith an arm length (Larm) of 2.16 mm and footprint of 0.81 mm2, for use in an example embodiment.
Figure 18(c) shows the linear relation between Transmission and Force in the 35 - 60 N force range with a sensitivity of 0.659 mV/N, according to an example embodiment.
Figures 18(d) shows a schematic illustration of the elastic T-TES, for use in an example embodiment.
Figure 18(e) shows a schematic of the long AIN MZI modulator (Larm = 28.06 mm, footprint = 1.38 mm2), for use in an example embodiment.
Figure 18(f) shows the linear relation between Transmission and Force in the 7 - 70 N force range with a sensitivity of 0.174 mV/N, and 75 - 110 N force range with a sensitivity of - 0.793 mV/N, according to an example embodiment.
Figure 19(a) shows the schematic circuit diagram of a robotic hand control system according to an example embodiment.
Figure 19(b) shows the optical signal output of the thumb and the corresponding signals of the other fingers from the glove in the system of Figure 19(a), according to an example embodiment for controlling the finger number and the movement speed of the robotic hand.
Figure 20(a) shows screenshots of a flower planting process in the AR space, according to an example embodiment. Figure 20(b) shows the output signals of the fingers in the flower planting process, according to an example embodiment.
Figure 20(c) shows a screenshot of continuous showering the flower in the AR space, according to an example embodiment.
Figure 20(d) shows the curve of optical output in continuous showering step, according to an example embodiment.
Figure 21 shows a schematic drawings illustrating an integrated system according to an example embodiment.
Figure 22 shows a flowchart illustrating a method of generating modulation signals or sensor signals according to an example embodiment.
Figure 23 shows a flowchart illustrating a method of fabricating an integrated system, according to an example embodiment.
DETAILED DESCRIPTION
Wearable photonics offers a promising platform to complement the thriving complex wearable electronics system by providing high-speed data transmission channel and robust optical sensing path. Regarding the realization of photonic computation and tunable (de)multiplexing functions based on system-level integration of abundant photonic modulators, embodiments of the present invention address this issue by integrating a voltage-based aluminum nitride (AIN) modulator and textile triboelectric sensor (T-TES) on a wearable platform to form a nano- energy-nano- system (NENS). In example embodiments, the T-TES transduces the mechanical stimulations into electrical signals based on the coupling of triboelectrification and electrostatic induction. The self-generated high-voltage from the T-TES is applied to the AIN modulator and boosts its modulation efficiency regardless of AlN’s moderate Pockels effect. Complementarily, AIN modulator’s capacitive nature enables the open-circuit operation mode of T-TES, providing the integrated NENS according to example embodiment with continuous force sensing capability which is notably uninfluenced by operation speeds. With the enhanced photonic modulation and the open-circuit operation mode enabled by synergies between the AIN modulator and the T-TES according to example embodiments, optical Morse code transmission and continuous human motion monitoring are demonstrated. Leveraging the design flexibility of TENG and AIN nanophotonic circuits for force monitoring, various linear sensitivities independent of force speed can be achieved in different force ranges. Toward practical applications, a smart glove based on the NENS is provided according to an example embodiment to realize continuous real-time robotic hand control and virtual/augmented reality (VR/AR) interaction. Under the auspices of T-TES, the generated high voltage output, the excellent optical tuning feature, and the open-circuit operation mode of the wearable NENS according to embodiments of the present invention can pave the way to future self-sustainable wearable tunable photonics for communication, healthcare monitoring, and human-machine interface applications.
To the inventors’ knowledge, embodiments of the present invention provide the first implementation of integrating the two domains of technologies, namely TENG and AIN photonics. The synergy between triboelectric technology and AIN photonics according to example embodiments can offer extra benefits to both sides. The high-voltage from TENG can be applied to the AIN modulator with negligible degradation and effectively enhance the modulation efficiency through bypassing the limited tuning efficiency restricted by AlN’s moderate Pockets effect. Complementarity, the capacitor nature of AIN modulator and the optical transmission capability of photonic system could be another possible solution to continuously monitor the TENG output in a compact and easy-to-implement manner other than the conventional open-circuit voltage/charge approach which relies on bulky and complicated external electrical circuits.
In an example embodiment, integrating a TENG sensor with a micro parallel-plate capacitor sandwiching an aluminum nitride (AIN) nanophotonic waveguide enables the TENG sensor to work in the open-circuit condition with a negligible electrical state shift.
Embodiments of the present invention can benefit wearable self-sustainable electronics and photonics for applications ranging from human machine interface, smart home, robotics, and augmented reality / virtual reality interactions.
Concept of the Wearable Triboelectric- AIN NENS according to example embodiments
Figure 1 shows a diagram illustrating a wearable NENS 100 according to an example embodiment comprised of a tiny rigid AIN photonic module 102 and a T-TES module 104 serving as a high voltage source. Mechanical, electrical, and optical signals can be transduced in the system to achieve wide photonic modulation and continuous force sensing. The details of the AIN photonics module 102 and the exploded view of the T-TES 104 are presented. Examples of the potential applications of the system include, but are not limited to, wireless control/communication, healthcare monitoring, human machine interface. Figure 2(a)(i) shows the equivalent circuit model diagram and (ii & iii) show diagrams illustrating the fundamental working principle of the integrated system. Figure 2(b)(i) shows an optical image of the T-TES 104; Figure 2(b)(ii) shows a scanning electron microscope (SEM) image of a conductive textile; Figure 2(b)(iii) shows an optical image of the AIN modulator 102, and Figure 2(b)(iv) a tunneling electron microscope (TEM) image of the AIN modulator 102.
More specifically, the integration of aluminum nitride (AIN) modulator 102 and wearable textile triboelectric sensor (T-TES) 104 takes advantage of both devices and enables their synergy. The wearable triboelectric-AIN nano-energy-nano-system (NENS) 100 according to an example embodiment with self-sustainable photonic modulation and continuous force sensing functions features a wearable platform comprised of the tiny rigid AIN photonic module 102 and a T-TES module 104 as shown in Figure 1. As illustrated in the outer signal flow circle, fundamentally the self-sustainable photonic modulation is realized by using the T- TES 104 as a power supply. The T-TES 104 transduces the mechanical stimulations to electrical signals based on the coupling of triboelectrification and electrostatic induction. The self-generated electrical signals are then applied to the AIN modulator 102 to generate modulated optical signals, which are routed to photodetectors e.g. 108 and converted to electrical readouts. Complementarily, the continuous force sensing is realized by using the AIN modulator 102 for sensing signal readout. Such a readout scheme decouples the sensing path and the signal readout path so that high optical readout signals can be received even when the electrical sensing circuit is operated with low output current.. The AIN modulator 102 is composed of an AIN microring resonator (MRR) 110 sandwiched by a pair of top and bottom electrodes 112, 114 to leverage AlN’s rl3 electro-optic (EO) coefficient. The electrodes 112, 114 are connected to the T-TES 104 output. As for the T-TES module 104, flexible Ecoflex and nitrile layers on conductive textiles are adopted as the negative and positive friction surface respectively. Upon physical contact, opposite charges with equal quantity are generated on the two surfaces due to their different electron affinities. Upon separation of the two charged surfaces, the built-up electric potential difference will induce an output voltage in the external circuit. A thin spacer is sandwiched between two functional layers for separation. The entire structure is encapsulated by two additional pieces of non-conductive textiles.
Figure 2(a) explains the basic working mechanism of the system 100 according to an example embodiment. In the equivalent circuit model diagram (Figure 2(a)(i)), the T-TES 104 can be considered as a serial connection of an alternating current (AC) voltage source and a capacitor, while the AIN modulator 102 acts as a parallel plate capacitor. The AIN MRR 110 is initially working on resonance where the optical transmission is zero at the output 116 (Figure 2(a)(ii)). Zero-bias is applied to the AIN MRR 110 when the T-TES 104 is in the contact mode since opposite charges are neutralized at the contact interface. Contrarily, a high-voltage is applied to the AIN MRR 110 when the T-TES 104 is in the separation mode due to electrostatic induction. The generated strong electric field (E-field) alters AlN’s refractive index through Pockels effect and consequently changes the resonant condition. The AIN MRR 110 then operates in the off-resonance condition, and measurable optical transmission is received at the output 116 (Figure 2(a)(iii)). The intensity of the optical transmission depends on the voltage from the T-TES 104. Figure 2(b) shows an optical image of the wearable T-TES 104 (Figure 2(b)(i)), the SEM image of a top view of the conductive (Figure 2(b)(ii)), the optical image of the AIN modulator 102 (Figure 2(b)(iii)) as well as its tunneling electron microscope (TEM) image (Figure 2(b)(iv)) of a perspective view from one side.
The conversion between physical quantities and the related physical effects enable the information flow in an integrated triboelectric sensor (TES)/nanophotonics sensing system according to an example embodiment. The human inputs a force signal (F), causing a mechanical deformation (Ax) in the TES according to the stress-strain relation. The mechanical deformation is transduced to an electrical signal (V) through the triboelectrification and electrostatic induction process. The electrical signal is then applied to the nanophotonic readout circuit and transduced into a photonic signal (T) by the electro-optic Pockels effect. The photonic signal is finally read out for e.g. robotic control and VR/AR interactions. Characterization of the T-TES and the AIN Modulator according to example embodiments
Figure 3(a) shows the T-TES open-circuit voltage under different applied periodic force. Figure 3(b) shows the T-TES short-circuit current under different applied periodic forces. Figure 3(c) shows the dependence of open-circuit Vpp on the impact force magnitude. Figure 3(d) shows the load cell speed dependence of open-circuit Vpp under constant impact force magnitude at 200 N. Figure 3(e) shows output voltage and output power of the T-TES module 104 at different load resistances. Figure 3(f) shows a contour map showing the dependence of open- circuit Vpp on impact force magnitude and contact area. Figure 3(g)shows a schematic of the AIN MRR. Figure 3(h) shows the resonance characteristics of the AIN MRR with fixed g but varying R. Figure 3(i) shows the resonance characteristics of AIN MRR with fixed R but varying g.
The fabricated T-TES generates sufficient voltage and power to enable enhanced photonic modulation and even sustain the entire wearable NENS according to an example embodiment. The basic characterization of the T-TES is first conducted using a force gauge testing system that provides impact forces with controllable magnitudes by a load cell with varying speeds. Figure 3(a) shows the typical open-circuit voltage waveforms of the T-TES under different impact force magnitudes of 41 N, 77 N, and 197 N, respectively (at 900 mm/min load cell speed). Clear improvement of the open-circuit voltage along with the increasing impact force magnitude can be observed. The short-circuit current of the T-TES under the same impact force magnitudes is presented in Figure 3(b), exhibiting the same improvement trend. The detailed relationship of the open-circuit voltage (peak to peak value Vpp) and the impact force magnitude is plotted in Figure 3(c), at 900 mm/min load cell speed. It is observed that Vpp increases rapidly and linearly in the low impact force magnitude range, and then gradually saturates in the higher impact force magnitude range. A maximum Vpp of 350 V can be achieved under 600 N force. The Vpp increment is associated with the larger amount of charges generated due to stronger material surface interaction under higher impact force magnitude. Besides the impact force magnitude, the load cell speed is a critical parameter when the T-TES is used in practical applications. Thus, the relationship between Vpp and the load cell speed (at 200 N force) is also investigated and shown in Figure 3(d). As expected, highly stable Vpp are observed at various speeds as a result of T-TES ’s open-circuit operation mode, demonstrating that the Vpp of T-TES is only determined by the impact force magnitude but independent of the load cell speed in open-circuit operation mode. To examine the power generation capability of the T-TES, Vpp from different resistor loads when they are connected to the T-TES (at 200 N force) are measured. The corresponding output power is then calculated by P=V2/R and plotted in Figure 3(e). A maximum output power of 64 pW can be achieved when the connected resistor load is 33 MW. Towards practical wearable applications, the output performance of the T-TES is also measured by finger tapping in the scenarios of using one, two and three fingers. The resultant Vpp under various impact force magnitudes and contact areas (different number of fingers) is presented in Figure 3(f), showing an apparent increment of Vpp with both larger impact force magnitudes and contact areas. Therefore, output voltage with adjustable magnitudes can be easily achieved by controllable human tapping in order to realize targeted photonic modulation applications, according to example embodiments.
A high-performance AIN modulator is used for high-speed optical transmission, on-chip computation, and effective tuning in a system according to an example embodiment. In order to systematically characterize the AIN modulator, an array of AIN modulators is fabricated. The characteristic of the AIN modulator is fundamentally determined by the ring radius (R) and coupling gaps (g) of the AIN MRR 300 (Figure 3(g)). According to the resonant condition of MRR, the resonant wavelength lk is solely determined by R. Thus, by varying R, lk can be designed to operate at specific wavelengths. The free spectral range (FSR) associated with the spacing between different RS will change with R as well. The spectra of the AIN MRRs with fixed g = 0.5 pm and different Rs are plotted in Figure 3(h) while the corresponding measured lk around 1555 nm and FSR are presented in Table SI.
Table SI . The l{( and FSR of AIN microring resonators with varying radius
Figure imgf000017_0001
lk is positively related to R while the FSR decreases with an increasing R. The resonant lineshape can be effectively tailored by varying g. As shown in Figure 3(i), when R is fixed at 30 pm, by increasing g from 0.35 pm to 0.60 pm in step of 0.05 pm, lk remains constant at 1554.429 ± 0.033 nm. The expected lk is substantially insensitive to the change in g. However, Figure 3(i) also indicates that the quality factor (Q factor) and the extinction ratio (ER) are strongly dependent on the coupling gap. The Q factor can be superior to 100 K at the under coupling condition while the ER can reach a maximum of 15.8 dB at critical-coupling conditions.
Figure 4(a) shows the transmission spectrum of the AIN MRR (R = 50 pm, g = 0.55 pm) in 1510 nm to 1570 nm. Figure 4(b) shows a zoom-in spectrum to the resonant wavelength at 1555.525 nm. Figure 4(c) shows that the DC tuning of the resonant wavelengths in different AIN MRRs. Figure 4(d) shows the coupling gap dependence of the DC tuning efficiency. Figure 4(e) shows the Radius dependence of the DC tuning efficiency. Figure 4(f) shows the AC modulation of the AIN modulator at 100 MHz. Figure 4(g) shows the AC modulation of the AIN modulator at 3 GHz. Figure 4(h) shows the accumulated modulation signals at 3, 4, and 5 GHz.
More specifically, an AIN MRR with R = 50 pm and g = 0.55 pm is firstly used to characterize the modulation performance of the AIN modulator in a system according to an example embodiment. The optical transmission spectrum of the AIN MRR around the telecommunication C-Band is presented in Figure 4(a). An average insertion loss of 5.73 dB and a free spectral range (FSR) of 3.612 nm is demonstrated. Figure 4(b) zooms into the resonant wavelength at 1555.525 nm, revealing a 3-dB bandwidth of 34 pm which corresponds to Q factor of 45,750. An ER of 21.5 dB is accompanied. Next, the performance of the AIN modulator according to an example embodiment under different applied biases is investigated. The direct current (DC) tuning result is plotted in Figure 4(c). In two individual AIN modulators with (R = 30 pm, g = 0.55 pm) and (R = 100 pm, g = 0.55 pm), the resonant wavelength can be continuously tuned in the range from 1553.366 nm to 1553.523 nm and 1553.551 nm to 1553.706 nm respectively when a -200 - 200 V DC bias is applied. A linear relationship between AR and the applied voltage is observed with a tuning efficiency of 0.39 pm/V. To further understand the influence of the undesired but inevitable fabrication variations on the tuning efficiency, the dependence of tuning efficiency on R and g is investigated. As shown in Figure 4(d), in AIN modulators with R = 50 pm but different gs, AR shifts 157.67 ± 2.08 pm when a 400 V bias difference is introduced. As for AIN modulators with g = 0.55 pm but different Rs, Figure 4(e) shows a AR shift (AAR) of 155.67 ± 1.15 pm under a 400 V bias difference. The results from Figure 4(d) and Figure 4(e) together indicate the tuning efficiency of AIN modulators is substantially robust and unaffected by the varying Rs and gs.
The high-speed modulation capability of the AIN modulator is investigated by applying square waves with 10 Vpp and + 5 V bias. To achieve the highest extinction ratio, ER, the device is working at 1555.525 nm which is the resonant wavelength that results in zero transmission without applying bias. As shown in Figure 4(f), the modulation is efficient at 100 MHz modulation frequency. There is a negligible phase delay between the input radio frequency (RF) clock signal and the modulated optical signal. The lowest and highest optical transmission is 3.7 mV and 32.4 mV respectively, corresponding to an ER of 9.4 dB. Figure 4(g) plots the modulation results at 3 GHz. Since the RF source has a maximum speed of 12.5 GHz, some RF signal distortions away from a square waveform are observed at 3 GHz in the clock signal. The AIN modulator still carries the input RF signal efficiently despite some small phase delays and a reduced ER of 2.12 dB. The rise time t,- and fall time rr (defined by 10 % and 90 % of the step height) is 60 ps and 80 ps respectively. A rough estimation of the cut-off frequency can be calculated as 2 GHz by:
Figure imgf000018_0001
The cut-off frequency is further verified by the optical transmission signal accumulated temporally as shown in Figure 4(h). The light is effectively modulated by the 3 GHz RF input. At 4 GHz, severe waveform distortion happens. And the AIN modulator fails to carry the RF signal at 5 GHz. In order to figure out the limiting factor of the maximum 3 GHz modulation speed, the photon lifetime rp in the MRR is estimated according to: z)=2p*ί*tr (2) where Q is the Q factor of the ring resonator, f is the light frequency. tr of around 40 ps is estimated, which is close to the measured rise time and fall time. Thus, it is believed that the limiting factor in the AIN modulator is the long photon lifetime. In order to increase the modulation speed, a modulator with a lower Q factor can be designed to reduce tr. With a moderate Q factor of 4000, the theoretical modulation speed limited by the photon lifetime can reach 20 GHz. Meanwhile, the top and bottom electrodes (compare numerals 112, 114 in Figure 1) design also needs careful consideration to ensure low RC delay for use in example embodiments, as will be appreciated by a person skilled in the art.
To cover different application aspects in wearable electronics, different force sensing ranges are required. Accordingly, two integrated TES/nanophotonics sensing systems according to example embodiments are developed for force monitoring in different ranges. One system according to an example embodiment has a spacer TES (S-TES) 500 (Figure 5(a)) integrated with a short AIN MZI modulator 501 (Figure 5(c)). The other one has a textile TES (T-TES) 502 (Figure 5(b)) integrated with a long AIN MZI modulator 503 (Figure 5(d)). The images of the four actual devices for the two integrated systems are shown in Figures 5(a) to (d), and the characteristics of them are investigated individually in Figures 6 and 7. A tunneling electron microscope (TEM) image of the tunable aluminum nitride (AIN) waveguide’s cross-section is shown in Figure 5(e), showing the waveguide is sandwiched by a pair of top and bottom electrodes.
As indicated in Figure 6(a), the S-TES 500 is composed of a negative triboelectric part of PTFE/Al/foam/PET (illustrated in part in an exploded view in Figure 6(a) and a positive triboelectric part of Al/foam/PET, with a sponge spacer in between. After fabrication, the S- TES 500 is tested using a force gauge testing system that applies forces with controllable magnitudes (F) and speeds (VF). The measured Voc of S-TES 500 under different Fs of 18 N, 52 N, 80 N and 170 N (at a constant VF of 100 mm/min) are shown in Figure 6(b), where Voc is positively related to F. The output voltage (V) and power (P) performance of the S-TES 500 at different external resistances (R’) is also measured (Figure 6(c)), with F of 170 N and VF of 100 mm/min.
According to the fitting curve, it can be observed that while V keeps increasing, P first increases and then decreases with R’, exhibiting the maximum value of 26.3 pW at a matched R’ of 57.3 MOhm. The detailed force response of Voc is characterized under different Fs and VFS. From Figure 6(d), Voc of S-TES 500 rapidly increases from 19 V at 10 N to 81 V at 30 N, then slowly rises to 92 V at 60 N, and saturates thereafter (> 60 N). On the other hand, Voc is not affected by VF from 100 mm/min to 500 mm/min as implied by the near-zero linearly fitted slope, showing good stability across different VFS (Figure 6(e)). Since Voc is solely determined by F and independent of VF, it can be adopted as the output indicator for real-time force monitoring. As further illustrated in Figure 6(f), Voc can practically respond exactly to the force profile induced by hand control, fully reflecting the force information. It is also noteworthy that Voc can be maintained at different levels, which is an important characteristic of TESs 500 working in the open-circuit condition. In addition to the S-TES 500, another TES fabricated by textile materials, i.e., textile TES (T- TES) 502, is developed for use in example embodiments to achieve a larger force monitoring range (Figure 6(g)). The T-TES 502 is composed of a negative eco-flex coated conductive carbon cloth, a narrow-gap spacer, a positive nitrile layer with another carbon cloth, encapsulated by two pieces of non-conductive textiles for electrical insulation. The testing results of the T-TES 502 under different Fs of 10 N, 40 N, 80 N, and 170 N (at a constant VF of 100 mm/min) are illustrated in Figure 6(h), indicating a positive relation between Voc and F as well. Based on the V and P performance of the T-TES 502 at different R’s (Figure 6(i)), the maximum P of 1.97 pW can be achieved at a matched R’ of 65.4 MOhm. As shown in Figure 6(j), Voc of the T-TES 502 gradually increases from 45 V at 10 N to 77 V at 115 N, after which Voc becomes relatively stable. Compared with the S-TES 500, the force sensitive range is extended from 60 N to 115 N, but V and P are both smaller. In terms of the effect of different VFS, VOC of T-TES 502 is also consistent under different VFS from 100 mm/min to 500-mm/min (Figure 6(k)). According to the Voc profile generated by human hand control as shown in Figure 6(1), it is confirmed that V0c can be precisely controlled when the T-TES 502 works in the open- circuit condition.
The TES 500/502 can be regarded as a voltage source V with an internal resistance R0 while the external resistance is R’. The output power of the TES (P) is:
Figure imgf000020_0001
Equation S 1
In the power curve presented in Figure 6(c) and Figure 6(i), the x-axis and y-axis are R’ and P respectively. Thus, fitting Figure 6(c) and Figure 6(i) using Equation SI, V and Ro as fitting parameters can be obtained. For the spacer triboelectric sensor (S-TES) 500 and the textile trriboelectric sensor (T-TES) 502, the fitted curves are represented by PS-TES = (77.6 / (57.3 + R’))2 x R’ and PT-TEs = (22.7 / (65.4 + R’))2 x R’, respectively.
AIN MZI modulators 501, 503 are characterized to ensure that they can carry the TES s’ 500, 502 voltage signals effectively. A short and a long AIN MZI modulator 501, 503 are designed to integrate with the S-TES 500 and the T-TES 502, respectively, according to example embodiments. Although the T-TES’s 502 saturation force is larger, its V0c is lower. Thus, a longer AIN MZI modulator 503 is used to provide a strong electric-field (E-field) / light interaction for maintaining a high nanophotonic readout resolution. The short AIN MZI modulator 501 with the arm length of Larm = 2.16 mm occupies a footprint of only 0.81 mm2 (Figure 7(a)). A free-spectral range (FSR) of 5.81 nm in the telecommunication wavelength range of 1520 nm to 1600 nm is presented in Figure 7(b). The zoom-in wavelength spectrum in Figure 7(c) shows a sine fit with an R-square of 0.98, illustrating the high quality of the short AIN MZI modulator 501 whose optical transmission (T) is theoretically governed by interference. Correspondingly, the schematic of the long AIN MZI modulator 503 with Larm = 28.06 mm and a footprint of 1.38 mm2 is shown in Figure 7(d), while an FSR of 7.14 nm and a sine fit with an R-square of 0.99 are presented in Figure 7(e) and Figure 7(f), respectively, for the long AIN MZI modulator 503. Next, the direct current (DC) tuning characteristics of both AIN MZI modulators 501, 503 are investigated. When the voltage bias (V) applied on the MZI modulator increases from - 200 V to 200 V, a constructive interference peak shifts by 3.2 nm and 54.2 nm in the short AIN MZI modulator 501 (Figure 7(g)) and in the long AIN MZI modulator 503 Figure 7 (h)), respectively. The dependence of the phase change on V is illustrated in Figure 7(i). Vs required for a p-phase shift (Vn) are 354 V and 27 V in the short and the long AIN MZI modulator 501, 503, respectively. Using the V-dependent temporal T spectrum in Figure 7(g) and Figure 7(h), the T - V curve is constructed and plotted in Figure 7(j). In the short AIN MZI modulator 501 at 1548 nm, T almost changes monotonically as V varies monotonically from - 200 V to 200 V. On the contrary, in the long AIN MZI modulator 503 at 1553.8 nm, T changes periodically under similar applied V. The higher voltage sensitivity of the long AIN MZI modulator 503 can be attributed to its longer Farm that provides a stronger E-field / light interaction. A sine fit is adopted for Figure 7(j) and a period of 716 V and 54 V is obtained in the short and the long AIN MZI modulator 501, 503, respectively, corresponding to their np values of 358 V and 27 V. The two np values are consistent with the np values extracted from Figure 7(i). Quantitatively, the ratio of the np values is 13.11 while the ratio of the two Farms is 12.99. The two close ratios reveal the proportionality between phase change and Farm under DC biases. The proportionality is further analyzed and confirmed by a theoretical analysis.
Specifically, the theoretical analysis is implemented to confirm the experimentally observed proportionality. Assuming the lengths of the two MZI arms are L and L+AL. At a zero bias, the phase accumulation of the two coherent light split by the Y-j unction at the entrance of the MZI can be expressed, respectively, by:
Figure imgf000021_0001
Equation S2
#¾ - t¾ x (I+ M% Equation S3 where l is the operating wavelength and n is the effective refractive index of the propagating mode in the MZE When a bias is applied, n will change by Dh to affect f i and 02. Since a push-pull architecture is adopted in the MZI design to enhance the modulation efficiency, the resultant ø 1 and 2 are:
Figure imgf000021_0003
quation S5
The consequent phase shift is:
Figure imgf000021_0002
Equation S6 The last term can be ignored since it involves the product of two small values, and Equation S6 is reduced to:
Figure imgf000022_0001
Equation S7
Therefore, at the same applied bias that results in the same Dh, the phase change is proportional to length L of the AIN MZI arm.
After the investigation of DC characteristics of the AIN MZI modulators, the alternating current (AC) characteristics are studied. Figure 8(a) and Figure 8(b) present the temporal spectrum of normalized T in the short and the long AIN MZI modulator respectively, under 10 kHz AC modulation signal with different magnitudes. The term ‘normalized tuning’ is defined as the opening of the temporal spectrum of the modulated T, i.e. the difference between the high and the low T value. In the short AIN MZI modulator, the normalized tuning gradually increases when the peak to peak voltage (Vpp) of the AC modulation signal rises from 20 V to 160 V in steps of 20 V, after which the normalized tuning almost saturates. A different behavior is observed in the long AIN MZI modulator, where the normalized tuning boosts to the maximum at 12 Vpp, then drops as Vpp further increases. The quantitative relation between normalized tuning and Vpp is plotted in Figure 8(c). The data points are extracted from Figure 8(a) and Figure 8(b). Absolute sine functions are employed for fitting since the normalized tuning cannot be negative. Fitted periods of 324 V and 27 V in the short and the long AIN MZI modulator 501, 503, respectively are revealed with R-squares higher than 0.99 for both conditions. The agreement in fitted periods in the case of DC and AC tuning suggests the speed of MZIs 501, 503 is faster than 10 kHz. The temporal T response of the short and the long MZI 501, 503 under 100-kHz AC modulation are plotted in Figure 8(d) and Figure 8(e) respectively. The optical waveforms can reproduce the voltage waveforms, demonstrating the effective transduction from electrical signal to photonic signal using the AIN MZI modulators at a 100- kHz data transmission rate. To further understand the AIN MZI modulators’ speed limit, a 3- dB measurement was implemented using a vector network analyzer (VNA). The measured results shown in Figure 8(f) indicate a 3-dB bandwidth of 0.9 MHz in the long AIN MZI modulator 503 and 1.1 MHz in the short AIN MZI modulator. The curve for the short AIN MZI has been moved up by 5 dB manually for visual clarity. Remarkably, the around 1-MHz modulation speed achieved in both AIN MZI modulators allows nanophotonic readout circuits to capture TESs’ signals with a temporal resolution of around 1 ps, which can satisfy most of the applications related to human/machine interactions, according to example embodiments. An interesting difference between the temporal T spectrum of the short and the long AIN MZI modulators under high AC voltages (Vpp > 13.5 V) is their distinct behaviors at waveform edges. As shown in Figure 8(d), the temporal T spectrum preserves the features of the input temporal V spectrum even at Vpp = 200 V in the short AIN MZI modulator. Contrarily, as suggested by Figure 7(j), when a square wave voltage is applied to the long AIN MZI modulator, T would experience several oscillations temporally depending on the magnitude of V at the square wave edges. Since the relation between T and V follows a sine function with a period of 54 V, the long AIN MZI modulator was operated at 1553.8 nm which corresponds to a zero-phase-wavelength in its wavelength spectrum (Figure 7(f)). Consequently, after every p-phase shift, T is expected to cross one peak or trough and return to the same value (Figure 7(j)). Such behaviors are observed and presented in Figure 8(g). A voltage pulse that sharply rises from 0 V to [27 x N] V is applied to the long MZI, where N is an integer ranging from 1 to 7. It is observed that N peak and troughs appear in the temporal T spectrum when [27 x N] V is applied, and T finally reaches the same level as T at 0 V.
Operation Principle of the Wearable Triboelectric-AIN NENS according to example embodiments
Figure 9(a)shows the impact force magnitude dependence of Vpp applied on the AIN MRR and the corresponding resonant wavelength shift. Figure 9(b) shows the load cell speed dependence of Vpp applied on the AIN MRR and the corresponding resonant wavelength shift. Figure 9(c) shows a contour map showing the dependence of resonant wavelength shift on impact force magnitude and contact area. Figure 9(d) shows the T-TES output voltage waveform generated by periodic motion of the force gauge and the characteristic T-TES stages in terms of contact/separation mode. Figures 9(e-i) show the resonance wavelength shift induced by T- TES voltage output and the corresponding optical transmission waveform at the operation wavelength of (e) 1555.455 nm, (f) 1555.48 nm, (g) 1555.525 nm, (h) 1555.531 nm, (i) 1555.555 nm. The best self-sustainable photonic modulation is achieved in (h), according to an example embodiment.
More specifically, in the integrated wearable NENS according to an example embodiment, the two electrodes from the T-TES are connected to the top and bottom electrodes that sandwich the AIN MRR (compare e.g. Figure 1), forming the electrical-photonic tuning system. The output characteristics of the T-TES when it is integrated with the AIN modulator in a NENS according to an example embodiment are firstly studied. As shown in Figure 9(a), the Vpp increases rapidly with impact force magnitude in the low impact force magnitude range and saturates at 235 V gradually in the high impact force magnitude range. This relationship has the same trend as the open-circuit voltage from the standalone T-TES in Figure 3(c), with the only difference in the absolute voltage magnitude. The reduction of voltage magnitude is mainly caused by the Baby Neill Constant (BNC) cables that are used to connect the AIN modulator and the T-TES for characterization. In practical applications according to example embodiment, the T-TES will preferably be directly connected to the AIN modulator without BNC cables and introduces almost no voltage reduction due to the minuscule capacitance of the AIN modulator. Based on the output characteristic, the corresponding A R can be obtained by the 0.39 pm/V sensitivity because the electrical signal from the T-TES is far slower than the intrinsic response time of the AIN modulator. Around 100 pm AAR can be achieved in the integrated system. Next, the dependence of Vpp and corresponding AAR on the load cell speed (at 200 N impact force magnitude) is also investigated and presented in Figure 9(b). The Vpp and AAR are both substantially unaffected by the load cell speed and only determined by the impact force magnitude. This independence of Vpp on the load cell speed further confirms that the T-TES is working in the open-circuit condition due to the capacitive nature of the AIN modulator. Testing of the T-TES as a human-machine interface is implemented. With finger tapping as the triggering, the resultant AAR shows notable increment with impact force magnitudes and contact areas. As for the AIN modulator, its optical characteristics are completely maintained since the electrical connection does not affect the optical path.
The detailed self-sustainable photonic modulation mechanism and phenomenon including the open-circuit voltage from the T-TES and the transmission spectrum from the AIN modulator 102 in an integrated NENS according to an example embodiment is presented in Figure 9(d) to Figure 9(i). The open-circuit voltage from the T-TES 900 has a periodic alternating waveform that is similar to a square-wave (Figure 9(d)). It is generated by the periodic motion of the force gauge. The deviation from the square-wave is caused by the dissipation of electrons to the humid environment. The detailed T-TES ’s 900 output characteristics (Figure 9(d)) and the corresponding AA R (Figure 9(e)) in the AIN modulator are examined in one cycle. At Stage 1, the load cell is in full contact with the T-TES with the pre-set impact force magnitude (contact mode of the T-TES 900), and the respective open-circuit voltage is zero. Then from Stage 1 to Stage 2, the load cell is moving up to the zero position and the two triboelectric layers are gradually separated from each other (separation mode of the T-TES 900) due to the device restoring force. Electric potential is rapidly built up with the separation, inducing a significant increment in the open-circuit voltage. The negative output is determined by the direction of electrode connection. The large negative voltage blueshifts AR of the AIN modulator. At Stage 2, the load cell is back to the zero position (separation mode of the T-TES 900) and the open- circuit voltage reaches the negative maximum. AR at this stage is at the leftmost position (Figure 9(e)). Next, from Stage 2 to Stage 3, the slow decrement of open-circuit voltage is due to charge dissipation of the system when the load cell is held still at zero position. Correspondingly, AR slowly redshifts. Then from Stage 3 to Stage 4, the load cell is moving down to contact with the T-TES 900 again (contact mode of the T-TES 900), thus the open-circuit voltage decreases towards zero rapidly during this period. Accordingly, a rapid redshift of AR of the AIN modulator is observed. It is worth to note that the open-circuit voltage at Stage 4 is above zero with maximum impact force magnitude, due to the drifting of the open-circuit voltage. Finally, the open-circuit voltage of T-TES 900 is drifted back to zero (Stage 1) and the next cycle begins.
The optical transmission waveform is strongly dependent on the operation wavelength. Thus, the optimal operation wavelength should be identified for the system according to various example embodiments for the best self-sustainable photonic modulation performance. In Figure 9(e) when the system according to an example embodiment is working at 1555.455 nm while AR is constant at 1555.525 nm with zero bias, the optical transmission waveform almost reproduces the T-TES 900 output voltage waveform. When the operation wavelength is 1555.48 nm which is closer to AR, a different waveform featuring a sharp trough from Stage 1 to Stage 2 is presented in Figure 9(f). As shown in the corresponding resonance shift, from Stage 1 to Stage 4, AR consecutively blue shifts strongly, redshifts slightly, and redshifts strongly. In each subfigure, the observed transmission from the previous stage is also marked in transparent circle. At Stage 1, the optical transmission is high since the operation wavelength is to the left of AR. From Stage 1 to Stage 2, due to the large blue shift, AR approaches, coincides with, and further shifts to the left side of the working wavelength, resulting in a sharp trough in the transmission. From Stage 2 to Stage 3, AR slowly redshifts, approaches, coincides with, and further shifts to the right side of the working wavelength, inducing a slow transaction of decrement and increment in transmission. Then from Stage 3 to Stage 4, a significant increment in transmission can be observed due to the rapid redshift of AR. Similarly, from Stage 4 to Stage 1, the open-circuit voltage gradually decreases back to zero when load cell maintains full contact with the T-TES 900. Due to the small decrement of voltage, AR only slightly blueshifts maintaining the high transmission level. At other working wavelengths, the operation principle is the same. Figure 9(g) shows that when the operation wavelength is exactly at AR, the optical transmission waveform features a sharp trough from Stage 3 to Stage 4. The best self- sustainable photonic modulation according to an example embodiment can be achieved when the operation wavelength is at 1555.531 nm, slightly longer than AR, as illustrated in Figure 9(h). A square optical transmission waveform is obtained without the presence of any sharp trough. Thus, “1” and “0” can be readily defined to realize binary operation. When the operation wavelength further moves to much longer wavelength at 1555.555 nm, the photonic modulation depth becomes shallow while the optical transmission waveform being the reverse of the initial T-TES 900 output voltage waveform.
As for continuous force sensing, conventionally it is only applicable when the TENG operates in the open-circuit mode but not the closed-circuit mode. Because in the closed-circuit mode, the charging/discharging process through the external circuit will screen the generated surface charges, during which the two output pulses in an operation cycle cannot fully reflect the continuous force information. Therefore, bulky and complicated external electrical circuits are required to activate TENG’s open-circuit operation mode. Thanks to the capacitive nature of the AIN modulator, a superior advantage of the integrated wearable NENS according to an example embodiment is the capability of enabling T-TES 900 to work under the open-circuit mode in a compact and easy-to-implement manner. While the T-TES 900 serves for continuous force sensing in the integrated system according to an example embodiment, the photonic module helps with transmitting the open-circuit sensing signal out in-situ through the optical signal, which can be detected by a photodetector circuit. In experiment, the wearable NENS according to example embodiments is working similarly to Figure 9(e) where the optical transmission spectrum replicates the waveform of the T-TES 900 modulating signal.
Figures 10(a-c) shows the impact force magnitude, the resultant applied voltage on the AIN modulator, together with the optical transmission spectrum at different load cell speeds of, (a) 900 mm/min, (b) 700 mm/min, and (c) 500 mm/min in a NENS according to an example embodiment. Figures 10(d-f) show zoom-in of the spectra in Figures 10(a-c) to a complete operation cycle, (d) 900 mm/min, (e) 700 mm/min, and (f) 500 mm/min. Figure 10 (g) shows a calibration curve showing the one-to-one correspondence of the optical transmission and the impact force magnitude at different load cell speeds. Figure 10(h) shows the proposed physical model that describes the integrated system according to an example embodiment. The T-TES is described by a parallel plate capacitor where the two plates are connected by a spring. The AIN MRR is described by a resonator with a Lorentzian resonant lineshape. More specifically, The detailed waveforms of the impact force, the resulting induced voltage on the AIN modulator, and the optical transmission spectrum are shown in Figure 10(a) to Figure 10(c), with different load cell speeds of 900, 700 and 500 mm/min. Figure 10(d) to Figure 10(f) present the zoom-in waveforms in a complete cycle, corresponding to the three load cell speeds respectively. As indicated by the four dash lines in the graphs in Figure 10(d) to (f), a cycle can be divided into three stages from left to right with respect to the force status applied on the T-TES. At Stage I, the load cell is approaching and gradually compresses the T- TES with the pre-set impact force magnitude. Due to the reduced gap between the top and the bottom friction layers, the induced voltage on AIN modulator decreases gradually with the impact force magnitude. As a result, the optical transmission from the AIN modulator 102 increases, following the same trend as the induced voltage visually. At Stage II, the load cell is in tight contact with the T-TES with the pre-set impact force magnitude; and the induced voltage is maintained at low level. The induced voltage is not zero at this stage is due to the open-circuit voltage shift arisen from the measurement instrument, while the small decrement of the induced voltage towards zero can be attributed to the slow charge dissipation of the system. A similar trend can also be found from the optical transmission of the AIN modulator. Then at Stage (III), the load cell is removed from and gradually releases the T-TES. Initially, the impact force magnitude decreases significantly from the full contact state to the critical contact state where the two friction surfaces are still in contact with each other, but the impact force magnitude is at a very low level. Thus, during this period, the induced voltage from the T-TES on the AIN modulator remains high. When the load cell is further removed, the two friction surfaces start to separate from each other; and the induced voltage on the AIN modulator gradually increases accordingly. Similarly, the same trend can also be found in the optical transmission waveform. Through analyzing the measurement results from different load cell speeds, the absolute value of the induced voltage as well as the optical transmission in the AIN modulator can reach and maintain a monotonous value that corresponds solely to the absolute magnitude of the impact force but is substantially not affected by the load cell speeds. At faster load cell speed, both the induced voltage and the optical transmission exhibit a higher increment or decrement rate, but the maximum values still maintain the same. It means that the optical transmission of the AIN modulator can follow the exact trend of the applied force on the T-TES, providing an advanced and easy-to-implement approach for continuous force sensing compared to the conventional open-circuit electrical voltage measurement.
A direct relationship of the resultant optical transmission and the impact force magnitude can be observed in Figure 10(g) in the NENS according to an example embodiment, which is extracted from Stage I in Figure 10(d) to Figure 10(f). This relationship serves as the calibration curve for continuous force sensing. As a fundamental requirement, a calibration curve should have a one-to-one relationship. The monotonically increasing optical transmission with the increasing impact force magnitude for the NENS according to an example embodiment fulfills the calibration curve requirement. Theoretical analysis is implemented to provide an analytical formula that can depict the full relationship between the impact force magnitude and the optical transmission, instead of only the measured discrete points. A physical model is proposed to describe the integrated system (Figure 10(h)). The T-TES is described by a parallel plate capacitor where the two plates with constant charge +Q and -Q are connected by a spring dominated by the stress-strain relation. The AIN MRR is described by a resonator with a Lorentzian resonant lineshape where the resonant wavelength is determined by the E-field across the parallel plate capacitor. The force on spring (F) determines the parallel plate capacitor’s voltage (V) and subsequently causes AAR through the Pockels effect. The resultant optical transmission (T) at the specific/operating wavelength is tuned continuously and follows the Lorentzian lineshape. After such formulation and with aid of the pre-determined Lorentzian resonant lineshape shown in Figure 4(b), the relation between the optical transmission and the impact force magnitude can be expressed as:
Figure imgf000027_0001
where T is the optical transmission and F is the impact force magnitude. D, K, N, B are fitting parameters where D is the separation between two plates without applying force, K and N are two coefficients in the stress-strain relationship, B is a mathematical fitting parameter without physical meaning. The data in Figure 10(g) is fitted well by the derived expression. More significantly, the fitted calibration curve is independent of the speed of the impact force. This benefits the continuous force sensing in practical applications using NENS according to example embodiments.
Theoretically, the integration of TESs and nanophotonic readout circuits can also be conveniently achieved through connecting the two TES electrodes to the pair of electrodes sandwiching the AIN MZI waveguide according to example embodiments. Due to the electrically capacitive nature of the AIN MZI modulator with a very small capacitance, the TESs work in the open-circuit condition without current flows that render electrical state shifts. The TES output voltage (VTES) is applied on the AIN MZI modulators, inducing an E-field across the AIN waveguide to change AlN’s refractive index through the electro-optic Pockels effect. In this way, T of AIN MZI carries the information delivered by VTES since T is governed by the refractive index. To confirm the feasibility of such example embodiments, the S-TES is integrated with the short AIN MZI modulator in one embodiment and the characteristics of the integrated system are explored. Figure 11(a) shows S-TES’s output voltage (VS-TES) under different Fs at 100 mm/min. The dependence of VS-TES on F follows a similar trend as Figure 3(a) that shows S-TES’s V0c without any integrated nanophotonic readout circuit. VS-TES abruptly increases from 16 V at 10 N to 80 V at 30 N, then gradually rises to 90 V at 60 N, and saturates afterward due to the full activation of surface charges in the triboelectrification process. The resultant T changes correspondingly to VS-TES. The VF dependence of VS-TES and the corresponding resultant T are presented in Figure 11(b). The independence of VS-TES on VF is preserved. The resultant T is also stable, showing the independence of VF. Figure 11(a) and Figure 11(b) together suggest that the S-TES’s characteristics are maintained after its integration with the short AIN MZI modulator, according to an example embodiment. Meanwhile, it is confirmed that the S-TES is working in the open-circuit condition, otherwise VS-TES would show VF-dependence. The detailed working principle of continuous real-time triboelectric force sensor enabled by nanophotonic readout according to an example embodiment is illustrated in Figure 11(c) to Figure 11(f). When VS-TES is at the lowest, the short AIN MZI modulator is initially working at l = 1546.7 nm which corresponds to a destructive interference with the lowest T. One force cycle is divided into four regions as illustrated by the differently shaded areas (Figure 11(c)). Region I refers to the zero-force stage where the two triboelectric layers are fully separated. The corresponding electrostatically induced VS-TES (- 25 V as shown in Figure 11(d)) maintains the lowest T (10 mV as shown in Figure 11(f)) in the nanophotonic readout circuit. In region II, F is gradually exerted on the S-TES so that the top triboelectric layer is approaching the bottom one. VS-TES increases and leads to the rise of T. Region III corresponds to the period when F exceeds the saturation value (60 N as shown in Figure 11(a)) while the two triboelectric layers are in tight contact. The resultant VS-TES keeps unchanged (90 V), so is T (28 mV). In region IV, the two triboelectric layers begin to separate apart from each other when F starts to drop. As F decreases to < 60 N, VS-TES and T begin to fall back to the lowest value. In one interaction cycle, the stimulus in the form of F mainly interacts with the integrated S-TES/nanophotonic sensing system in region II. Thus, region II is further explored in detail. Three critical force states are labeled by (T), (2) , and (3) respectively. At State (T), the load cell touches the top surface of the S-TES and F starts to increase. Between State (T) and (2), the two triboelectric layers are pressed towards each other without contact. F increases gradually due to the small elastic coefficient provided by the sponge spacer, causing a slight increase of VS-TES but a negligible change in T. At State (2), the two triboelectric layers are in contact, so F starts boosting due to the abrupt change of elastic coefficient. The corresponding VS-TES and T shoot up accordingly. While F boosts to the maximum around 190 N, VS-TES has already saturated at 90 V at State (3) of 60 N, with 27-mV T. Afterwards, F is maintained before it drops to 0 N. The temporal VS-TES and T spectrum follow the same trend. As indicated in Figure 11(c) to Figure 11(f), T is sensitive between State (2) and State (3). Therefore, the zoom-in figure showing the detailed temporal F-VS-TES-T spectrum in 11 - 14 s is presented in Figure 11(g). The temporal spectra in Figure 11(g) reveal the relation between F, VS-TES, and T. The relations between F, V, and T are theoretically governed by the following set of equations: in relation (B 1 ) e of parallel capacitor (B2)
Figure imgf000028_0001
optical transmission of MZI B(3) where K is the strength coefficient, n is the strain-hardening coefficient, s is the surface charge density of the triboelectric layer, k is the relative permittivity which is unity in our case where the dielectric material is air, e is the permittivity, To is the optical transmission at zero-phase, T’ is the amplitude of the oscillating AIN MZI wavelength spectrum, Vo is related to the initial phase, and np is the voltage required for a p-phase shift in the short AIN MZI modulator. Since the integrated TES/nanophotonics sensing system according to an example embodiment serves to read force information (F) from photonic readout (T), the one-to-one corresponding data extracted from Figure 11(g) to derive the resultant relation between T and F in the S-TES as:
Figure imgf000029_0001
According to Equation (Bl) to Equation (B4), one can derive the relation between voltage (V) and force (F) as:
Figure imgf000029_0002
Equation S8
And the relation between transmission (T) and F as:
Figure imgf000029_0003
Equation S9
The integrated spacer triboelectric sensor (S-TES)/nanophotonics sensing system according to an example embodiment is analyzed first. Figure 12 shows the measured relation between V and F with a one to one correspondence. The data is extracted from Figure 11(g). A boundary condition obtained from Figure 11(g) is:
F=-30 V, when F= 0 N, (Boundary condition 1) Using Boundary condition 1, Equation S8 leads to:
Figure imgf000029_0004
Equation s 10
Fitting the data in Figure 12 using Equation S10, the result is shown in the solid line with an R-square of 0.99.
Similarly, the measured relation between T and F is shown in Figure 13. A boundary condition is:
T= 9 mV, when F= 0 N, (Boundary condition 2)
Moreover, from the fitting result shown in Figure 6(j), one already obtained Vo = 341 V and Up = 360 V. Together with boundary condition 2 and Equation S10, Equation S9 leads to:
Figure imgf000029_0005
Equation S 11 Fitting the data in Figure 13 using Equation S 11, the resultant equation is presented in Equation (B4) above. The fitted curve is shown in the solid line with an R-square of 0.981 in Figure 13.
In the integrated textile triboelectric sensor (T-TES)/nanophotonics sensing system according to an example embodiment, the derivation process is the same. The V-F relation and T-F relation, as well as the fitted curves, are presented in Figure 14 and Figure 15 respectively. The resultant equation governing the T-F relation is presented in Equation (B5).
In the force range of 35 - 60 N, T and F are quasi-linearly related (Figure 11(h)). Hence, linear fitting is implemented and a sensitivity of 0.659 mV/N is obtained.
The design flexibility of TESs was further leveraged to extend the applicable force monitoring range of the integrated TES/nanophotonics sensing system according to an example embodiment. As shown in Figure 6 (j), the T-TES has a broader force monitoring range whose saturation point happens at 115 N instead of only 60 N in the S-TES. However, the voltage output of the T-TES (VT-TES) is lower than VS-TES. Consequently, the long AIN MZI modulator with higher voltage sensitivity is adopted to be integrated with the T-TES to compensate for the lower VT-TES. Like the short AIN MZI modulator, the long one is working at a destructive interference at 1551.7 nm when VT-TES is the lowest. Figure 16(a) presents VT-TES and the corresponding T characteristics of the integrated T-TES/nanophotonics sensing system according to an example embodiment under different Fs. VT-TES gradually increases from 40 V at 10 N to 65 V at 115 N with T falling from 32 mV at 10 N to 20 mV at 40 N, and then increasing to 28 mV at 115 N. Figurel6 (b) shows the VF-dependence of VT-TES and T. Using linear fitting, straight fitted lines with slopes of - 0.008 and 0.008 are derived for VT-TES and T respectively, suggesting that the T-TES is working in the open-circuit condition. Figure 16(c) to Figure 16(f) explain the working principle of the integrated T-TES/nanophotonics sensing system according to an example embodiment. As shown in Figure 16(c), one force cycle can be split into four regions with the same definitions as Figure 11(c). Region I and Region III are similar to Figure 11. Yet, Region II and Region IV where the temporal F spectrum shows sharp edges show different features. Interestingly, the temporal T spectrum in these two regions presents oscillations that produce a peak and a trough. To understand the interaction between the stimulus in the form of F and the T-TES in Stage II, 5 characteristic force states were identified, namely (T), (2), (3), (4) and (5). Before State (T), the load cell is not in contact with the top triboelectric surface so that no force is exerted on the T-TES. But VT-TES and the corresponding T drift slightly due to the dissipation of triboelectrically generated charges to the humid environment. In State (T) to State (2), the top triboelectric layer is pressed toward the bottom one. F mildly increases from 0 N to 7 N and VT-TES rises from -38 V to -29 V accordingly. Despite the small increment in F and VT-TES, T is lifted significantly from 22 mV to 33 mV thanks to the long AIN MZI modulator’s high voltage sensitivity. At State (2), the two triboelectric layers are in contact and F starts to rise abruptly. In force State (2) to State (3) , F and VT-TES keep increasing until VT-TES has increased by 27 V at State (3). At this moment, the long MZI experiences a p-phase shift so the interference changes from destructive to instructive. In State (3) to (4), F and VT-TES increase further until the voltage difference is 54 V at State (4). The long MZI undergoes a 2 -phasc shift and the interference returns to be destructive, resulting in the lowest T. Later at State (5), F exceeds 115 N where saturation happens with VT-TES of 65 V, leading to a stable T at around 30 mV afterward. Region IV can be explained similarly to Region II. Next, we zoom into Region II in 6.0 - 8.5 s for detailed quantitative analysis. The consolidated temporal spectra in Figure 16(g) reveal the relation between F, VT-TES, and T.
Extracted from Figure 16 (h) followed by a theoretical analysis, the resultant relation between T and F in T-TES can be described by Equation (B5):
7 = 3333
Figure imgf000031_0001
Equation (B5)
As described in detail above, the data are fitted well by the theoretical model suggested from Equation (Bl) to Equation (B3), with an R-squares of 0.939. In the force ranges of 7 - 70 N and 75 - 110 N, T and F are quasi-linearly related (Figure 16(h)). Hence, linear fitting is implemented too fit the data and a sensitivity of 0.174 mV/N and - 0.763 mV/N in the 7 - 70 N and 75 - 110 N force ranges, respectively, is obtained. Although F and T do not have a one- to-one correspondence in the integrated T-TES/nanophotonics sensing system according to an example embodiment, all F can be distinguished by further analyzing their slopes. A positive slope suggests the force range of 7 - 70 N while a negative slope indicates 75 - 110 N.
Diversified Applications of the Wearable Triboelectric-AIN NENS according to example embodiments
Figures 17(a-d) show a NENS 1700 according to an example embodiment in an optical Morse code transmission application - (a) Characterization setup, (b) Interface of the optical Morse code reader software, (c) the 26 distinguished alphabets transmitted by the optical Morse code, (d) Optical transmission of the information ‘HINUS’ using the wearable NENS. Figures 17(e&f) show a NENS 1700 according to an example embodiments in a continuous human motion monitoring application. The optical transmission spectrum (top) and the corresponding translated impact force magnitude (bottom) resulted from - (e) Arm patting, and (f) Walking. The calibration relies on the calibration curve in Figure 10(g).
More specifically, one of the major applications of wearable photonics is data transmission. Based on the self-sustainable photonic modulation and tuning function, the wearable NENS 1700 according to an example embodiment can be leveraged for optical Morse code transmission. Figure 17(a) shows the schematic of the corresponding measurement system. The optical signal is converted to the voltage signal by the photodetector and subsequently directed to a microcontroller unit (MCU) that serves as the interconnect between the integrated system and the computer. The Keithley electrometer together with the oscilloscope help to monitor the real-time voltage output from the T-TES of the NENS 1700. Once the processed signal is received by the computer, the custom-built software can translate the detected signal into the pre-defined alphabets whose array could convey the desired messages, as illustrated in Figure 17(b). Figure 17(c) demonstrates the transmission of all the 26 alphabets. And a message array conveying ‘HINUS’ is shown in Figure 17(d). In principle, all alphabets combinations are feasible to transmit arbitrary meaningful messages.
Another key application of wearable photonics is sensing. With the help of an integrated AIN modulator in the wearable NENS according to an example embodiment, continuous force sensing can be achieved to take advantage of merits from both sides. Here, the continuous human motion monitoring is demonstrated using a wearable NENS 1702, 1704 according to an example embodiment. Two monitoring scenarios of continuous force when the textile wearable NENS 1702, 1704 is attached on a human arm and sole, respectively, are investigated. For the NENS 1702 attached on the arm, cyclic finger tapping is applied on the device during the first 5 s. Then the fingers remain in contact with the device and press the device periodically for around 2 s. The same motion pattern is repeated starting from the cyclic finger tapping (Figure 17(e) top panel). For the NENS 1704 attached on sole, three walking patterns are subsequently applied on the device, i.e., normal walking, fast walking, and slow walking (Figure 17(f) top panel). The corresponding force spectra (Figure 17(e) and Figure 17(f) bottom panel) are derived by the pre-determined calibration curve (Figure 5(g)). The derived force spectrum from optical transmission replicates the actual impact force magnitude spectrum in a real-time manner, showing great potential of the integrated system according to example embodiments in practical applications for continuous force/pressure monitoring.
Design flexibility and more versatile applications according to example embodiments
Leveraging the design flexibility of TENG and nanophotonic readout circuits for force monitoring according to example embodiments, various linear sensitivities independent of force speed can be achieved in different force ranges. Toward practical applications, a smart glove according to an example embodiment based on the NENS was developed to realize continuous real-time robotic hand control and virtual/augmented reality (VR/AR) interaction.
Figures 18(a-c) show an elastic S-TES 1800 integrated with short AIN MZI modulator 1802 according to an example embodiment - (a) Schematic illustration of the S-TES 1800, (b) Schematic of the short AIN MZI modulator 1802 with an arm length (Larm) of 2.16 mm and footprint of 0.81 mm2, (c) Linear relation between Transmission and Force in the 35 - 60 N force range with a sensitivity of 0.659 mV/N. Figures 18(d-f) show a T-TES 1810 integrated with long AIN MZI modulator 1812 according to an example embodiment - (d) Schematic illustration of the elastic T-TES 1810, (e) Schematic of the long AIN MZI modulator 1812 (Larm = 28.06 mm, footprint = 1.38 mm2), (f) Linear relation between Transmission and Force in the 7 - 70 N force range with a sensitivity of 0.174 mV/N, and 75 - 110 N force range with a sensitivity of - 0.793 mV/N.
More specifically, as shown in Figure 18(a) to Figure 18(c), an elastic S-TES 1800 is integrated with a short AIN Mach-Zehnder Interferometer (MZI) modulator 1802 to realize linear force sensitivity of 0.659 mV/N in the range of 35 - 60 N. As shown in Figure 18(d) to Figure 18(f), a T-TES 1810 is integrated with a long AIN MZI modulator 1812 to achieve linear force sensitivity of 0.174 mV/N in 7 - 70 N and - 0.763 mV/N in 75 - 110 N. The design flexibility is advantageously provided by the broad material availability of S-TES 1800, T-TES 1810 and the critical impedance difference between AIN photonics 1802, 1812 and S-TES 1800, T-TES 1810.
Towards practical applications, a smart glove according to an example embodiment is fabricated based on the NENS as a human-machine-interface (HMI) for continuous real-time robotic control and virtual reality / augmented reality (VR/AR) interactions. Recently, smart gloves as HMIs have two major advances. One is integrating numerous sensors on a single glove for accurate tactile sensing [82]. Enabled by the large number of sensors, tactile sensing with great details can be achieved. Using deep learning methodology, the sensing information can reconstruct the hand motion exactly. The other direction is using a single glove for multivariant sensing, including temperature, strain, humidity, light, etc. In this way, the smart glove can mimic the complete human sensory system [83]. In comparison to existing smart gloves, the smart glove according to an example embodiment features self-sustainability and continuous real-time monitoring.
Figure 19(a) shows the schematic circuit diagram of the robotic hand 1902 control system according to an example embodiment. Figure 19(b) shows the optical signal output of the thumb and the corresponding signals of the other fingers from the glove 1900 according to an example embodiment for controlling the finger number and the movement speed of the robotic hand 1902. Inserts show photographs of the glove 1900 on the human hand and the robotic hand 1902, respectively.
More specifically, Figure 19(a) illustrates the circuit diagram adopted in an HMI robotic control application, as well as the physical quantities transduction that allows the information flow, according to an example embodiment. The information in the mechanical form is firstly converted into the electrical form via T-TES sensors e.g. 1904, 1905, then transforms into the photonic form by applying the electrical signal to AIN MZI modulator 1906. Finally, the photonic readout is used for robotic hand 1902 control. Five individual sensors e.g. 1904, 1905 are knitted on five fingertips of the glove 1900. Among them, in an example embodiment only the thumb sensor 1905 is connected to the long AIN MZI modulator 1906 to achieve the open- circuit condition; and the generated photonic signal is converted to voltage by a photodetector which is then connected to a microcontroller unit (MCU) for the analog-to-digital conversion. However, more than one of the sensors may be connected to a corresponding modulator in different example embodiments.
In an example embodiment, the other four T_TESs e.g. 1904 on the other fingers are directly connected to the MCU. However, the number of sensors directly connected to the MCU may be different in different example embodiments. It should be noted that the MCU here acts as the medium between the NENS 1910 according to an example embodiment and the robotic hand 1902, enabling real-time information transfer from T-TES sensors e.g. 1904, 1905 to the robotic hand 1902.
Robotic hand 1902 control is demonstrated using different movement speeds and numbers of human fingers. As shown in Fig. 19(b), when a balloon is pinched with the smart glove 1900, pulse-like signals are generated at the moment of contact and separation for the index, middle, ring and little finger, while the thumb signal shows continuous real-time changing curves related with force F and the duration of force, VF. Regarding conventional approaches of controlling robotic hands by TENG sensors, only two states, namely grasp or release, can be achieved in one operation cycle due to the transient pulse-like signal without any intermediate state. However, in this demonstration, as shown in Figure 19(b.ii), the robotic hand 1902 perfectly follows the movement of the human hand with the gradual grasping and releasing process as detected by the T-TES on the thumb operating in open-circuit condition. The insert images show in detail three states during the process, including the zero-F (box 1912), the medium-F (box 1914), and the maximum-F (box 1916) states. On top of the continuous real time control, the number of fingers can be manipulated. As shown in Figure 19(b.i, iii, iv, and v), when pinching and loosening the balloon using various numbers of fingers, the signals in each finger channel exhibit that the robotic hand 1902 responds with the same fingers and duration of force as the human hand.
In AR applications that combine the real and the virtual world, enhancing natural environments and offering perceptually enriched experiences, real-time interactions are highly required with the least information loss from the real world. Thus, taking advantage of the excellent sensitivity, high temporal resolution, and self-sustainability of a NENS according to an example embodiment, a flower planting process in AR space is demonstrated utilizing a triboelectric smart glove 1900 based NENS according to an example embodiment. The corresponding circuit diagram is similar to Figure 19(a).
Figure 20(a) shows screenshots of the flower planting process in the AR space. Inserts show detailed views of the corresponding gestures in each step. Figure 20(b) shows the output signals of the fingers in the flower planting process. Figure 20(c) shows a screenshot of continuous showering the flower in the AR space. The Insert shows pressing the T-TES for nanophotonic readout. Figure 20(d) shows the curve of optical output in continuous showering step. Inserts show the 3 showering angles of the watering can be controlled by different forces Fs.
More specifically, as demonstrated in Figure 20(a), with the smart glove 1900 worn, discrete actions in the AR flower planting process are defined by different gestures. Firstly, a flower is picked up when the index finger is contacted with the thumb, (i). Then, the separation between the index finger and the thumb commands planting the flower in the flowerpot, (ii). Subsequently, by contacting the middle finger with the thumb, scissors are picked up, (iii). And with one more contact of the middle finger with the thumb, the flower is pruned, (iv). It should be mentioned that the flower can be pruned for multiple times as long as the middle finger is contacted with the thumb. Afterward, once the ring finger is contacted with the thumb, the scissors are put down, (v). Lastly, a watering can and sunshine appear when contacting the little finger with the thumb, (vi). Figure 20(b) shows the corresponding electrical output signals of the four fingers (other than the thumb) in each step. Subsequently, the continuous real-time control capability is leveraged in the showering step by using the NENS according to an example embodiment (Fig. 20(c)). The showering angle of the can be adjusted in response to the states of an elastic S-TES sensor2000 placed on the table upon pressing. Figure 20(d) shows the continuous real-time changing curve of the photonic signal during the pressing process; and three specific showering angles under three pressing states with different forces Fs are displayed in the inserts.
As described above, a wearable triboelectric / aluminum nitride Nano-Energy-Nano-System (NENS) with self-sustainable photonic modulation and continuous force sensing functions is provided according to example embodiments. While existing studies focus on wearable optical illumination and optical detection, embodiments of the present invention aim at optical modulation and address the power consumption issue in modulator systems by integrating voltage -based AIN modulator and T-TES/S-TES power source. The synergy between AIN modulator and T-TES/S-TES brings two major advantages to the integrated system according to example embodiments. On the one hand, despite AlN’s moderate Pockels effect, the enhanced modulation is achieved in AIN modulators enabled by T-TES’s/S-TES's high voltage output. On the other hand, T-TES’s/S-TES's open-circuit operation mode can be facilitated by AIN modulator’s capacitive nature and consequently provides a compact and easy-to- implement system for continuous sensing. The characterization of individual AIN modulator and e.g. T-TES for use in example embodiments shows superior device performance respectively in terms of high-quality resonance lineshape (Q factor > 30,000, ER > 21 dB), stable DC tuning efficiency (0.4 pm/V), high AC modulation speed (> 3 GHz), and high voltage output (VpP > 300 V). Negligible performance degradation is observed after the system integration according to example embodiments because the AIN modulator can inherit the high-voltage from T-TES thanks to their capacitive nature. Optical Morse code transmission and continuous human motion monitoring are demonstrated according to example embodiments based on the two unique advantages respectively. Taking advantage of the design flexibility of TENG sensors and nanophotonic readout circuits, various linear force sensitivities are achieved in different force ranges. Integrating e.g. an elastic T-TES sensor with a short 2.16-mm-long AIN MZI modulator according to an example embodiment, a linear force sensitivity of 0.659 mV/N is achieved in the range of 35 - 65 N. Using e.g. a T-TES integrated with a longer 28.06-mm AIN MZI modulator according to an example embodiment with a higher voltage sensitivity, the force sensing range is extended to cover 7 - 110 N with a complementary linear sensitivity of 0.174 mV/N in 7 - 70 N and - 0.763 mV/N in 75 - 110 N. Notably, the linear force sensitivities are independent of force speeds, providing an important good property for practical applications. Towards practical applications, a smart glove based NENS according to an example embodiments is provided and continuous real-time control of robotics and VR/AR interactions are demonstrated, highlighting the stable, continuous real time, and information-lossless features.
It is noteworthy that the demonstrated integrated system according to example embodiments is not limited to the specified TENG sensors described for example embodiments, but applicable generally to all sensors that rely on the triboelectrification and electrostatic induction mechanisms. Similarly, the integrated system according to example embodiments is not limited to AIN for the optical modulators described for example embodiments, but applicable generally to optical materials with Pockels effect, so that these materials can be tuned by the high voltage from the TENGs. The NENS according to an example embodiment provides a versatile solution for self-sustainable wearable sensors for HMI applications.
This hybrid integration according to example embodiments is a crucial demonstration toward future self-sustainable wearable photonic ICs and tunable photonic sensors, which will find significant applications, including:
(1) Wearable electronics/photonics for IoT
(2) Wearable electronics/photonics for HMI
(3) Wearable electronics/photonics for smart home
(4) Wearable electronics/photonics for personalized healthcare monitoring
(5) Wearable electronics/photonics for robotics
(6) Wearable electronics/photonics for VR/AR interactions.
Embodiments of the present invention can provide one or more of the following features and associated benefits/advantages:
Integration of TENG and AIN photonics - Leverage the synergy between the high voltage output from TENG and the capacitive nature of AIN photonics.
Continuous self-sustainable TENG sensors leveraging photonics readout - Address the issue of the problematic pulse-like signals in TENG sensors. Enable continuous real-time self- sustainable TENG sensors.
Self-sustainable AIN photonics modulation using TENG - Low down the high power consumption caused by system-level photonic functions such as computation and (de)multiplexing .
Fabrication of aluminum nitride (AIN) Mach-Zehnder interferometer (MZI) modulators and AIN micro ring resonators (MRR) according to example embodiments
The AIN MZI modulator and AIN MRR share the same fabrication process. The fabrication started from a commercially available 8-inches Si wafer insulated by a thin layer of Si02. The bottom electrode was formed by a 120-nm TiN layer and a 50-nm S13N4 layer. Then the bottom electrode was covered by a planarized 2-pm S1O2 layer for insulation. The 2-pm S1O2 layer also served as the bottom cladding for light confinement in AIN waveguide. Next, a layer of 400-nm AIN was deposited after which a 200-nm S1O2 layer was deposited and patterned as the hard mask for AIN etching. After the formation of AIN waveguide patterns, another 2-pm planarized S1O2 layer was deposited as the upper cladding. Contact holes were opened followed by a 2-pm A1 layer deposition and patterning for bottom electrode contacts and top electrode formation Fabrication of spacer triboelectric sensor (S-TES) according to example embodiments
For S-TES, PTFE was utilized as the negative triboelectric material while aluminum foil served as the positive triboelectric material and electrode material. PET was utilized as the substrate of S-TES. A thin foam and a sponge were utilized as the spacer and the stage respectively. It should be noted that the foam here acted as the stage to ensure the contact of two triboelectric layers because simply pressing the sponge was unable to make sure of the contact. The surface areas of substrates are 5 x 5 cm2 and those of the inner stages, electrode materials, and triboelectric materials are 3 x 3 cm2. The thickness of the fabricated S-TES is 1 cm in total. Firstly, two thin foams were attached individually to two PET substrates in the middle, followed by attaching an aluminum foil to the other side of each foam. Subsequently, we attached a PTFE film to one of the aluminum foil surfaces. Lastly, two substrates were assembled in parallel. In between, four sponge strips were arranged on the four edges as the spacer, where the PTFE layer and the aluminum foil layer were positioned face to face. An S- TES could be obtained then.
Fabrication of textile triboelectric sensor (T-TES) according to example embodiments
For the T-TES, eco-flex and nitrile films were used as the triboelectric materials, carbon cloth as the electrode material, foam as the spacer, and textile as the sealing material for the whole device. The surface area of this fabricated sensor is 1.5 x 1.5 cm2 and the whole thickness is about 3 mm. Firstly, eco-flex solution was prepared by mixing component A and B in an 1:1 weight ratio. Then, it was uniformly blade-coated on one piece of carbon cloth. After solidifying, a negative triboelectric layer was obtained. Meanwhile, a nitrile film was attached to one side of another piece of carbon cloth as the positive triboelectric layer. Subsequently, the eco-flex and the nitrile layer were assembled face to face and in parallel with four foam strips in between as the spacer, which were arranged over the four edges of the two layers. Then, two textile pieces were attached individually to the other side of both carbon cloths for insulation and sealing. Lastly, with threads sewing the four edges of the device to enhance the attachment between layers, a T-TES could be obtained.
Characterization of triboelectric sensors according to example embodiments
A force gauge system (Mecmesin Multitest 2.5-i Test system) was utilized to apply forces with different magnitudes and speeds on the triboelectric sensors, and enable contact and separation process of the two triboelectric layers. A programable electrometer (Keithley 6514) was utilized to test the open-circuit voltage, and an oscilloscope (Agilent DSO-X3034A) was connected to it for real-time data acquisition.
Characterization of AIN MZI modulators according to example embodiments
A tunable laser source (Keysight, 81960A Tunable Laser) was utilized to emit the light, covering 1520 nm to 1610 nm with the minimum tuning step of 0.1 pm. The light was guided through a single-mode-maintaining polarization controller, then focused to the inversed tapered waveguide by a tapered fiber (OZ Optics, TSMJ- 3A-1550-9/125-0.25-18-2.5-14-3-AR), and finally guided to AIN MZI modulators. The voltage was applied to the AIN MZI modulators through a GSG probe with a 100- pm pitch (MPI, T26A GSG100). In the DC tuning characterization, a tunable DC voltage supply (Agilent, E3631A) was amplified by 20 times using a voltage amplifier (FLC Electronics, A400DI) before connected to the GSG probe. A power meter (Keysight, 81636B Power Sensor), synchronized with the tunable laser source was utilized for measuring the optical wavelength spectrum from the AIN MZI modulators. For the AC modulation, a waveform generator (HP, 33120A) was used as the power supply whose voltage was also amplified by 20 times before connected to the GSG probe. The modulated optical signals are amplified by an erbium-doped fiber amplifier (Thorlabs, EDFA100S) before captured by a high-speed photodetector (Thorlabs, DET08CFC/M.) and converted into RF output which was then captured by an oscilloscope (Agilent Technologies, DS093004L).
Characterization of integrated triboelectric sensors/nanophotonics sensing systems according to example embodiments
The general characterization is similar to that of the AIN MZI modulators and triboelectric sensors. The differences are as follows: Firstly, the voltage applied on the AIN MZI modulators is provided by connecting the GSG probe with triboelectric sensors. Secondly, for the demonstration part, the contact and separation process was controlled by the human hand instead of the force gauge.
Figure 21 shows a schematic drawings illustrating an integrated system 2100 according to an example embodiment, comprising a triboelectric device 2102 configured for generating a voltage output responsive to a force being applied to the triboelectric device 2102; and a capacitive structure 2104 connected to the triboelectric device 2102 for applying the voltage output from the triboelectric device 2102 across the capacitive structure 2104; wherein the capacitive structure 2104 comprises an optical modulator 2106 disposed between opposing electrodes 2108, 2110; and wherein the optical modulator 2106 is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device 2102 and hence the force applied to the triboelectric device 2102.
The optical modulator 2106 may comprise a microring resonator.
The optical modulator 2106 may comprise a Mach-Zehnder interferometer.
The triboelectric device 2102 may be textile based.
The triboelectric device 2102 may comprise material layers disposed on opposite sides of a flexible spacer structure.
The integrated system may comprise a plurality of triboelectric devices including the triboelectric device 2102 configured for generating the voltage output responsive to the force being applied thereto. One or more of the plurality of triboelectric devices may be configured for generating output voltage spikes responsive to a force being applied thereto.
The one or more triboelectric devices configured for generating output voltage spikes responsive to the force being applied thereto may be connected directly to a micro controller unit.
The micro controller may be configured to receive the modulated optical signal via a photodetector.
The integrated system may comprise a plurality of capacitive structures, each of the plurality of capacitive structures comprising a corresponding optical modulator disposed between opposing electrodes, and each of the plurality of capacitive structures being connected to a corresponding one of the plurality of triboelectric devices for applying the voltage output from the corresponding triboelectric device across said each capacitive structure, wherein each of the optical modulators may be configured to generate a modulated optical signal responsive to the output voltage from the corresponding triboelectric device and hence the force applied to the corresponding triboelectric device.
The integrated system may comprise a glove as carrier of the plurality of triboelectric devices.
Figure 22 shows a flowchart 2200 illustrating a method of generating modulation signals or sensor signals according to an example embodiment. At step 2202, a voltage output is generated responsive to a force being applied to a triboelectric device. At step 2204, the voltage output from the triboelectric device is applied across the capacitive structure connected to the triboelectric device, wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes. At step 2206, a modulated optical signal is generated responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device using an optical source coupled to the optical modulator.
The generated modulation signals or sensor signals may be used for one or more of a group consisting of wireless control/communication, healthcare monitoring, and human machine interface applications.
The method may comprise using one or more triboelectric devices to generate output voltage spikes responsive to a force being applied thereto.
The method may comprise using a plurality of capacitive structures, each of the plurality of capacitive structures comprising a corresponding optical modulator disposed between opposing electrodes, to generate a modulated optical signal responsive to the output voltage from a corresponding triboelectric device and hence the force applied to the corresponding triboelectric device.
Figure 23 shows a flowchart 2300 illustrating a method of fabricating an integrated system, according to an example embodiment. At step 2302, a triboelectric device is provided configured for generating a voltage output responsive to a force being applied to the triboelectric device. At step 2304, a capacitive structure is provided and connected to the triboelectric device for applying the voltage output from the triboelectric device across the capacitive structure; wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and wherein the optical modulator is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device.
The optical modulator may comprise a microring resonator.
The optical modulator may comprise a Mach-Zehnder interferometer.
The triboelectric device may be textile based.
The triboelectric device may comprise material layers disposed on opposite sides of a flexible spacer structure.
The method may comprise providing a plurality of triboelectric devices including the triboelectric device configured for generating the voltage output responsive to the force being applied thereto.
One or more of the plurality of triboelectric devices may be configured for generating output voltage spikes responsive to a force being applied thereto.
The method may comprise providing a micro controller unit directly connected to the one or more triboelectric devices configured for generating output voltage spikes responsive to the force being applied thereto.
The method may comprise providing a photodetector, wherein the micro controller is configured to receive the modulated optical signal via a photodetector.
The method may comprise providing a plurality of capacitive structures, each of the plurality of capacitive structures comprising a corresponding optical modulator disposed between opposing electrodes, and each of the plurality of capacitive structures being connected to a corresponding one of the plurality of triboelectric devices for applying the voltage output from the corresponding triboelectric device across said each capacitive structure, wherein each of the optical modulators is configured to generate a modulated optical signal responsive to the output voltage from the corresponding triboelectric device and hence the force applied to the corresponding triboelectric device.
The method may comprise providing a glove as carrier of the plurality of triboelectric devices.
Aspects of the systems and methods described herein may be implemented as functionality programmed into any of a variety of circuitry, including programmable logic devices (PLDs), such as field programmable gate arrays (FPGAs), programmable array logic (PAL) devices, electrically programmable logic and memory devices and standard cell-based devices, as well as application specific integrated circuits (ASICs). Some other possibilities for implementing aspects of the system include: microcontrollers with memory (such as electronically erasable programmable read only memory (EEPROM)), embedded microprocessors, firmware, software, etc. Furthermore, aspects of the system may be embodied in microprocessors having software -based circuit emulation, discrete logic (sequential and combinatorial), custom devices, fuzzy (neural) logic, quantum devices, and hybrids of any of the above device types. Of course the underlying device technologies may be provided in a variety of component types, e.g., metal-oxide semiconductor field-effect transistor (MOSFET) technologies like complementary metal-oxide semiconductor (CMOS), bipolar technologies like emitter- coupled logic (ECL), polymer technologies (e.g., silicon-conjugated polymer and metal- conjugated polymer-metal structures), mixed analog and digital, etc.
The above description of illustrated embodiments of the systems and methods is not intended to be exhaustive or to limit the systems and methods to the precise forms disclosed. While specific embodiments of, and examples for, the systems components and methods are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the systems, components and methods, as those skilled in the relevant art will recognize. The teachings of the systems and methods provided herein can be applied to other processing systems and methods, not only for the systems and methods described above.
It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive. Also, the invention includes any combination of features described for different embodiments, including in the summary section, even if the feature or combination of features is not explicitly specified in the claims or the detailed description of the present embodiments.
In general, in the following claims, the terms used should not be construed to limit the systems and methods to the specific embodiments disclosed in the specification and the claims, but should be construed to include all processing systems that operate under the claims. Accordingly, the systems and methods are not limited by the disclosure, but instead the scope of the systems and methods is to be determined entirely by the claims.
Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of "including, but not limited to." Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words "herein," "hereunder," "above," "below," and words of similar import refer to this application as a whole and not to any particular portions of this application. When the word "or" is used in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list and any combination of the items in the list. Reference
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Claims

1. An integrated system comprising: a triboelectric device configured for generating a voltage output responsive to a force being applied to the triboelectric device; and a capacitive structure connected to the triboelectric device for applying the voltage output from the triboelectric device across the capacitive structure; wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and wherein the optical modulator is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device.
2. The integrated system of claim 1, wherein the optical modulator comprises a microring resonator.
3. The integrated system of claim 1, wherein the optical modulator comprises a Mach- Zehnder interferometer.
4. The integrated system of any one of claims 1 to 3, wherein the triboelectric device is textile based.
5. The integrated system of any one of claims 1 to 4, wherein the triboelectric device comprises material layers disposed on opposite sides of a flexible spacer structure.
6. The integrated system of any one of claims 1 to 5, wherein the integrated system comprises a plurality of triboelectric devices including the triboelectric device configured for generating the voltage output responsive to the force being applied thereto.
7. The integrated system of claim 6, wherein one or more of the plurality of triboelectric devices are configured for generating output voltage spikes responsive to a force being applied thereto.
8. The integrated system of claim 7, wherein the one or more triboelectric devices configured for generating output voltage spikes responsive to the force being applied thereto are connected directly to a micro controller unit.
9. The integrated system of claim 8, wherein the micro controller is configured to receive the modulated optical signal via a photodetector.
10. The integrated system of any one of claims 6 to 9, comprising a plurality of capacitive structures, each of the plurality of capacitive structures comprising a corresponding optical modulator disposed between opposing electrodes, and each of the plurality of capacitive structures being connected to a corresponding one of the plurality of triboelectric devices for applying the voltage output from the corresponding triboelectric device across said each capacitive structure, wherein each of the optical modulators is configured to generate a modulated optical signal responsive to the output voltage from the corresponding triboelectric device and hence the force applied to the corresponding triboelectric device.
11. The integrated system of any one of claims 6 to 10, comprising a glove as carrier of the plurality of triboelectric devices.
12. A method of generating modulation signals or sensor signals comprising the steps of: generating a voltage output responsive to a force being applied to a triboelectric device; applying the voltage output from the triboelectric device across the capacitive structure connected to the triboelectric device, wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and generating a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device using an optical source coupled to the optical modulator.
13. The method of claim 12, wherein the generated modulation signals or sensor signals are used for one or more of a group consisting of wireless control/communication, healthcare monitoring, and human machine interface applications.
14. The method of claims 12 or 13, comprising using one or more triboelectric devices to generate output voltage spikes responsive to a force being applied thereto.
15. The method of any one of claims 12 to 14, comprising using a plurality of capacitive structures, each of the plurality of capacitive structures comprising a corresponding optical modulator disposed between opposing electrodes, to generate a modulated optical signal responsive to the output voltage from a corresponding triboelectric device and hence the force applied to the corresponding triboelectric device.
16. A method of fabricating an integrated system comprising the steps of: providing a triboelectric device configured for generating a voltage output responsive to a force being applied to the triboelectric device; and providing a capacitive structure connected to the triboelectric device for applying the voltage output from the triboelectric device across the capacitive structure; wherein the capacitive structure comprises an optical modulator disposed between opposing electrodes; and wherein the optical modulator is configured to generate a modulated optical signal responsive to the output voltage from the triboelectric device and hence the force applied to the triboelectric device.
17. The method of claim 16, wherein the optical modulator comprises a microring resonator.
18. The method of claim 16, wherein the optical modulator comprises a Mach-Zehnder interferometer.
19. The method of any one of claims 16 to 18, wherein the triboelectric device is textile based.
20. The method of any one of claims 16 to 19, wherein the triboelectric device comprises material layers disposed on opposite sides of a flexible spacer structure.
21. The method of any one of claims 16 to 20, comprising providing a plurality of triboelectric devices including the triboelectric device configured for generating the voltage output responsive to the force being applied thereto.
22. The method of claim 21, wherein one or more of the plurality of triboelectric devices are configured for generating output voltage spikes responsive to a force being applied thereto.
23. The method of claim 22, comprising providing a micro controller unit directly connected to the one or more triboelectric devices configured for generating output voltage spikes responsive to the force being applied thereto.
24. The method of claim 23, comprising providing a photodetector, wherein the micro controller is configured to receive the modulated optical signal via a photodetector.
25. The method of any one of claims 21 to 24, comprising providing a plurality of capacitive structures, each of the plurality of capacitive structures comprising a corresponding optical modulator disposed between opposing electrodes, and each of the plurality of capacitive structures being connected to a corresponding one of the plurality of triboelectric devices for applying the voltage output from the corresponding triboelectric device across said each capacitive structure, wherein each of the optical modulators is configured to generate a modulated optical signal responsive to the output voltage from the corresponding triboelectric device and hence the force applied to the corresponding triboelectric device.
26. The method of any one of claims 21 to 25, comprising providing a glove as carrier of the plurality of triboelectric devices.
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