CN106178259B - Rat leg muscle electrical stimulation and electromyographic signal acquisition flexible device and preparation method thereof - Google Patents
Rat leg muscle electrical stimulation and electromyographic signal acquisition flexible device and preparation method thereof Download PDFInfo
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Abstract
The invention provides a rat leg muscle electrical stimulation and electromyographic signal acquisition flexible device and a preparation method thereof, wherein the flexible device is provided with a plurality of independent finger electrodes, and a certain gap is reserved between each finger electrode; a plurality of stimulating electrodes are distributed on each finger-shaped electrode according to a certain interval, and a plurality of ground electrodes are distributed around each stimulating electrode and used for effectively controlling the current diffusion range and accurately controlling the micro-electrical stimulation area; a plurality of recording electrodes are distributed on the central symmetry line of the whole flexible device, and reference electrodes are distributed near the recording electrodes; the flexible device is integrated with a micro-electrical stimulation interface and an electromyographic signal acquisition interface at the same time, and can synchronously apply micro-electrical stimulation and record electromyographic signals at different positions. The functional electrical stimulation and electromyographic signal acquisition functions are integrated, and the optimized device structure and the flexibility of the polymer material ensure that the device has good shape retention property when being attached and effectively transmits the stimulation current and the electrophysiological signals.
Description
Technical Field
The invention relates to a microelectrode in the technical field of biomedical engineering, in particular to a flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition and a preparation method thereof.
Background
Paralysis is a decrease or loss of voluntary motor function and is a common symptom of the nervous system. Paralysis is caused by upper and lower motor neurons, pyramidal tracts and peripheral neuropathy, and paralysis of muscles in a large area can seriously affect the life quality of patients and cause heavy burden to families and society. At present, the main rehabilitation means comprise traditional methods such as instrument training, medicine assistance, traditional Chinese medicine acupuncture and moxibustion and the like, and have a certain recovery effect on slight transient muscle paralysis, and the basis of the paralysis rehabilitation is established on the integrity of the nerve system of a human body to a muscle innervation loop.
In recent years, some novel paralysis rehabilitation technologies, such as peripheral nerve repair methods based on implantable microsystems, mainly based on histology and cytology, aiming at slight nerve injury, the reconnection of nerves is strictly time-efficient, and the rehabilitation technology cannot be used for serious injury or paralysis; the paralysis rehabilitation system based on the artificial limb or the exoskeleton bypasses the paralyzed muscles, utilizes an artificial mechanical structure to replace the function of the paralyzed muscles, can realize simple mechanical limb actions, cannot realize fine actions, has great help for amputation or patients with muscular tissue lesion, but can cause muscular atrophy for paralyzed patients with normal muscular tissues by using the method for a long time; the paralysis rehabilitation implantable artificial nervous system based on electric stimulation is used for replacing the function of damaged nerves aiming at a paralysis patient with normal muscle tissue function, realizing electrophysiological monitoring and electric stimulation on muscles and nerve tissues, bypassing the damaged nerves to directly enable the muscles to act, and having potential to enable the patient to recover the self-care ability of life.
As the invasiveness of the nerve electrodes increases, so does the risk. Thanks to the rapid development of mems (micro electro mechanical systems) technology, implantable artificial nervous systems continue to decrease in size, continue to increase in integration density, decrease invasiveness, and have the potential to adapt to complex and delicate nerve and muscle tissues. The paralyzed rehabilitation implantable artificial nervous system is mainly divided into three paralyzed rehabilitation implantable artificial nervous systems of a central nerve, a peripheral nerve and skeletal muscles according to the classification of an electric stimulation target of an implantable artificial nerve electrode, wherein the electric stimulation is mainly applied to the skeletal muscles, and the paralyzed muscles are subjected to motion prediction and feedback stimulation by detecting myoelectric signals of normal muscles.
A search of the prior art found that Ethier C, Oby E R, Bauman M J et al in Nature, 2012, 485 (7398): 368-371 writing: "Restoration of grandis following analysis through controlled stimulation of muscles" they developed a complex implantable artificial nervous system, by implanting microelectrodes of monkey brain, recording signals from neurons of motor cortex to directly predict action intention of muscles needing paralysis rehabilitation, after blocking brachial plexus with local anesthetic, they formed triggering sequence of electrical stimulation by using predicted electromyographic signals to directly electrically stimulate muscles, realized more complex action, can simply grab ball. The use of wire electrodes is limited to the electrical stimulation of muscles, and the resolution and integration level are low, so that the contraction of the muscles on the arms cannot realize more complex actions.
Guo L, Guvanasen G S, Liu X et al in IEEE transactions on biomedicalcitimes and systems, 2013, 7 (1): 1-10 written article: the PDMS flexible material-based extensible microelectrode array is 60 micrometers in thickness and good in shape retention, and by applying square wave voltage of 40Hz, 100 microseconds and 0.8V to the left shin nerve of a cat, the myoelectric signal of the medial gastrocnemius of the right limb is measured in the reflection process of the contralateral extensor.
Kangxiayang, Liujing, Tianhongchang et al, in Sensors & actors B Chemical, 2016, 225:267-278, drafts: the invention discloses a flexible electrode with 16 electrode points based on a Parylene C polymer material, and through modifying iridium oxide on the electrode, the signal-to-noise ratio is reduced, and the stimulation current threshold is improved. But the stimulating electrode and the recording electrode are separately used, the relative positions of the electrodes are uncertain, and the coverage range is small.
In summary, most of the currently reported flexible devices for muscle electrical stimulation and electromyographic signal acquisition are stimulation and acquisition separation, and the electrical stimulation lacks good spatial resolution, and cannot realize precise and complex actions.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition, which is improved and innovated on the existing electrode structure and process, integrates a stimulation electrode and a recording electrode, increases the coverage range and the adhesion shape retention of the electrodes, and improves the spatial resolution of electrical stimulation.
According to one aspect of the invention, a flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition is provided, wherein the flexible device is provided with a plurality of independent finger electrodes, and a certain gap exists between each two finger electrodes; a plurality of stimulating electrodes are distributed on each finger-shaped electrode according to a certain interval, and a plurality of ground electrodes are distributed around each stimulating electrode and used for effectively controlling the current diffusion range and accurately limiting the micro-electrical stimulation area;
a plurality of recording electrodes are distributed on the central symmetry line of the whole flexible device, and reference electrodes are distributed near the recording electrodes;
the flexible device is integrated with a micro-electrical stimulation interface and an electromyographic signal acquisition interface at the same time, and can synchronously apply micro-electrical stimulation and record electromyographic signals at different positions.
Preferably, the flexible device is butterfly-shaped in appearance, the left side and the right side of the flexible device are symmetrical, the left side and the right side of the flexible device respectively comprise a plurality of independent finger-shaped electrodes which are divided into an upper part and a lower part; wherein:
the left side and the right side of the upper part respectively comprise a plurality of finger electrodes with equal width, and the length of the finger electrodes is gradually reduced from top to bottom and is used for coating the back part and the side part of the thigh of the hind limb of the rat;
the left side and the right side of the lower part respectively comprise a plurality of finger electrodes with the same width, and the length of the finger electrodes is gradually reduced from top to bottom and is used for coating the back part and the side part of the lower leg of the hind limb of the rat.
Preferably, gaps are reserved between adjacent finger electrodes, the length of each finger electrode is different, the size of the gaps between the adjacent finger electrodes and the length of the finger electrodes are determined according to the actual size of the leg of the rat, the coverage area of the finger electrodes is large, and meanwhile the relative position between the adjacent finger electrodes is convenient to control during attaching.
Preferably, the micro-electrical stimulation interface and the electromyographic signal acquisition interface have the same structure and comprise multiple paths, and are accessed to the electrophysiological recording and electrical stimulation system through a universal Zero Insertion Force (ZIF) socket; wherein:
in the multichannel microelectrostimulation interface: part of the micro-electrical stimulation interfaces are used for connecting the stimulation electrodes and are used for micro-electrical stimulation, and the rest micro-electrical stimulation interfaces are connected with all the ground electrodes surrounding the stimulation electrodes;
in the flesh electricity signal acquisition interface: and a part of the electromyographic signal acquisition interfaces are used for connecting the recording electrodes and acquiring electromyographic signals, and the rest of the electromyographic signal acquisition interfaces are connected to be used as reference electrodes.
More preferably, in the micro-electrical stimulation interface for micro-electrical stimulation:
a plurality of stimulating electrodes are distributed on each of the plurality of finger-shaped electrodes on the single side of the upper part, a plurality of stimulating electrodes at the farthest end of each finger-shaped electrode are connected into a path, and the like inwards;
a plurality of stimulating electrodes are distributed on each of the plurality of finger electrodes on the single side of the lower part, a plurality of stimulating electrodes at the farthest end of each finger electrode are connected into a path, and the like inwards.
Preferably, in the electromyographic signal acquisition interface for electromyographic signal acquisition, the recording electrodes have the same spacing, are uniformly distributed on the symmetrical center line of the flexible device from top to bottom, and are at the same height position as the stimulating electrodes in the same row on each finger electrode.
Preferably, the flexible device comprises three polymer insulation layers and two metal circuit layers arranged between the three polymer insulation layers at intervals, and the second metal circuit layer exposed out of the top polymer insulation layer comprises: the device comprises a micro-electrical stimulation interface, an electromyographic signal acquisition interface, a ground electrode, a stimulation electrode, a reference electrode and a recording electrode, wherein the stimulation electrode and the recording electrode are modified by iridium oxide.
According to another aspect of the present invention, there is provided a method for preparing a flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition, the method comprising the steps of:
step 1: cleaning and baking a silicon wafer by using the silicon wafer as a substrate;
step 2: thermally evaporating or sputtering a layer of metal on the silicon chip to be used as a final release layer of the upper layer structure;
and 3, step 3: making a bottom polymer insulating layer, wherein the polymer is polyimide or parylene;
and 4, step 4: sputtering a chromium/platinum metal layer, throwing photoresist on the chromium/platinum metal layer, carrying out photoetching patterning, and obtaining a first metal circuit layer by ion beam etching or wet etching;
and 5, step 5: repeating the step 3, manufacturing an interlayer polymer insulating layer, and patterning to expose: all electrode points are a stimulating electrode, a ground electrode, a recording electrode, a reference electrode point, a micro-electrical stimulation interface, an electromyographic signal acquisition interface and places where a first layer of metal circuit layer and a second layer of metal circuit layer need to be connected;
and 6, step 6: repeating the step 4 to obtain a second metal circuit layer;
and 7, step 7: repeating the step 3, manufacturing a top polymer insulating layer, and exposing all electrode points, the micro-electro-stimulation interface and the electromyographic signal acquisition interface in a graphical mode;
and 8, step 8: patterning the photoresist to expose all the stimulating electrodes and all the recording electrodes;
step 9: sputtering a titanium/iridium oxide layer, soaking in acetone and slightly performing ultrasonic treatment to remove the photoresist;
step 10: and corroding the metal release layer to finish the release of the flexible device.
Preferably, in the step 2, the metal material of the release layer is aluminum or chromium/copper, and the thickness of the release layer is 200-1000 nm.
In the 9 th step: the titanium metal is used as a seed layer, and the thickness of the seed layer is 20-50 nm;
the iridium oxide adopts a reactive sputtering mode, the thickness of the iridium oxide is 200-500 nm, and the iridium oxide comprises the following components in percentage by weight: the iridium oxide is modified on the stimulating electrode and used for improving the charge storage capacity, and the range of the stimulating current which can be loaded in each path is expanded to hundreds of microamperes; and the iridium oxide is modified on the recording electrode and is used for reducing electrochemical impedance, improving the signal-to-noise ratio and ensuring the good signal pickup capacity of the flexible device.
Compared with the prior art, the invention has the following beneficial effects:
the flexible device is used for carrying out micro-electrical stimulation on skeletal muscles of the legs (lower limbs) of a rat and collecting myoelectric signals, a plurality of relatively independent finger-shaped electrodes are designed according to the sizes of the legs of the actual adult rat, and meanwhile, a flexible polymer material is adopted to ensure good shape retention during attachment, so that the effective transmission of stimulation current and electrophysiological signals is promoted; a circle of ground electrodes surrounds the periphery of the stimulating electrodes, so that the current diffusion range can be effectively controlled, and the accurate control of a stimulating area is realized; the stimulation and collection interfaces are on the same device, and the interface form is universal, so that the multi-channel electrophysiological workstation can perform synchronous stimulation and collection conveniently; the stimulating electrode and the recording electrode are modified with iridium oxide, so that the electrochemical impedance is effectively reduced, and the signal-to-noise ratio and the charge storage capacity are improved; the flexible device provides a new tool for the research of the motor paralysis rehabilitation animal model.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1(a) is a schematic view of an overall structure of a flexible device according to an embodiment of the present invention;
FIG. 1(b) is an enlarged view of a portion of the structure shown in FIG. 1;
FIG. 2(a) is a partial enlarged view of a finger electrode according to an embodiment of the present invention;
FIG. 2(b) is an illustration of the arrangement of the stimulating electrodes and the ground electrodes according to one embodiment of the present invention;
FIGS. 3 (a) - (j) are flow charts of a manufacturing process according to an embodiment of the present invention;
FIG. 4 is an exploded view of a three-dimensional structure of a flexible device with a double-layer metal circuit layer sandwiched by three polymer insulating layers according to an embodiment of the present invention;
fig. 5 (a) - (c) are schematic diagrams and experimental photographs showing the attachment of the flexible device to the skeletal muscle of the lower limb of a rat according to an embodiment of the present invention;
in the figure: the system comprises a micro-electrical stimulation interface 1, an electromyographic signal acquisition interface 2, ground electrodes 3 (eight ground electrodes 3-1, 3-2, 3-3, 3-4, 3-5, 3-6, 3-7 and 3-8), a stimulation electrode 4, a reference electrode 5 and a recording electrode 6;
a bottom polymer insulation layer 11, a first metal circuit layer 12, a middle polymer insulation layer 13, a second metal circuit layer 14, and a top polymer insulation layer 15.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
As shown in fig. 1(a) and 1(b), a flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition is provided with a plurality of independent finger-shaped electrodes, and a certain gap is formed between each finger-shaped electrode; a plurality of stimulating electrodes 4 are distributed on each finger-shaped electrode according to a certain interval, and a plurality of ground electrodes 3 are distributed around each stimulating electrode and used for effectively controlling the current diffusion range and accurately controlling the micro-electrical stimulation area;
a plurality of recording electrodes 6 are distributed on the central symmetry line of the whole flexible device, and reference electrodes 5 are distributed near the recording electrodes 6;
the flexible device is integrated with a micro-electrical stimulation interface 1 and an electromyographic signal acquisition interface 2 at the same time, and can synchronously apply micro-electrical stimulation and record electromyographic signals at different positions.
As a preferred embodiment, the flexible device is butterfly-shaped in appearance, and has symmetrical left and right sides, and the left and right sides respectively comprise 16 independent finger-shaped electrodes which are divided into an upper part and a lower part; wherein:
the left side and the right side of the upper part respectively comprise 10 finger-shaped electrodes with equal width, and the length of the 10 finger-shaped electrodes is gradually reduced from top to bottom and is used for coating the back part and the side part of the thigh of the hind limb of the rat;
the left side and the right side of the lower part respectively comprise 6 finger-shaped electrodes with equal width, and the length of the 6 finger-shaped electrodes is gradually reduced from top to bottom and is used for coating the back part and the side part of the lower leg of the hind limb of the rat.
Further, gaps are reserved between adjacent finger electrodes, the length of each finger electrode is different, and the size of the gaps between the adjacent finger electrodes and the length of the finger electrodes are determined according to the actual size of the leg of the rat, wherein: the gap between adjacent finger electrodes is controlled to be 0.05-0.5 mm, so that the coverage area of the finger electrodes is large, and the relative position between the adjacent finger electrodes is convenient to control during attaching; as shown in fig. 1b, a spacing of 0.1mm between individual finger electrodes is illustrated.
Furthermore, the micro-electrical stimulation interface and the electromyographic signal acquisition interface have the same structure and comprise 20 circuits, and are connected with an electrophysiological recording and electrical stimulation system through a universal zero-insertion-force socket; wherein:
16 paths of the 20 micro-electrical stimulation interfaces are connected with the stimulation electrodes and used for micro-electrical stimulation, and the rest 4 paths of the interfaces are connected with all ground electrodes surrounding the stimulation electrodes;
16 paths of the 20 electromyographic signal acquisition interfaces are connected with a recording electrode and used for electromyographic acquisition, and the rest 4 paths of electromyographic signal acquisition interfaces are connected to be used as reference electrodes.
Further, 16 lines are used in the micro-electrical stimulation interface of micro-electrical stimulation:
5 stimulating electrode points are distributed on each of 10 finger electrodes on the single side of the upper part, the 10 stimulating electrode points at the farthest end of each finger electrode are connected to form 1 path, the rest is analogized inwards, and the total number of the 10 paths are on the two sides of the upper part;
each of the 6 finger electrodes on the single side of the lower part is distributed with 3 stimulating electrode points, the 6 stimulating electrode points at the farthest end of each finger electrode are connected to form 1 path, the rest is analogized inwards, and the total number of the 6 paths on the two sides of the lower part is 6.
In the electromyographic signal acquisition interface for acquiring the electromyographic signals of 16 paths, the 16 recording electrodes have the same distance and are uniformly distributed on the symmetrical middle line of the flexible device from top to bottom, and the recording electrodes and the stimulating electrode points on the same row on each finger-shaped electrode are at the same height position.
8 ground electrodes are distributed around each stimulating electrode to ensure that stimulating current is distributed in a rectangular area surrounded by the 8 ground electrodes, so that the current diffusion range and the action stimulating area are accurately controlled; and the electrode spacing can be adjusted to enlarge or reduce the area of the rectangular region, so that specific stimulation can be performed on muscles in different regions.
Of course, the number and length of the finger electrodes, and the number of other electrodes and interfaces, can be designed according to the specific rat hindlimb model and stimulation and recording requirements, and are not limited to the above description.
Based on the device structure, in a specific embodiment, the shape and the size of the micro-electrical stimulation interface 1 and the electromyographic signal acquisition interface 2 are the same, and are respectively connected with a zero-insertion-force socket, the zero-insertion-force socket is respectively connected with a ZIF-Clip interface of the electrophysiological workstation, and the ZIF-Clip interface keeps the position of the whole flexible device through an interface clamp ZCD-ROD32(Tucker-Davis Technologies, USA); the number of the stimulating electrodes 4 is 136, and 8 ground electrodes 3 are arranged around each stimulating electrode 4; 16 recording electrodes 6 are arranged on the symmetrical middle line of the flexible device and are positioned at the same height position with the stimulating electrodes 4 on the same row on each finger-shaped electrode; the reference electrode 5 corresponding to the recording electrode 6 is composed of three large rectangular electrodes, the diameter of the stimulating electrode 4, the recording electrode 6 and the ground electrode 3 is 200 microns, the distance between adjacent finger electrodes is 0.1mm, the distance between adjacent stimulating electrodes 4 is the smallest 1.5mm (the lowest end of the lower part is close to the middle), the largest 5.5mm (the uppermost end of the upper part is close to the outer side), and the distance between the recording electrodes 6 is 3 mm.
As shown in fig. 2(a) and 2(b), which are illustrations of arrangements of the stimulation electrodes and the ground electrodes according to an embodiment, 8 ground electrodes 3-1 to 3-8 surround a single stimulation electrode 4, and stimulation current is concentrated in an area surrounded by the ground electrodes 3-1 to 3-8, so that overlapping interference between adjacent stimulation electrodes 4 is avoided, and stimulation precision and spatial resolution are ensured.
As shown in (a) - (j) of fig. 3, the method for preparing the flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition is prepared according to the following steps:
1) as shown in fig. 3 (a), a layer of 1 micron thick aluminum is thermally evaporated as a release layer on a 500 micron thick silicon wafer;
2) as shown in fig. 3 (b), a layer of photosensitive polyimide Durimide7505 is spin-coated on the aluminum release layer, and a patterned bottom polyimide insulating layer is prepared by pre-baking, exposing, developing and curing, wherein the thickness of the bottom polyimide insulating layer is 3 μm;
3) as shown in fig. 3 (c), a layer of chromium and a layer of platinum are sputtered on the underlying polyimide insulating layer, the thicknesses of chromium and platinum being 30 nm and 200 nm, respectively;
4) as shown in (d) in fig. 3, spin-coating a 5-micron-thick positive photoresist AZ4620 on the basis of 3), performing pre-baking, photoetching, developing and post-baking, performing wet etching by using an etching solution, and controlling the etching time to obtain a patterned first metal circuit layer;
5) as shown in (e) of fig. 3, spin-coating a layer of photosensitive polyimide Durimide7505 on the basis of 4), and performing pre-baking, exposure, development and curing to obtain a patterned middle-layer polyimide insulating layer, wherein the thickness of the middle-layer polyimide insulating layer is 3 microns;
6) as shown in fig. 3 (f), a layer of chromium and a layer of platinum are sputtered on the basis of 5), the thicknesses of chromium and platinum being 30 nm and 200 nm, respectively;
7) as shown in (g) in fig. 3, spin-coating a 5 μm thick positive photoresist AZ4620 on the basis of 6), and performing pre-baking, photolithography, development and post-baking, wet etching by using an etching solution, and controlling the etching time to obtain a patterned second metal circuit layer;
8) as shown in fig. 3 (h), spin-coating a layer of photosensitive polyimide Durimide7505 on the basis of 7), and performing pre-baking, exposure, development and curing to obtain a patterned top polyimide insulating layer, wherein the thickness of the top polyimide insulating layer is 2 microns;
9) as shown in (i) in fig. 3, spin-coating a positive photoresist AZ4903 with a thickness of 30 microns on the basis of 8), and exposing all stimulating electrodes and recording electrodes through pre-baking, photoetching, developing and post-baking; sputtering a layer of titanium and a layer of iridium oxide, wherein the thickness of the titanium is 50 nanometers, the thickness of the iridium oxide is 300 nanometers, soaking in acetone and slightly performing ultrasonic treatment to remove photoresist, and modifying the stimulating electrode and the recording electrode with iridium oxide;
10) as shown in (j) of fig. 3, an electrochemical etching method is used on the basis of 9), in a NaCl solution (the concentration of the solution needs to be capable of electrolyzing enough chloride ions to react with hydrogen ions generated by electrolyzed water to generate enough diluted hydrochloric acid to etch an aluminum release layer), the whole silicon wafer with the device is placed on an anode of an electrolytic cell, the voltage is 0.7-1.0V, and the aluminum release layer is etched to the flexible device to automatically fall off.
In another embodiment, the preparation method of the flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition comprises the following steps:
1) sputtering a layer of chromium/copper metal with the thickness of 200 nanometers on a glass substrate to be used as a release layer;
2) depositing a Parylene C film with a thickness of 3 μm on the release layer by Chemical Vapor Deposition (CVD), i.e. the bottom polymer insulation layer 11 (as shown in fig. 4);
3) spin-coating a negative photoresist NR7-3000PY with the thickness of 3 microns, and performing pre-baking, photoetching, developing and post-baking to complete patterning;
4) sputtering a layer of titanium and a layer of gold, wherein the thicknesses of the titanium and the gold are respectively 30 nanometers and 300 nanometers, and obtaining a first graphical metal circuit layer 12 (shown in figure 4) by a lift off process;
5) depositing a layer of Parylene C film with the thickness of 3 microns;
6) spin-coating 20-micron-thick positive photoresist AZ4903, carrying out photoetching development, taking unexposed photoresist as a mask for Reactive Ion Etching (RIE), completing the patterning of the middle polymer insulating layer 13 (shown in figure 4), and etching the outline of the bottom polymer insulating layer;
7) spin-coating a negative photoresist NR7-3000PY with the thickness of 3 microns, and performing pre-baking, photoetching, developing and post-baking to complete patterning;
8) sputtering a layer of titanium and a layer of gold, wherein the thicknesses of the titanium and the gold are respectively 30 nanometers and 300 nanometers, and obtaining a patterned second metal circuit layer 14 (shown in figure 4) by a lift off process;
9) depositing a layer of Parylene C film with the thickness of 3 microns;
10) spin-coating 20-micron-thick positive photoresist AZ4903, carrying out photoetching development, taking unexposed photoresist as a mask for Reactive Ion Etching (RIE), and finishing the patterning of the top polymer insulating layer 15 (shown in FIG. 4);
11) spin-coating a positive photoresist AZ4903 with the thickness of 30 microns, exposing all stimulating electrodes and recording electrodes through pre-baking, photoetching, developing and post-baking, sputtering a layer of titanium and a layer of iridium oxide, wherein the thickness of the titanium is 50 nanometers, the thickness of the iridium oxide is 300 nanometers, soaking in acetone and slightly performing ultrasonic treatment to remove the photoresist, and modifying the stimulating electrodes and the recording electrodes with iridium oxide;
12) and removing the release layer by using a chromium/copper corrosive liquid to release the flexible device from the glass substrate.
As shown in fig. 4, the three-dimensional structure of the flexible device prepared by the above method is an exploded view of the three-layer polymer insulating layer sandwiching the two-layer metal circuit layer; in some embodiments, the polymer used is a photosensitive polyimide, and the three polymer insulating layers include: a bottom polyimide insulating layer 11, a middle polyimide insulating layer 13, and a top polyimide insulating layer 15; the bi-layer metal circuit layer includes: a first metal circuit layer 12 and a second metal circuit layer 14. A first metal circuit layer 12 and a second metal circuit layer 14 are disposed at intervals between the bottom polyimide insulating layer 11, the middle polyimide insulating layer 13, and the top polyimide insulating layer 15. The second metal circuit layer exposed from the top polymer insulation layer comprises: the device comprises a micro-electrical stimulation interface 1, an electromyographic signal acquisition interface 2, a ground electrode 3, a stimulation electrode 4, a reference electrode 5 and a recording electrode 6. The flexible device has larger size and denser wiring, and the micro-processing yield of the device cannot be ensured if the line width of a single-layer metal wire is smaller, so that the line width can be ensured to be 100 microns by adopting double-layer metal, and the reliability of the device is greatly improved.
As shown in fig. 5 (a) - (c), a schematic diagram and experimental photographs of the flexible device attached to the skeletal muscle of the lower limb of a rat are shown, the flexible device (shown in fig. 5 (a)) prepared by the above method is attached to the skeletal muscle of the leg of the rat (shown in fig. 5 (b)), the size of the flexible device is matched with the shape of the thigh, in the animal experiment (shown in fig. 5 (c)), the skin of the leg of the rat is carefully removed to completely expose the undamaged muscle tissue, the flexible device is lightly attached to ensure that an array of recording electrodes at the symmetrical center line of the flexible device is just behind the leg of the rat, the finger electrodes at the left and right sides of the flexible device are attached to the side of the muscle of the leg of the rat, the contact between the device and the muscle is wetted with physiological saline, and the flexible device is tightly attached to the muscle under the van der waals force, it is difficult to displace it without applying a large force. Different micro-electrical stimulation modes are combined on the muscle of the leg of the rat, and the device obtained by the embodiment is practical and good in effect through the collected different myoelectric signals and the observed different motion modes of the leg of the rat.
The flexible device is manufactured by adopting a flexible MEMS process, the materials are selected from platinum and polyimide with biocompatibility, the total thickness is only 8 micrometers, good shape retention during attaching is ensured, and the effective transmission of stimulating current and electrophysiological signals is promoted;
the flexible device is designed according to the actual size and shape of the hind limb of the rat, and is effectively attached to most of the side parts and the back muscles of the whole hind limb through a plurality of independent finger-shaped electrodes, and simultaneously, a circle of ground electrodes is surrounded around the stimulating electrodes to effectively control the current diffusion range, so that the current distribution in the region is uniform, the synchronous activation of muscle cells in the stimulated region is facilitated, and the accurate control of the stimulated region is realized;
the flexible device has the advantages that the electrical stimulation interface and the electromyographic signal acquisition interface are independently separated, so that the multichannel electrophysiological workstation can synchronously apply micro-electrical stimulation and acquire electrophysiological signals; the stimulation and collection interfaces are on the same device, and the interface form is universal, so that the multi-channel electrophysiological workstation can perform synchronous stimulation and collection conveniently;
the flexible device is composed of three polymer insulating layers and two metal circuit layers, and iridium oxide is modified on the stimulating electrode and the recording electrode, so that the electrochemical impedance is effectively reduced, the charge storage capacity is improved, and the signal-to-noise ratio and the charge storage capacity are improved.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (9)
1. A flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition is characterized in that the flexible device is provided with a plurality of independent finger electrodes, and a certain gap is reserved between each finger electrode; a plurality of stimulating electrodes are distributed on each finger-shaped electrode according to a certain interval, and a plurality of ground electrodes are distributed around each stimulating electrode and used for effectively controlling the current diffusion range and accurately limiting the micro-electrical stimulation area;
a plurality of recording electrodes are distributed on the central symmetry line of the whole flexible device, and reference electrodes are distributed near the recording electrodes;
the flexible device is integrated with a micro-electrical stimulation interface and an electromyographic signal acquisition interface at the same time, and can synchronously apply micro-electrical stimulation and record electromyographic signals at different positions;
the flexible device is butterfly-shaped in appearance, the left side and the right side of the flexible device are symmetrical, the left side and the right side of the flexible device respectively comprise a plurality of independent finger-shaped electrodes which are divided into an upper part and a lower part; wherein:
the left side and the right side of the upper part respectively comprise a plurality of finger electrodes with equal width, and the length of the finger electrodes is gradually reduced from top to bottom and is used for coating the back part and the side part of the thigh of the hind limb of the rat;
the left side and the right side of the lower part respectively comprise a plurality of finger electrodes with the same width, and the length of the finger electrodes is gradually reduced from top to bottom and is used for coating the back part and the side part of the lower leg of the hind limb of the rat.
2. A rat leg muscle electrical stimulation and electromyographic signal acquisition flexible device according to claim 1, wherein a gap is formed between every two adjacent finger electrodes, the length of each finger electrode is different, the size of the gap between every two adjacent finger electrodes and the length of each finger electrode are determined according to the actual size of a rat leg, the coverage area of the finger electrodes is large, and meanwhile, the relative position between every two adjacent finger electrodes is convenient to control during attaching.
3. The rat leg muscle electrical stimulation and electromyographic signal acquisition flexible device according to claim 1, wherein the micro electrical stimulation interface and the electromyographic signal acquisition interface have the same structure and comprise multiple paths, and are connected to an electrophysiological recording and electrical stimulation system through a universal zero insertion force socket; wherein:
in the multichannel microelectrostimulation interface: part of the micro-electrical stimulation interfaces are used for connecting the stimulation electrodes and are used for micro-electrical stimulation, and the rest micro-electrical stimulation interfaces are connected with all the ground electrodes surrounding the stimulation electrodes;
in the flesh electricity signal acquisition interface: and a part of the electromyographic signal acquisition interfaces are used for connecting the recording electrodes and acquiring electromyographic signals, and the rest of the electromyographic signal acquisition interfaces are connected to be used as reference electrodes.
4. A rat leg muscle electrical stimulation and electromyographic signal acquisition flexible device according to claim 3, wherein in the micro-electrical stimulation interface for micro-electrical stimulation:
a plurality of stimulating electrodes are distributed on each of the plurality of finger-shaped electrodes on the single side of the upper part, a plurality of stimulating electrodes at the farthest end of each finger-shaped electrode are connected into a path, and the like inwards;
a plurality of stimulating electrodes are distributed on each of the plurality of finger electrodes on the single side of the lower part, a plurality of stimulating electrodes at the farthest end of each finger electrode are connected into a path, and the like inwards.
5. A rat leg muscle electrical stimulation and electromyographic signal collection flexible device according to claim 3, wherein in the electromyographic signal collection interface for electromyographic signal collection, the recording electrodes are equally spaced from top to bottom and are evenly distributed on a symmetry center line of the flexible device, and are at the same height position as the stimulation electrodes on the same row on each finger electrode.
6. A rat leg muscle electrical stimulation and electromyographic signal collection flexible device according to any one of claims 1-5, wherein the flexible device comprises three polymer insulation layers and two metal circuit layers arranged between the three polymer insulation layers at intervals, and the second metal circuit layer exposed out of the top polymer insulation layer comprises: the device comprises a micro-electrical stimulation interface, an electromyographic signal acquisition interface, a ground electrode, a stimulation electrode, a reference electrode and a recording electrode, wherein the stimulation electrode and the recording electrode are modified by iridium oxide.
7. A method for preparing a flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition according to any of claims 1 to 6, comprising the steps of:
step 1: cleaning and baking a silicon wafer by using the silicon wafer as a substrate;
step 2: thermally evaporating or sputtering a layer of metal on the silicon chip to be used as a final release layer of the upper layer structure;
and 3, step 3: making a bottom polymer insulating layer, wherein the polymer is polyimide or parylene;
and 4, step 4: sputtering a chromium/platinum metal layer, throwing photoresist on the chromium/platinum metal layer, carrying out photoetching patterning, and obtaining a first metal circuit layer by ion beam etching or wet etching;
and 5, step 5: repeating the step 3, manufacturing an interlayer polymer insulating layer, and patterning to expose: all electrode points are a stimulating electrode, a ground electrode, a recording electrode, a reference electrode point, a micro-electrical stimulation interface, an electromyographic signal acquisition interface and places where a first layer of metal circuit layer and a second layer of metal circuit layer need to be connected;
and 6, step 6: repeating the step 4 to obtain a second metal circuit layer;
and 7, step 7: repeating the step 3, manufacturing a top polymer insulating layer, and exposing all electrode points, the micro-electro-stimulation interface and the electromyographic signal acquisition interface in a graphical mode;
and 8, step 8: patterning the photoresist to expose all the stimulating electrodes and all the recording electrodes;
step 9: sputtering a titanium/iridium oxide layer, soaking in acetone and slightly performing ultrasonic treatment to remove the photoresist;
step 10: and corroding the metal release layer to finish the release of the flexible device.
8. The preparation method of the flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition according to claim 7, wherein in the step 2, the metal material of the release layer is aluminum or chromium/copper, and the thickness of the release layer is 200-1000 nm.
9. The method for preparing the flexible device for rat leg muscle electrical stimulation and electromyographic signal acquisition according to claim 7, wherein in the 9 th step:
titanium is used as a seed layer, and the thickness of the seed layer is 20-50 nm;
the iridium oxide adopts a reactive sputtering mode, the thickness of the iridium oxide is 200-500 nm, and the iridium oxide comprises the following components in percentage by weight: the iridium oxide is modified on the stimulating electrode and used for improving the charge storage capacity, and the range of the stimulating current which can be loaded in each path is expanded to hundreds of microamperes; and the iridium oxide is modified on the recording electrode and is used for reducing electrochemical impedance, improving the signal-to-noise ratio and ensuring the good signal pickup capacity of the flexible device.
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| CN110638448A (en) * | 2019-10-01 | 2020-01-03 | 华东交通大学 | Full-flexible polymer interface for bidirectional human-computer interaction application |
| CN111870240B (en) * | 2020-08-28 | 2024-01-26 | 江西脑虎科技有限公司 | Flexible deep brain electrode integrating thermal stimulation and electrographic recording and preparation method thereof |
| CN112741640B (en) * | 2020-12-10 | 2022-11-04 | 中国科学院深圳先进技术研究院 | Real-time ultrasonic stimulation electric signal recording chip and preparation method thereof |
| CN113855034A (en) * | 2021-09-10 | 2021-12-31 | 北京大学 | Microneedle electrode and method for producing same |
| CN115363592B (en) * | 2022-08-31 | 2023-12-12 | 上海脑虎科技有限公司 | Implantable probe device, preparation method thereof, electrode device and electronic equipment |
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