Hydrogel for electrically controlled adhesive electrostimulation electrode and preparation method and application thereof

Abstract

The application belongs to the technical field of biological medicine, and discloses a hydrogel for electrically controlled adhesive electrostimulation electrodes and a preparation method and application thereof. Components of the hydrogel include a phosphate buffer, an ionic liquid, an enoic acid monomer, a boric acid monomer and a polyaspartic acid-o-dihydroxyphenyl monomer. The enoic acid monomer contains carboxylic acid, can form hydrogen bonds and electrostatic bonds with the skin, the o-dihydroxyphenyl group in the polyaspartic acid-o-dihydroxyphenyl monomer forms chemical bonds, and [EMIM] + in the ionic liquid can form electrostatic bonds with the skin, thereby ensuring the adhesion of the hydrogel. The hydrogel can change the size of the adhesion by electrolysis, so that the electrode has characteristics suitable for patients of different ages and different parts of the human body, and the damage to the skin is reduced. By introducing a flexible substrate layer, the combination of the hydrogel adhesion layer and the conductive layer is improved, so that the electrically controlled adhesive electrostimulation electrode has stronger stretchability, effectively realizes electrostimulation and collects high-quality electromyograms.

Description

Technical Field

[0001] This invention belongs to the field of biomedical related technology, and more specifically, relates to a hydrogel for an electrically controlled viscous electrostimulation electrode, its preparation method and application. Background Technology

[0002] In recent years, research achievements in materials and processes have driven the development and application of bioelectrodes. Bioelectrodes with high stretchability and flexibility can directly contact the skin in a conformal manner, adapting to skin deformation. Therefore, flexible epidermal electrodes have been widely used in electrophysiological signal acquisition and nerve stimulation in recent years. Nerve stimulation, in particular, plays a crucial role in neurological diagnosis and rehabilitation. The peripheral nervous system, as the center of limb perception and movement, is closely related to daily life. Damage to the peripheral nerves often leads to limited limb perception and movement, causing significant inconvenience to patients' normal lives.

[0003] Current commercially available medical devices for neurological diagnosis are expensive and mostly employ rigid electrical stimulation electrodes, typically made of metallic or silicon-based materials. Rigid electrodes have poor resistance to motion artifacts and a large Young's modulus, making conformal adhesion difficult. Furthermore, due to the varying locations of peripheral nerve damage in patients, commercially available electrodes often exhibit low signal fidelity when monitoring patients of different ages (infants, adults, and the elderly) and different skin sites (finger, elbow, leg, etc.). This is often due to their large modulus, uncontrollable viscosity, and rapid signal decay. Insufficient viscosity can cause unnecessary discomfort to patients. Therefore, optimizing electrode flexibility, viscosity, and improving their anti-artifact capabilities and signal fidelity are important directions for developing novel flexible electrodes.

[0004] Most current flexible electrodes achieve their stretchability by coating stretchable conductive materials onto a stretchable substrate. These electrodes often exhibit poor adhesion and low signal quality. Researchers have attempted to improve this by coating the skin / electrode interface with an adhesive flexible conductive adhesive; however, this adhesive is too sticky, easily causing unnecessary damage to delicate or hairy skin. Furthermore, the adhesive's stickiness is not repeatable and decays quickly, failing to meet the viscosity requirements of electrostimulation electrodes. Therefore, developing a highly stretchable flexible electrostimulation electrode with adjustable viscosity holds great promise in the medical field. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a hydrogel for an electrically controlled viscous electrostimulation electrode, its preparation method, and its applications. The provided hydrogel can have its viscosity altered through electrolysis, enabling the electrode to be suitable for patients of different ages and different body parts, while minimizing skin damage. By introducing a flexible base layer to improve the bonding between the hydrogel's viscous and conductive layers, the electrically controlled viscous electrostimulation electrode exhibits greater stretchability, allowing it to adhere tightly to the patient's skin while effectively providing electrical stimulation and acquiring high-quality electromyography (EMG).

[0006] To achieve the above objectives, according to one aspect of the present invention, a hydrogel for an electrically controlled viscous electrostimulation electrode is provided, the hydrogel comprising phosphate buffer, ionic liquid, olefinic monomer, boric monomer and polyaspartic acid-catechol monomer.

[0007] Acetic acid monomers contain carboxylic acids, which can form hydrogen bonds and electrostatic bonds with the skin; the catechol groups in polyaspartic acid-catechol monomers form chemical bonds, while [EMIM] in ionic liquids... + It can form electrostatic bonds with the skin, thus ensuring the adhesion of the hydrogel.

[0008] Furthermore, the hydrogel also includes an initiator and a crosslinking agent, wherein the mass fractions of the olefinic monomer, the boric monomer, the initiator, the crosslinking agent, and the polyaspartic acid-catechol monomer are 15wt%-25wt%, 0.5wt%-2wt%, 0.01wt%-0.05wt%, 0.02wt%-0.1wt%, and 2wt%-5wt%, respectively; and the mass ratio of the phosphate buffer and the ionic liquid is 1:1.

[0009] Further, the ionic liquid includes any one or more of [EMIM]Cl, [EMIM]Ac, [EMIM]Br, [BMIM]Cl, [BMIM]Ac, and [BMIM]Br; the olefinic monomers include any one or more of acrylic acid, butenoic acid, hexenoic acid, and their derivatives; the boric acid monomers mainly include any one or more of boric acid, sodium borate, phenylboronic acid, and their derivatives; the catechol monomer in the polyaspartic acid-catechol monomer is any one or more of dopamine, 2-amino-3-(4-hydroxyphenyl)propionic acid, and their derivatives; the initiator is any one of α-ketoglutarate, Irgacure2959, and Irgacure1173; and the crosslinking agent is any one of N,N'-methylenebisacrylamide and polyethylene glycol (diol) diacrylate.

[0010] Furthermore, the viscosity of the hydrogel is regulated by electrolysis.

[0011] Furthermore, the hydrogel achieves viscosity regulation under the electrolysis of an active metal anode and an inert cathode electric field. The active metal electrode is any one of Zn, Fe, Sn, and Pb; the inert electrode is any one of Pt, Au, and graphite.

[0012] The present invention also provides a method for preparing a hydrogel for an electrically controlled viscous electrostimulation electrode as described above. First, a PBS solution with pH=7.4 and an ionic liquid are uniformly mixed to obtain a hydrogel solvent. Then, an olefinic monomer, a boric monomer, an initiator, and a crosslinking agent are dissolved in the hydrogel solvent and magnetically stirred until completely dissolved. Then, a polyaspartic acid-catechol monomer is added and stirred evenly. After degassing, the hydrogel is obtained.

[0013] The present invention also provides the application of the hydrogel for the electrically controlled viscous electrostimulation electrode as described above in the electrically controlled viscous electrostimulation electrode. The electrically controlled viscous electrostimulation electrode includes a hydrogel viscous top layer, a flexible base layer, a stretchable conductive layer and a hydrogel viscous bottom layer arranged from top to bottom. The hydrogel viscous top layer and the hydrogel viscous bottom layer are both prepared using the hydrogel for the electrically controlled viscous electrostimulation electrode as described above.

[0014] Furthermore, the flexible substrate layer is made of styrene-butadiene block copolymer, which can be replaced by PDMS or Ecoflex; the stretchable conductive layer is made of stretchable silver-gallium indium alloy conductive material.

[0015] Furthermore, the electrode achieves changes in viscosity and enhancement of mechanical structure through electrolysis.

[0016] Furthermore, by connecting the two ends of the electrode to a Zn electrode and a Pt electrode respectively, and connecting the positive terminal of the power supply to the Zn electrode and the negative terminal of the power supply to the Pt electrode, after electrolysis begins, zinc ions are generated by anodic electrolysis, which form metal coordination bonds with carboxylate ions in the hydrogel, thereby increasing the tensile / fracture strength of the hydrogel and reducing its viscosity. Alternatively, by connecting the two ends of the electrode to a Zn electrode and a Pt electrode respectively, and connecting the positive terminal of the power supply to the Pt electrode and the negative terminal of the power supply to the Zn electrode, after electrolysis begins, hydroxide ions are generated by anodic electrolysis and hydrogen ions are generated by cathodic electrolysis, thereby increasing the viscosity.

[0017] In summary, compared with the prior art, the hydrogel for electrically controlled viscous electrostimulation electrodes, its preparation method, and its application provided by this invention have the following beneficial effects:

[0018] 1. The provided hydrogel can achieve viscosity regulation through electrolysis. Connect an active metal electrode (Zn electrode) and an inert electrode (Pt electrode) to the two ends of the hydrogel electrode, respectively. Connect the positive terminal of the power supply to the Zn electrode and the negative terminal of the power supply to the Pt electrode. After electrolysis begins, zinc ions are generated by anodic electrolysis and hydroxide ions are generated by cathodic electrolysis. The pH value of the solution increases, thereby causing the borate ester bond to combine with the catechol group. This reduces the number of catechol groups that bind to the skin surface, thus reducing the Schiff base reaction and Michael addition with the skin. At the same time, more carboxyl groups are converted into carboxylate ions, which combine with [EMIM]+, resulting in a weakening of the electrostatic coupling with the carboxyl groups on the skin surface. This synergistic effect leads to a decrease in viscosity.

[0019] 2. The provided hydrogel can restore its viscosity through electrolysis. Connect the two ends of the hydrogel electrode to Pt and Zn electrodes respectively. Connect the positive terminal of the power supply to the Pt electrode and the negative terminal to the Zn electrode. After electrolysis begins, hydroxyl ions are generated at the anode and hydrogen ions are generated at the cathode. The pH value of the hydrogel surface in contact with the skin decreases, which causes the borate ester bond to break with the catechol group. This results in an increase in the number of catechol groups bound to the skin surface, enhancing the Schiff base reaction and Michael addition with the skin. At the same time, more carboxyl groups are converted into carboxyl groups, and the electrostatic coupling between the [EMIM]+ ions released and the carboxyl groups on the skin surface is strengthened, thus synergistically leading to increased viscosity.

[0020] 3. The provided hydrogel can be enhanced in mechanical structure through electrolysis. Connect the two ends of the hydrogel electrode to Zn electrode and Pt electrode respectively, connect the positive terminal of the power supply to the Zn electrode and the negative terminal of the power supply to the Pt electrode. After the electrolysis starts, zinc ions are generated by anodic electrolysis, which form metal coordination bonds with carboxylate groups in the hydrogel, thereby enhancing the mechanical properties of the hydrogel, such as tensile strength and fracture strength.

[0021] 4. The electrically controlled viscous electrostimulation electrode has a four-layer structure. The top and bottom hydrogel viscous layers are hydrogel layers, and their viscosity is controlled by electrolysis to adapt to different skin conditions. The flexible base layer is composed of hydrogenated styrene-butadiene block copolymer, which has good stretchability and enhances the bonding between the hydrogel viscous layer and the conductive layer. The conductive layer is composed of silver, hydrogenated styrene-butadiene block copolymer, toluene, and a gallium-indium alloy, exhibiting high sensitivity and excellent conductivity. The entire electrically controlled viscous electrostimulation electrode, while fulfilling its intended function, has a simple structure and outstanding deformability, enabling a simple, effective, and low-cost fabrication process.

[0022] 5. The preparation of the electrically controlled viscous electrostimulation electrode mainly includes the preparation of hydrogel and silver-gallium indium alloy conductive material. It has low production cost, simple and easy-to-operate overall process, and is easy to mass-produce. The materials used in the preparation method, such as polyaspartic acid and hydrogenated styrene-butadiene block copolymer, are all non-toxic and harmless, ensuring the safety of production personnel and users and achieving environmental protection.

[0023] 6. The mass content of key components in hydrogels and silver-gallium indium alloy conductive materials was reasonably set, which enabled the hydrogels and silver-gallium indium alloy conductive materials to have better technical effects. The material performance will be reduced if the mass content is below or above this range. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating a method for preparing a hydrogel for an electrically controlled viscous electrostimulation electrode provided by the present invention, where a1 represents each step.

[0025] Figure 2 This is a schematic diagram of the structure of the electrically controlled viscous electrostimulation electrode provided by the present invention;

[0026] Figure 3 (a) and (b) in the figure are the initial state diagram and the stretched state diagram of the conductive layer, respectively.

[0027] Figure 4 (a) and (b) in the text are respectively Figure 1 Schematic diagram of the electrolytic viscosity change principle of hydrogel in [the process].

[0028] Figure 5 The adhesion strength change diagram of the hydrogel before and after electrolysis provided by the present invention;

[0029] Figure 6 In the diagram, 'a' is a diagnostic diagram of sensory nerves, and 'b' is a diagnostic diagram of motor nerves.

[0030] Figure 7 (a), (b), and (c) in the image are comparison diagrams of sensory nerve electromyography (EMG) signals in normal individuals and patients, proximal motor nerve EMG signals, and distal motor nerve EMG signals, respectively.

[0031] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-flexible substrate layer, 4-stretchable conductive layer, 401-gallium indium alloy, 402-micron-sized silver sheet, 6-hydrogel layer, 7-human skin, 8-nerve, 18-normal human sensory nerve signal, 19-normal human proximal motor nerve signal, 20-normal human distal motor nerve signal, 21-patient sensory nerve signal, 22-patient proximal motor nerve signal, 23-patient distal motor nerve signal. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0033] This invention provides a hydrogel for an electrically controlled viscous electrostimulation electrode. The hydrogel comprises phosphate-buffered saline (PBS), an ionic liquid, an olefinic monomer, a boric acid monomer, a polyaspartic acid-catechol monomer, an initiator, and a crosslinking agent. The mass fractions of the olefinic monomer, the boric acid monomer, the initiator, the crosslinking agent, and the polyaspartic acid-catechol monomer are 15wt%-25wt%, 0.5wt%-2wt%, 0.01wt%-0.05wt%, 0.02wt%-0.1wt%, and 2wt%-5wt%, respectively; the mass ratio of PBS to the ionic liquid is 1:1.

[0034] Acetic acid monomers contain abundant carboxylic acids, which can form hydrogen bonds and electrostatic bonds with the skin. The catechol groups in polyaspartic acid-catechol monomers form abundant chemical bonds, while [EMIM] in ionic liquids... + It can form electrostatic bonds with the skin, thus ensuring the excellent adhesion of the hydrogel.

[0035] Under the electrolysis of an active metal anode and an inert cathode, the hydrogel undergoes oxidation at the anode and reduction at the cathode, generating a large amount of hydroxyl radicals. This increases the pH value and weakens the chemical interaction of the catechol groups with the electrostatic attraction of the ionic liquid, thus reducing viscosity. Simultaneously, metal cations diffuse into the hydrogel, forming metal coordination bonds with the abundant carboxyl groups in the polyaspartic acid chain, enhancing the hydrogel's tensile strength, tensile strength, and other mechanical properties. Under the active metal cathode and inert anode, the hydrogel generates a large amount of hydroxyl radicals through anodic electrolysis. The surface of the hydrogel in contact with the skin, being the inert cathode surface, undergoes oxidation, consuming a large amount of hydroxyl radicals and lowering the pH. This further enhances the chemical interaction of the catechol groups on this surface with the electrostatic attraction of the ionic liquid, increasing viscosity.

[0036] The ionic liquid mainly includes any one or more of [EMIM]Cl, [EMIM]Ac, [EMIM]Br, [BMIM]Cl, [BMIM]Ac, and [BMIM]Br, and is prepared by mixing the ionic liquid with PBS in different mass ratios as a solvent; the olefinic monomer mainly includes any one or more of acrylic acid, butenoic acid, hexenoic acid, and their derivatives; the boric acid monomer mainly includes any one or more of boric acid, sodium borate, phenylboronic acid, and their derivatives; the catechol monomer in the polyaspartic acid-catechol monomer can be any one or more of dopamine, 2-amino-3-(4-hydroxyphenyl)propionic acid, and their derivatives; the initiator can be any one of α-ketoglutarate, Irgacure2959, Irgacure1173, etc.; the crosslinking agent can be any one of N,N'-methylenebisacrylamide, polyethylene glycol (diol) diacrylate, etc.

[0037] The hydrogel achieves viscosity control under the electrolysis of an active metal anode and an inert cathode electric field; the active metal electrode may include any one of metals such as Zn, Fe, Sn, and Pb; the inert electrode may be any one of Pt, Au, graphite, etc.

[0038] The present invention also provides a method for preparing the hydrogel for an electrically controlled viscous electrostimulation electrode as described above, the preparation method mainly comprising the following steps:

[0039] (1) Dissolve 5 mmol-15 mmol of polyaspartic acid in MES solution with pH 4-6, and then degas.

[0040] (2) Add 3-5 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 3-5 mmol of N-hydroxythiosuccinimide to the obtained mixed solution, then mix with magnetic stirring and degas.

[0041] (3) Place 3-5 mmol of catechol monomer in the obtained solution, seal and stir thoroughly for 6 hours, dialyze and freeze dry to obtain polyaspartic acid-catechol monomer.

[0042] (4) Mix the PBS solution with pH=7.4 and the ionic liquid evenly to obtain the hydrogel solvent.

[0043] (5) Dissolve the olefinic monomer, boric monomer, initiator and crosslinking agent in the above solvent, stir magnetically until completely dissolved, add polyaspartic acid-catechol monomer and stir evenly, and after degassing, the pre-crosslinked hydrogel solution can be obtained.

[0044] Please see Figure 2The present invention also provides an electrically controlled viscous electrostimulation electrode, the electrode comprising, from top to bottom, a hydrogel viscous top layer, a flexible base layer 1, a stretchable conductive layer 4, and a hydrogel viscous bottom layer, the hydrogel viscous top layer and the hydrogel viscous bottom layer forming a hydrogel layer 6, the hydrogel layer 6 being prepared using the hydrogel described above. When the electrode is in operation, it is attached to human skin 7 to measure the electromyographic signals of nerve 8. The flexible base layer 1 is made of styrene-butadiene block copolymer, but can also be replaced with any of the stretchable elastomers and their derivatives such as PDMS and Ecoflex; the stretchable conductive layer 4 is made of a stretchable silver-gallium indium alloy conductive material.

[0045] In specific neurological diagnostic applications, the electrically controlled viscous electrostimulation electrode further enhances the electrode's flexibility and stretchability by synthesizing a flexible hydrogel interface, and further improves signal quality and resistance to motion artifacts by incorporating ionic liquids to optimize the conductivity of the electrode / skin interface. The viscous effect of the hydrogel interface mainly includes the chemical bond adhesion of polyaspartic acid-catechol groups and the electrostatic attraction of ionic liquids. The adjustable viscous feature is that, for patients with nerve damage of different ages and different nerve distribution sites, the viscous requirements are different. By changing the direction of the electric field applied to the hydrogel, the voltage, and the electrolysis time, the viscous chemical bonds and electrostatic bonds of the hydrogel at the skin contact surface are broken and recombined to regulate the viscous properties. At the same time, when an active metal is used as the anode during the viscous regulation process, the metal cations diffuse into the hydrogel and form metal coordination bonds with the abundant carboxyl groups in the polyaspartic acid chain, thereby enhancing the mechanical properties of the hydrogel, such as tensile strength and fracture strength.

[0046] In one specific embodiment, please refer to Figure 1 A method for preparing an electrically controlled viscous electrical stimulation electrode for peripheral nerve diagnosis is provided, wherein the preparation of the electrically controlled viscous electrical stimulation electrode includes the following steps:

[0047] (1) The hard substrate was cleaned with acetone, isoacetone and deionized water in sequence, and then the hard substrate was dried with nitrogen.

[0048] (2) Spin-coat the hydrogenated styrene-butadiene block copolymer onto a rigid substrate and wait for the solvent to evaporate completely, and the hydrogenated styrene-butadiene block copolymer will be cured.

[0049] (3) Fix the rigid substrate horizontally on the stage of the screen printing machine, with the side coated with hydrogenated styrene-butadiene block copolymer facing upwards. Then install a screen made of polyvinyl chloride (PVC) material on the screen printing machine, so that the screen is parallel to the rigid substrate and above it. Then adjust the position of the stage so that the projection of the cutout pattern on the screen onto the rigid substrate is within the area enclosed by the outer edge of the rigid substrate.

[0050] (4) Apply silver-gallium indium alloy conductive material (SLM) evenly to the stencil and cover the stencil with the cutout pattern. Then use a scraper to scrape the stencil surface so that the silver-gallium indium alloy conductive material is printed onto the hydrogenated styrene-butadiene block copolymer layer through the cutout pattern on the stencil. Then wait 20-50 minutes until the silver-gallium indium alloy conductive material on the hydrogenated styrene-butadiene block copolymer layer is cured, thereby forming the conductive layer of the electrode.

[0051] (5) The obtained electrode is laser-engraved to create a pattern, and the obtained electrode is peeled off from the hard substrate.

[0052] (6) Prepare a benzophenone:ethanol mass ratio of 1:9 and immerse the resulting electrode substrate in the benzophenone / ethanol solution for a predetermined time, preferably 30 min.

[0053] (7) The obtained electrode is placed in an acrylic container filled with the liquid pre-crosslinked hydrogel solution. A quartz glass plate is used to completely cover the top of the acrylic container, keeping the hydrogenated styrene-butadiene block copolymer layer facing upwards. The container is then placed under ultraviolet light for a predetermined time to obtain a fully polymerized hydrogel adhesive layer as the top layer of the hydrogel. Depending on the type of initiator, in addition to using ultraviolet light to initiate hydrogel polymerization, thermal initiation, redox initiation, etc., can also be used. In this embodiment, a 60W ultraviolet lamp with a wavelength of 365nm is used, and photo-initiated polymerization is carried out for 30-50 minutes to complete the crosslinking of the top layer of the hydrogel.

[0054] (8) Separate the obtained hydrogel electrode from the acrylic container, rinse with sufficient benzophenone solution to remove unbonded residue, and then further remove the benzophenone solution from the surface with paper to obtain the hydrogel electrode.

[0055] (9) The obtained hydrogel electrode is placed in an acrylic container filled with a liquid hydrogel pre-crosslinking solution. A quartz glass plate is used to completely cover the top of the acrylic container, keeping the hydrogenated styrene-butadiene block copolymer layer facing downwards. The container is then placed under ultraviolet light for a predetermined time to obtain a fully polymerized hydrogel adhesive layer as the hydrogel adhesive bottom layer. Depending on the type of initiator, in addition to using ultraviolet light to initiate hydrogel polymerization, thermal initiation, redox initiation, etc., can also be used. In this embodiment, a 60W ultraviolet lamp with a wavelength of 365nm is used, and photo-initiated polymerization is carried out for 30-50 minutes to complete the crosslinking of the hydrogel bottom layer.

[0056] (10) Separate the obtained hydrogel electrode from the acrylic container, rinse with enough deionized water to remove unbonded residue, and then further remove the surface water with paper to obtain an electrically controlled viscous electrostimulation electrode.

[0057] Please see Figure 3 After the conductive layer of the electrode is subjected to tensile force and strain, the gallium indium alloy 401 particles and the micron-sized silver sheet 402 inside the conductive layer still maintain good connection, and it maintains conductivity similar to the initial state under tension.

[0058] Please see Figure 4 The electrode can alter viscosity and enhance mechanical structure through electrolysis of hydrogel. To reduce viscosity, the hydrogel electrode is connected to a zinc electrode and a platinum electrode at both ends. The positive terminal of the power supply is connected to the zinc electrode, and the negative terminal is connected to the platinum electrode. During electrolysis, zinc ions are generated at the anolyte, and hydroxide ions are generated at the catholyte. The pH of the solution increases, causing the borate ester bonds to combine with the catechol groups. This reduces the number of catechol groups binding to the skin surface, decreasing Schiff base reactions and Michael additions with the skin. Simultaneously, more carboxyl groups are converted to carboxylate ions, which react with [EMIM]. + Ion binding weakens the electrostatic coupling with carboxyl groups on the skin surface, resulting in a synergistic effect that reduces viscosity. Simultaneously, the generated zinc ions diffuse and form metal coordination bonds with the carboxyl groups of the polyaspartic acid chains in the hydrogel, thereby enhancing the mechanical properties of the hydrogel.

[0059] The hydrogel electrode is connected to a platinum electrode and a zinc electrode at its two ends, respectively. The positive terminal of the power supply is connected to the platinum electrode, and the negative terminal is connected to the zinc electrode. During electrolysis, anodic electrolysis generates hydroxide ions, and cathodic electrolysis generates hydrogen ions. The pH value of the solution decreases, causing the borate ester bond to break with the catechol group. This results in an increase in the number of catechol groups binding to the skin surface, enhancing the Schiff base reaction and Michael addition with the skin. Simultaneously, more carboxyl groups are converted to carboxyl groups. [EMIM] + The freed substances enhance electrostatic coupling with carboxyl groups on the skin surface, thereby synergistically restoring viscosity.

[0060] Please see Figure 5 The electrode changes its viscosity before and after electrolysis of hydrogel 6. During 10 cycles of electrolysis and recovery, the viscosity of hydrogel 6 can rapidly change from 0.2 kPa to 17 kPa.

[0061] Please see Figure 6 The hydrogel electrodes are attached to the nerves in the hand (radial nerve, median nerve) and the leg (sural nerve, common peroneal nerve) as stimulation electrodes, acquisition electrodes and reference electrodes, respectively, for the diagnosis of neuropathy. For patients with abundant hair on the leg skin, the adhesion is reduced by electrolysis of the hydrogel electrodes to avoid excessive adhesion and tearing of the skin. The patient's nerve abnormalities are analyzed by analyzing the electromyography of the corresponding sensory and motor nerves.

[0062] Please see Figure 7 In the electromyography, the sensory nerve signal 18, proximal motor nerve signal 19, and distal motor nerve signal 20 of normal individuals showed significant differences in amplitude, velocity, and latency parameters compared to the sensory nerve signal 21, proximal motor nerve signal 22, and distal motor nerve signal 23 of patients. This verified the effectiveness of the electrode in neurological diagnosis.

[0063] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydrogel for an electrically controlled viscous electrostimulation electrode, characterized in that: The components of the hydrogel include phosphate buffer, ionic liquid, olefinic monomer, boric monomer and polyaspartic acid-catechol monomer; Acetic acid monomers contain carboxylic acids, which can form hydrogen bonds and electrostatic bonds with the skin; the catechol groups in polyaspartic acid-catechol monomers form chemical bonds, while [EMIM] in ionic liquids... + It can form electrostatic bonds with the skin, thus ensuring the adhesion of the hydrogel.

2. The hydrogel for an electrically controlled viscous electrostimulation electrode as described in claim 1, characterized in that: The hydrogel further includes an initiator and a crosslinking agent, wherein the mass fractions of the olefinic monomer, the boric monomer, the initiator, the crosslinking agent, and the polyaspartic acid-catechol monomer are 15 wt%-25 wt%, 0.5 wt%-2 wt%, 0.01 wt%-0.05 wt%, 0.02 wt%-0.1 wt%, and 2 wt%-5 wt%, respectively; and the mass ratio of the phosphate buffer and the ionic liquid is 1:

1.

3. The hydrogel for electrically controlled viscous electrostimulation electrodes as described in claim 2, characterized in that: The ionic liquid includes any one or more of [EMIM]Cl, [EMIM]Ac, and [EMIM]Br; the olefinic monomers include any one or more of acrylic acid, butenoic acid, hexenoic acid, and their derivatives; the boric acid monomers include any one or more of boric acid, sodium borate, phenylboronic acid, and their derivatives; the catechol monomer in the polyaspartic acid-catechol monomer is any one or more of dopamine, 2-amino-3-(4-hydroxyphenyl)propionic acid, and their derivatives; the initiator is any one of α-ketoglutarate, Irgacure2959, and Irgacure1173; and the crosslinking agent is any one of N,N'-methylenebisacrylamide and polyethylene glycol (diol) diacrylate.

4. The hydrogel for an electrically controlled viscous electrostimulation electrode as described in any one of claims 1-3, characterized in that: The viscosity of the hydrogel is controlled by electrolysis.

5. The hydrogel for an electrically controlled viscous electrostimulation electrode as described in claim 4, characterized in that: The hydrogel achieves viscosity control under the electrolysis of an active metal anode and an inert cathode electric field. The active metal electrode is any one of Zn, Fe, Sn, and Pb; the inert cathode is any one of Pt, Au, and graphite.

6. A method for preparing a hydrogel for an electrically controlled viscous electrostimulation electrode according to any one of claims 1-5, characterized in that: First, a PBS solution with pH=7.4 and an ionic liquid are mixed uniformly to obtain a hydrogel solvent. Then, an olefinic monomer, a boric monomer, an initiator, and a crosslinking agent are dissolved in the hydrogel solvent and magnetically stirred until completely dissolved. Next, a polyaspartic acid-catechol monomer is added and stirred evenly. After degassing, the hydrogel is obtained.

7. The application of the hydrogel for electrically controlled viscous electrical stimulation electrodes according to any one of claims 1-5 in electrically controlled viscous electrical stimulation electrodes, characterized in that: The electrically controlled viscous electrostimulation electrode comprises, from top to bottom, a hydrogel viscous top layer, a flexible base layer, a stretchable conductive layer, and a hydrogel viscous bottom layer. Both the hydrogel viscous top layer and the hydrogel viscous bottom layer are prepared using the hydrogel for electrically controlled viscous electrostimulation electrodes as described in any one of claims 1-5.

8. The application of the hydrogel as described in claim 7 in an electrically controlled viscous electrostimulation electrode, characterized in that: The flexible substrate layer is made of styrene-butadiene block copolymer, PDMS, or Ecoflex; the stretchable conductive layer is made of stretchable silver-gallium indium alloy conductive material.

9. The application of the hydrogel as described in claim 7 in an electrically controlled viscous electrostimulation electrode, characterized in that: The electrode achieves changes in viscosity and enhancement of mechanical structure through electrolysis.

10. The application of the hydrogel as described in claim 9 in an electrically controlled viscous electrostimulation electrode, characterized in that: Connect the two ends of the electrode to a Zn electrode and a Pt electrode respectively. Connect the positive terminal of the power supply to the Zn electrode and the negative terminal of the power supply to the Pt electrode. After electrolysis begins, zinc ions are generated by anodic electrolysis, which form metal coordination bonds with carboxylate ions in the hydrogel, thereby increasing the tensile / fracture strength and decreasing the viscosity of the hydrogel. Alternatively, connect the two ends of the electrode to a Zn electrode and a Pt electrode respectively. Connect the positive terminal of the power supply to the Pt electrode and the negative terminal of the power supply to the Zn electrode. After electrolysis begins, hydroxide ions are generated by anodic electrolysis and hydrogen ions are generated by cathodic electrolysis, thereby increasing the viscosity.

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