Electrochemical method for loading adhesion high molecular on electrode surface and application

Abstract

The application discloses an electrochemical method for loading adhesive polymer on the surface of an electrode and application, and the method comprises the following steps: sequentially performing cyclic voltammetry and constant potential method to realize rapid and patterned loading of the adhesive layer, and the method has the characteristics of flexible and simple operation, wide application range and repeatability. The flexible array electrode modified by the electrochemical method provided by the application only obtains the adhesive layer at the conductive part, so that the electrode has excellent adhesive performance, is more attached to human skin, and the stability of the skin-electrode interface is enhanced; when the electrode is attached to the skin for impedance testing, the skin interface impedance is lower than that of a commercial gel electrode, and the monitored electrophysiological signal is stable and accurate, meanwhile, the patterned loading characteristic can effectively prevent short circuit and signal crosstalk. The electrochemical method provided by the application is used as a modification technology, which is general and simple for electrophysiological sensors, and is of great significance for reducing the cost and improving the performance of wearable health monitoring devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry, in particular to an electrochemical method for loading adhesive polymer on the surface of an electrode and application thereof. BACKGROUND

[0002] Electrophysiological sensors (electrodes) are used to collect complex electrophysiological signals, providing rich information about the body condition. Reliable signal acquisition requires a stable skin-electrode interface to prevent adverse effects caused by interface changes. Although the introduction of conductive glue layers enhances the stability of the interface to some extent, in the application scenario of array electrodes, the mutual contact between the conductive glue layers can easily cause short circuit and signal crosstalk problems.

[0003] In view of this technical problem of array electrodes, current research has explored several solutions, but all have limitations. For example, simply relying on adhesive tape or other adhesive materials to externally fix the electrodes on the skin may not be able to ensure a stable connection, especially when the skin undergoes significant deformation. Another method is to manually add gel on the surface of each sensing point of the array electrode to enhance contact with the skin. However, this method is not ideal for high-density and small-size array electrodes. These solutions are lacking in convenience and universality, and therefore, there is an urgent need to develop a method that can autonomously and selectively load adhesive layers. SUMMARY

[0004] To solve the above technical problems, the purpose of the present application is to provide an electrochemical method for loading adhesive polymer on the surface of an electrode and application thereof. Sequentially performing cyclic voltammetry (CV) and constant potential method (FP) can achieve rapid and patterned loading of the adhesive layer. This method has the characteristics of flexible and simple operation, wide application range, and repeatability. The electrode modified by the electrochemical method has good adhesive performance and low skin interface impedance, and is stable and accurate when used for monitoring electrophysiological signals.

[0005] The present application is realized by the following technical solutions:

[0006] The present application provides an electrochemical method for loading adhesive polymer on the surface of an electrode in the first aspect, comprising the following steps:

[0007] Under an inert gas environment, an electrochemical workstation with a three-electrode system is used to sequentially perform cyclic voltammetry (CV) and constant potential method (FP) to load adhesive polymer on the surface of the working electrode, obtaining an electrode modified by the electrochemical method;

[0008] The electrochemical workstation comprises an electrochemical instrument, an electrolytic cell, a working electrode, a counter electrode, a reference electrode and an electrolyte, the working electrode is a metal electrode or an array electrode, the metal electrode is a copper (Cu) electrode or a titanium (Ti) electrode, the array electrode is an array electrode containing copper and / or titanium, and the electrolyte comprises an imidazole ionic liquid, butyl acrylate (BA, ), an initiator, a chlorinated salt and an organic solvent; when the working electrode contains copper, the initiator is 4-bromo-diazobenzene tetrafluoroborate (BBD, ); when the working electrode contains titanium, the initiator is 4-bromo-diazobenzene tetrafluoroborate and 4-nitro-diazobenzene tetrafluoroborate (NBD, ).

[0009] The electrochemical method (cyclic voltammetry and constant potential method) provided by the application can quickly and regionally modify a metal electrode or a flexible array electrode, realizes rapid and patterned loading of an adhesive layer, and the operation device is rationally designed and simple to assemble. The cyclic voltammetry (CV) and the constant potential method (FP) are used for electrochemical control of polymerization and grafting reaction on a conductive surface, and the significant conductivity difference between a sensing point of the flexible array electrode and a base material provides a theoretical basis for selective loading of the polymer adhesive layer.

[0010] The thickness of the adhesive polymer (adhesive layer) loaded on the surface of the working electrode is in the micron level, wherein the butyl acrylate monomer provides adhesion, and the functional groups of the introduced ionic liquid provide sufficient conductivity, so that the metal part (i.e. functional site, sensing point) of the metal electrode or the flexible array electrode is endowed with adhesion, can be repeatedly used and stored for a long time.

[0011] Further, the array electrode is obtained by using electroplating method to pattern etch a polyimide (PI) film.

[0012] Further, the electrolytic cell comprises a closed cover and an inlet and outlet gas pipe.

[0013] Further, the working electrode (WE) is a copper sheet, a titanium sheet or a flexible array electrode, the counter electrode (CE) is a platinum wire electrode, and the reference electrode (RE) is a silver / silver chloride electrode.

[0014] Further, the imidazole ionic liquid is 1-ethyl-3-methyl imidazole tetrafluoroborate (ILB, ) and / or 1-ethyl-3-methyl imidazoline bis(trifluoromethylsulfonyl) imide (ILN, ). The imidazole ionic liquid provides ionic conductivity of the electrolyte.

[0015] Further, the concentration of the imidazole ionic liquid in the electrolyte is 0.1-0.3 mol / L.

[0016] Further, the volume of the butyl acrylate accounts for 45-55% of the volume of the electrolyte.

[0017] Further, the chlorinated salt is potassium chloride (KCl) and / or sodium chloride (NaCl).

[0018] Further, the organic solvent can be N,N-dimethylformamide (DMF, ).

[0019] Further, the concentration of the initiator in the electrolyte is 15-25 mg / mL.

[0020] Further, the electrolyte further comprises a vinyl-based ionic liquid.

[0021] Further, the vinyl-based ionic liquid is selected from one or more of 1-vinyl-3-ethylimidazole tetrafluoroborate (M1, ), 1-vinyl-3-butylimidazole tetrafluoroborate (M2, ), 1-vinyl-3-ethylimidazole trifluoromethanesulfonimide salt (M3, ), and 1-vinyl-3-butylimidazole trifluoromethanesulfonimide salt (M4, ).

[0022] Further, the volume ratio of the butyl acrylate and the vinyl-based ionic liquid is 1:(1-2).

[0023] Further, the total volume of the butyl acrylate and the vinyl-based ionic liquid accounts for 45-55% of the volume of the electrolyte.

[0024] Further, the cyclic voltammetry is used to electrochemically reduce the diazonium salt to obtain the phenyl radical.

[0025] In the specific embodiment, the electrochemical working station is used to perform a pre-scan (cyclic voltammetry, scan rate of 0.1-0.2 V·s -1 , one cycle, vs RE) in an inert environment to obtain the initiation characteristics and electrochemical curve of the initiator, according to the electrochemical curve, the reduction peak position range is determined, and a low-rate scan (cyclic voltammetry, scan rate of 0.01-0.02 V·s -1 , multiple cycles, vs RE) is performed.

[0026] Further, during the performance of the constant potential method, the phenyl radical induces the polymerization and chain entanglement of the monomer.

[0027] In the specific embodiment, a suitable potential (corresponding to the potential at the end of the reduction peak in the last cycle of cyclic voltammetry) is selected for constant reduction potential treatment (constant potential method, 1-4 hours, vs RE).

[0028] In the specific embodiment, after the reaction is completed, the working electrode is taken out, the surface is rinsed and dried to obtain the electrochemically modified metal electrode or flexible array electrode.

[0029] Further, the inert gas can be nitrogen, argon or the like, and the electrochemical modification is only carried out in an inert environment to achieve effective loading of the adhesion layer.

[0030] In the specific embodiment, after the electrolyte is prepared, the inert gas is continuously blown into the electrolytic cell to discharge oxygen (20-30 minutes), and then the gas circuit is sealed to maintain the inert environment in the electrolytic cell.

[0031] In the specific embodiment, the two steps (cyclic voltammetry and constant potential method) of the electrochemical modification provided by the application need to be carried out in sequence to achieve effective loading of the adhesion layer, and only one of the steps cannot achieve effective loading.

[0032] In the specific embodiment, the adhesion layer of the electrochemically modified electrode provided by the application is more or less damaged after use, but the remaining adhesion layer can still be used; if the adhesion layer is invalid after multiple uses, the adhesion layer can be cleaned with ethanol, and the adhesion layer can be obtained again by secondary modification.

[0033] The second aspect of the application provides an electrochemically modified electrode prepared by the electrochemical method of the first aspect.

[0034] The third aspect of the application provides an application of the electrochemically modified electrode of the second aspect in electrophysiological signal acquisition.

[0035] The flexible array electrode electrochemically modified by the application only obtains an adhesion layer at the sensing point, and when the electrode is attached to the skin for impedance test, the skin interface impedance is greatly reduced and is lower than that of a commercial gel electrode; at the same time, the flexible array electrode electrochemically modified by the application can stably and accurately measure electrocardiogram (ECG) and electromyogram (EMG), and effectively avoid signal crosstalk between sub-electrode sensing points.

[0036] The application has the following beneficial effects:

[0037] The application provides an electrochemical method for loading adhesive high molecules on the surface of an electrode, can selectively load adhesive high molecules on the surface area of a flexible array electrode, solves the problems in the prior art, and realizes rapid and patterned loading of the adhesive layer by sequentially performing two steps of cyclic voltammetry and constant potential method.

[0038] The flexible array electrode modified by the electrochemical method provided by the application only obtains an adhesive layer at the conductive part, so that the electrode has excellent adhesive performance, is more attached to human skin, and enhances the stability of the skin-electrode interface; when the electrode is attached to the skin for impedance testing, the skin interface impedance is lower than that of a commercial gel electrode, and the monitored electrophysiological signal is stable and accurate, and meanwhile, the patterned loading feature can effectively prevent short circuit and signal crosstalk.

[0039] The electrochemical method provided by the application is expected to be applied to more complex electrode systems, such as stretchable electrodes, microelectrode arrays and breathable electrodes, and become a universal patterning strategy to solve the problems of breathability of the skin electrode and signal crosstalk in the array electrode. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A schematic diagram of an electrolytic cell device used in the application.

[0041] Figure 2 A reaction flow diagram of the electrochemical method provided by the application.

[0042] Figure 3 A schematic diagram of a flexible array electrode before and after electrochemical method modification.

[0043] Figure 4 A real object diagram of the flexible array electrode containing copper in Example 1 and a micro-morphology diagram after electrochemical method modification; wherein (a) is a real object diagram of the flexible array electrode containing copper, and (b) is a scanning electron microscope diagram of the flexible array electrode modified by the electrochemical method in Example 1.

[0044] Figure 5 A metal sheet and PDMS lap shear strength diagram and a real object diagram of the flexible array electrode modified by the electrochemical method in Example 4, 5 and Comparative Examples 5, 6; wherein (a) is a metal electrode and PDMS lap shear strength diagram of the flexible array electrode modified by the electrochemical method in Example 4, 5 and Comparative Examples 5, 6, and (b) is a real object diagram of the metal electrode modified by the electrochemical method in Example 5 and Comparative Examples 5, 6.

[0045] Figure 6 The image shows the overlap shear strength of copolymers obtained by uniformly coating two sheets of PDMS with four vinyl ionic liquids (M1 / M2 / M3 / M4) and butyl acrylate (BA) under thermal initiation of azobisisobutyronitrile (AIBN).

[0046] Figure 7 Skin interfacial impedance diagrams of the electrochemically modified flexible array electrode, the unmodified flexible array electrode (fixed with tape), and the commercial gel electrode obtained in Examples 1-3.

[0047] Figure 8 The diagram shows the electrochemically modified flexible array electrode (electrochemically modified electrode), the unmodified flexible array electrode (electrode fixed with tape), and the commercially available gel-modified flexible array electrode (commercially available gel-modified electrode) used to measure electrocardiogram (ECG) signals, and the measured ECGs. Among them, (a) is a schematic diagram of the electrode being attached to a person's chest to measure ECG signals, and (b) is a schematic diagram of the measured ECG and the signal crosstalk that occurred during the commercial gel-doping process.

[0048] Figure 9 The diagram shows the electromyography (EMG) of the flexible array electrode modified by electrochemical method (electrochemically modified electrode), the flexible array electrode not modified by electrochemical method (electrode fixed with tape), and the flexible array electrode modified by commercial gel dotting (commercial gel dotting modified electrode) obtained in Example 3. Among them, (a) is a schematic diagram of the electrode being attached to a person's arm for measuring EMG signals, and (b) is the measured EMG and a schematic diagram of signal crosstalk during the commercial gel dotting process. Detailed Implementation

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0050] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0051] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0052] The application provides an electrochemical method for loading adhesive macromolecules on the surface of an electrode, comprising the following steps:

[0053] In an inert gas environment, the electrochemical workstation with a three-electrode system is used to sequentially perform cyclic voltammetry (CV) and constant potential method (FP) to load adhesive macromolecules on the surface of the working electrode, so as to obtain an electrode modified by the electrochemical method.

[0054] The electrochemical workstation comprises an electrochemical instrument, an electrolytic cell, a working electrode, a counter electrode, a reference electrode and an electrolyte, the working electrode is a metal electrode or an array electrode, the metal electrode is a copper (Cu) electrode or a titanium (Ti) electrode, the array electrode is an array electrode containing copper and / or titanium, and the electrolyte comprises an imidazole ionic liquid, butyl acrylate (BA, ), an initiator, a chlorinated salt and an organic solvent; when the working electrode contains copper, the initiator is 4-bromobenzene diazonium tetrafluoroborate (BBD, ); when the working electrode contains titanium, the initiator is 4-bromobenzene diazonium tetrafluoroborate and 4-nitrobenzene diazonium tetrafluoroborate (NBD, ).

[0055] Preferably, the electrolytic cell is a three-electrode electrochemical electrolytic cell, which comprises a closed cover and an inlet and outlet pipe, and the electrolytic cell device is as shown in Figure 1 The brand, model and the like of other devices are not specifically required and specially limited.

[0056] In the specific embodiment, the working electrode (WE) is a copper sheet, a titanium sheet or a flexible array electrode, the counter electrode (CE) is a platinum wire electrode, and the reference electrode (RE) is a self-prepared silver / silver chloride electrode. The specifications and purity of the metal sheet, the brand and purity of the platinum wire electrode are not specifically required and specially limited.

[0057] Preferably, the flexible array electrode is a PI electrode of 17 or 35 μm thick copper, which is obtained by using an electroplating method for patterned etching. The pattern of the flexible array electrode can be changed for the convenience of practical application and has no special meaning.

[0058] In the specific embodiment, the first step of the electrochemical method is cyclic voltammetry, that is, multi-cycle (ten cycles) and low-rate (0.01-0.02 V s -1 Under electrochemical reduction, the phenyl radical obtained by reduction of the initiator is combined with the metal, and the radical produces an initiation site on the grafting group by absorbing a hydrogen atom, and then a thin dendritic polymer layer (nanoscale) is grafted on the surface of the metal. Generally, a pre-scan (0.1-0.2 V s -1The potential range in which the reduction peak appears (corresponding to the reaction of phenyl diazonium salt reducing to produce phenyl radicals) was determined. Then, a low-rate scan was performed within the selected voltage range. In the later cycles, the reduction peak was observed to shift towards the lower voltage region, due to the increased resistance of the grafted polymer.

[0059] In a specific embodiment, the second step of the electrochemical method is potentiostatic (FP) treatment, which involves a prolonged period of treatment at a fixed reduction potential. Generally, the voltage corresponding to the end of the reduction peak in the last low-rate scan cycle is selected for a prolonged (1-4 h) constant reduction potential treatment. In this step, the main reaction is the polymerization of monomers in the solution near the cathode. As the FP time increases, the current decreases, indicating that the polymer grown on the cathode surface leads to an increase in resistance. During FP polymerization, the chain entanglement between the polymer in the solution and the grafted chains results in a significant increase in the thickness of the grafted polymer layer, reaching the micrometer level.

[0060] Figure 2 The reaction flow diagram of the electrochemical method provided by the present invention is as follows: Figure 3 This is a schematic diagram showing the flexible array electrode before and after electrochemical modification.

[0061] This invention uses an electrochemical method to modify the patterning of the metal sheet or flexible array electrode adhesive layer by performing cyclic voltammetry and potentiostatic method in sequence, selectively modifying the micron-thick conductive adhesive layer region onto the sensing point of the flexible array electrode.

[0062] In the following examples and comparative examples, the silver / silver chloride electrodes were prepared by the following method: by electrochemical etching, wherein the working electrode (WE) was a silver wire; the counter electrode (CE) was a platinum wire electrode; the reference electrode (RE) was a commercially available silver / silver chloride electrode; the electrolyte was a 1 mol / L hydrochloric acid solution; the working electrode silver wire was subjected to electrochemical potentiostatic etching to become a self-made silver / silver chloride electrode, wherein the voltage was 0.5 V and the time was 30 s.

[0063] Example 1

[0064] An electrochemical method for loading adhesive polymers onto the surface of a flexible array electrode containing copper includes the following steps:

[0065] (1) Preparation of electrolyte: The solvent is a DMF solution containing saturated KCl. Add 0.1 mol / L ILB to it, add BA as monomer (monomer volume accounts for 50% of the total solution volume), and finally add 20 mg / mL BBD as initiator.

[0066] (2) A flexible array electrode is used as the working electrode, a Pt wire electrode is used as the counter electrode, and a self-made silver / silver chloride electrode is used as the reference electrode. The electrodes are installed in a closed electrolytic cell. Oxygen is discharged by continuously blowing N2 into the closed electrolytic cell (20 minutes). Then the gas path is sealed to maintain an inert gas environment in the electrolytic cell.

[0067] (3) A pre-scan was performed using cyclic voltammetry on an electrochemical workstation, at 0.1 V s. -1 One cycle, locking the position of the reduction peak, and performing low-rate cyclic voltammetry, 0.01 V / s. -1 Ten cycles.

[0068] (4) After the cyclic voltammetry is completed, select the potential corresponding to the end of the reduction peak in the last cycle and perform constant potential method for 2 hours.

[0069] (5) After the potentiostatic method is completed, the flexible array electrode is removed, its surface is rinsed with ethanol and dried to obtain the flexible array electrode modified by electrochemical method.

[0070] Figure 4 The images show the physical image of the flexible array electrode containing copper in Example 1 and the microstructure image after electrochemical modification. (a) is a physical image of the flexible array electrode containing copper, and (b) is a scanning electron microscope image of the flexible array electrode modified by electrochemical method obtained in Example 1. The microstructure of the adhesion layer on the surface of the flexible array electrode can be clearly observed under a scanning electron microscope.

[0071] Example 2

[0072] An electrochemical method for loading adhesive polymers onto the surface of a flexible array electrode containing copper is basically the same as the electrochemical method in Example 1, except that in step (1), 0.1 mol / L ILB is replaced with 0.1 mol / L ILN; the monomers are BA and M4, with a volume ratio of 1:1, and the total volume of the monomers accounts for 50% of the total volume of the solution.

[0073] Example 3

[0074] An electrochemical method for loading adhesive polymers onto the surface of a flexible array electrode containing copper is basically the same as the electrochemical method in Example 1, except that in step (1), 0.1 mol / L ILB is replaced with 0.1 mol / L ILN; the monomers are BA and M4, with a volume ratio of 1:2, and the total volume of the monomers accounts for 50% of the total volume of the solution.

[0075] Example 4

[0076] An electrochemical method for loading adhesive polymers onto the surface of a Ti sheet includes the following steps:

[0077] (1) Preparation of electrolyte: The solvent is a DMF solution containing saturated KCl. Add 0.1 mol / L ILB to it, add BA as monomer (monomer volume accounts for 50% of the total solution volume), and finally add 10 mg / mL BBD and 10 mg / mL NBD as initiators.

[0078] (2) Using a Ti sheet as the working electrode, a Pt wire electrode as the counter electrode, and a self-made silver / silver chloride electrode as the reference electrode, the electrodes were installed in a sealed electrolytic cell. Oxygen was vented by continuously blowing N2 into the sealed electrolytic cell (20 minutes), and then the gas path was sealed to maintain an inert gas environment in the electrolytic cell.

[0079] (3) A pre-scan was performed using cyclic voltammetry on an electrochemical workstation, at 0.1 V s. -1 One cycle, locking the position of the reduction peak, and performing low-rate cyclic voltammetry, 0.01 V / s. -1 Ten cycles.

[0080] (4) After the cyclic voltammetry is completed, select the potential corresponding to the end of the reduction peak in the last cycle and perform constant potential method for 2 hours.

[0081] (5) After the potentiostatic method is completed, the Ti sheet is removed, its surface is rinsed with ethanol and dried to obtain the Ti electrode modified by electrochemical method.

[0082] Example 5

[0083] An electrochemical method for loading adhesive polymers onto the surface of Cu sheets includes the following steps:

[0084] (1) Preparation of electrolyte: The solvent is a DMF solution containing saturated KCl. Add 0.1 mol / L ILB to it, add BA as monomer (monomer volume accounts for 50% of the total solution volume), and finally add 20 mg / mL BBD as initiator.

[0085] (2) Using Cu sheet as working electrode, Pt wire electrode as counter electrode, and self-made silver / silver chloride electrode as reference electrode, the electrodes are installed in a closed electrolytic cell. Oxygen is discharged by continuously blowing N2 into the closed electrolytic cell (20 minutes), and then the gas path is sealed to maintain an inert gas environment in the electrolytic cell.

[0086] (3) A pre-scan was performed using cyclic voltammetry on an electrochemical workstation, at 0.1 V s. -1 One cycle, locking the position of the reduction peak, and performing low-rate cyclic voltammetry, 0.01 V / s. -1 Ten cycles.

[0087] (4) After the cyclic voltammetry is completed, select the potential corresponding to the end of the reduction peak in the last cycle and perform constant potential method for 2 hours.

[0088] (5) After the potentiostatic method is completed, the Cu sheet is removed, its surface is rinsed with ethanol and dried to obtain the Cu electrode modified by electrochemical method.

[0089] Comparative Example 1

[0090] An electrochemical method for loading adhesive polymers onto the surface of a flexible array electrode containing copper is basically the same as the electrochemical method in Example 1, except that in step (1), 20 mg / mL BBD is replaced with 20 mg / mL NBD.

[0091] Comparative Example 2

[0092] An electrochemical method for loading adhesive polymers onto the surface of a flexible array electrode containing copper is basically the same as the electrochemical method in Example 1, except that in step (1), 20 mg / mL BBD is replaced with 10 mg / mL BBD and 10 mg / mL NBD.

[0093] Comparative Example 3

[0094] An electrochemical method for loading adhesive polymers onto the surface of a Ti sheet is basically the same as the electrochemical method in Example 4, except that in step (1), 10 mg / mL BBD and 10 mg / mL NBD are replaced with 20 mg / mL BBD.

[0095] Comparative Example 4

[0096] An electrochemical method for loading adhesive polymers onto the surface of Ti sheets is basically the same as the electrochemical method in Example 4, except that in step (1), 10 mg / mL BBD and 10 mg / mL NBD are replaced with 20 mg / mL NBD.

[0097] Comparative Example 5

[0098] An electrochemical method for loading adhesive polymers onto the surface of Cu sheets is basically the same as the electrochemical method in Example 5, except that the potentiostatic method of step (4) is not performed.

[0099] Comparative Example 6

[0100] An electrochemical method for loading adhesive polymers onto the surface of Cu sheets is basically the same as the electrochemical method in Example 5, except that the cyclic voltammetry method of step (3) is not performed.

[0101] The electrodes modified by the electrochemical method obtained in Examples 1-4 and Comparative Examples 1-4 were subjected to viscosity tests. The test method was as follows: weighing paper was pressed onto the electrochemically modified electrode; if the electrode did not fall off when the weighing paper was lifted, the result was considered viscous. The test results are shown in Table 1:

[0102] Table 1

[0103]

[0104]

[0105] Shear strength was tested in tensile mode using a universal testing machine at a shear rate of 60 mm / min on an electrochemically modified metal sheet bonded to a polydimethylsiloxane film (PDMS).

[0106] Figure 5 The images show the shear strength diagrams and physical images of the electrochemically modified metal sheets and PDMS obtained in Examples 4, 5, and Comparative Examples 5, 6; wherein, (a) is the shear strength diagram of the electrochemically modified metal electrode and PDMS obtained in Examples 4, 5, and Comparative Examples 5, 6, and (b) is a physical image of the electrochemically modified metal electrode obtained in Examples 5 and Comparative Examples 5, 6. Figure 5 As can be seen in (a), the overlap shear strength between the electrochemically modified Cu sheet and the PDMS film is approximately 3.03 kPa, while that between the electrochemically modified Ti sheet and the PDMS film is approximately 5.22 kPa. From... Figure 5 As shown in Figure (b), the growth of the metal sheet surface modified by the electrochemical method can be observed. When only CV is performed, no adhesion layer grows on the metal sheet surface, and it is not sticky. When only FP is performed, the adhesion layer does not grow on the metal sheet surface and falls off into the solution. After CV and FP are performed, an adhesion layer is obviously grown on the metal sheet surface, and it is sticky.

[0107] Figure 6 The image shows the overlap shear strength of copolymers obtained by uniformly coating two sheets of PDMS with four vinyl ionic liquids (M1 / M2 / M3 / M4) and butyl acrylate (BA) under thermal initiation of azobisisobutyronitrile (AIBN).

[0108] Skin interfacial impedance was measured using a controlled potential EIS (impedance technique) on an electrochemical workstation, ranging from 10 kHz to 10 Hz with an amplitude of 0.2 V RMS. Electrochemical impedance spectroscopy was performed on a flexible array electrode modified by electrochemical methods, where the center-to-center distance between the two main working sub-electrodes was approximately 1.6 cm, and the skin contact area of ​​each sub-electrode was approximately 0.2 cm². 2In contrast, commercial gel electrodes have a contact area of ​​0.785 cm² per electrode with the skin. 2 The distance between the two commercial gel electrodes is approximately 1.6 cm.

[0109] Figure 7 The images show the skin interfacial impedance of the electrochemically modified flexible array electrode, the unmodified flexible array electrode (fixed with tape), and the commercial gel electrode obtained in Examples 1-3. Figure 7 As can be seen, the skin interface impedance of the flexible array electrode modified by electrochemical method is significantly reduced. Over a wide frequency range, the skin interface impedance per unit area of ​​the flexible array electrode modified by electrochemical method is better than that of commercial gel electrodes.

[0110] The electrochemically modified flexible array electrode obtained in Example 3 (electrochemically modified electrode), the unmodified flexible array electrode (electrode fixed with tape), and the commercially available gel-coated modified electrode (commercially available gel-coated modified electrode) were used to measure electrocardiogram (ECG) and electromyogram (EMG) signals. The ECG and EMG signals were recorded using a Backyard Brains Spiker Box with three electrodes. The signal-to-noise ratio of the flexible array electrode coated with commercially available gel was 11.01 dB, and the signal-to-noise ratio of the electrochemically modified flexible array electrode was 11.69 dB.

[0111] Figure 8 The diagram shows the electrochemically modified flexible array electrode obtained in Example 3, the unmodified flexible array electrode (fixed with tape), and the commercially available gel-modified flexible array electrode used to measure electrocardiogram (ECG) signals, and the measured ECGs. Among them, (a) is a schematic diagram of the electrode being attached to a person's chest to measure ECG signals, and (b) is a schematic diagram of the measured ECG and the signal crosstalk that occurred during the commercial gel application process.

[0112] Figure 9 The diagram shows the electromyography (EMG) of the flexible array electrode modified by electrochemical method obtained in Example 3, the flexible array electrode without electrochemical modification (fixed with tape), and the flexible array electrode modified by commercial gel application; wherein, (a) is a schematic diagram of the electrode being attached to a person's arm for measuring EMG signals, and (b) is the measured EMG and a schematic diagram of signal crosstalk during the commercial gel application process.

[0113] from Figure 8 and Figure 9As can be seen, the flexible array electrode modified by the electrochemical method can stably and accurately measure electrocardiogram and electromyography signals. The measured electrophysiological signals are not only comparable to those of the flexible array electrode modified by commercial adhesive dotting, but also effectively avoid signal crosstalk between sub-electrode sensing points during the dotting process.

[0114] In summary, this invention provides an electrochemical method for selectively loading adhesive polymers onto the surface of a flexible electrode. Utilizing the conductivity difference between the sensing points of the flexible electrode and the substrate material, in-situ electrochemical reactions achieve regionally selective loading of adhesive and ion-conductive polymers, thereby realizing the patterning of the adhesive layer. The electrochemical method provided by this invention requires two sequential steps (CV and FP) to achieve rapid and selective modification of the electrode surface. The resulting adhesive layer thickness is on the micrometer scale. In the modified adhesive layer system, butyl acrylate monomers provide viscosity, while the functional groups of the introduced ionic liquid provide sufficient conductivity.

[0115] The flexible array electrode modified by the electrochemical method provided by this invention has an effective adhesive layer loaded only at the sensing points, thereby improving the stability of the skin-electrode interface and the quality of electrophysiological signal acquisition, and effectively avoiding signal crosstalk between sensing points of the flexible array electrode. Furthermore, the flexible electrode modified by this electrochemical method can be reused and stored for a long time without degradation of the adhesive layer performance. Even if the adhesive layer fails, it can be washed off for secondary modification. This electrochemical modification method is also applicable to the construction of adhesive layers on metal sheets (such as Cu or Ti). The electrochemical method for selectively loading adhesive polymers onto the surface region of flexible electrodes provided by this invention is applicable to both metal sheets and flexible array electrodes, and features a reasonable reaction device design, simple operation, wide applicability, repeatability, low modification cost, and high success rate.

[0116] The electrochemical method provided by this invention is expected to be extended to more complex electrode systems, such as stretchable electrodes, microelectrode arrays, and breathable electrodes, becoming a general patterning strategy to solve the problems of breathability of skin electrodes and signal crosstalk in array electrodes.

[0117] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. 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 claims of the present invention.

Claims

1. An electrochemical method for loading an electrode surface with an adhesive polymer, characterized by, The method comprises the following steps: The electrode is prepared by the electrochemical method as claimed in any one of claims 1-8. The electrochemical workstation comprises an electrochemical instrument, an electrolytic cell, a working electrode, a counter electrode, a reference electrode and an electrolyte, the working electrode is a metal electrode or an array electrode, the metal electrode is a copper electrode or a titanium electrode, the array electrode is an array electrode containing copper and / or titanium, and the electrolyte comprises an imidazole ionic liquid, butyl acrylate, an initiator, a chloride salt and an organic solvent; when the working electrode contains copper, the initiator is 4-bromo-diazonium benzene tetrafluoroborate; when the working electrode contains titanium, the initiator is 4-bromo-diazonium benzene tetrafluoroborate and 4-nitro-diazonium benzene tetrafluoroborate.

2. The electrochemical method according to claim 1, characterized in that, The imidazole ionic liquid is 1-ethyl-3-methyl imidazole tetrafluoroborate and / or 1-ethyl-3-methyl imidazoline bis(trifluoromethylsulfonyl) imide.

3. The electrochemical method of claim 1, wherein, The concentration of the imidazole ionic liquid in the electrolyte is 0.1-0.3 mol / L.

4. The electrochemical method of claim 1, wherein, The electrolyte further comprises a vinyl ionic liquid.

5. The electrochemical method according to claim 4, characterized in that, The vinyl ionic liquid is selected from one or more of 1-vinyl-3-ethyl imidazole tetrafluoroborate, 1-vinyl-3-butyl imidazole tetrafluoroborate, 1-vinyl-3-ethyl imidazole trifluoromethanesulfonylimide salt and 1-vinyl-3-butyl imidazole trifluoromethanesulfonylimide salt.

6. The electrochemical method of claim 4, wherein, The total volume of the butyl acrylate and the vinyl ionic liquid accounts for 45-55% of the volume of the electrolyte.

7. The electrochemical method of claim 1, wherein, The specific operation of the cyclic voltammetry is: pre-scanning for one cycle at a scanning rate of 0.1-0.2V·s -1 , and scanning for multiple cycles at a scanning rate of 0.01-0.02V·s -1 after determining the reduction peak position.

8. The electrochemical method according to claim 7, characterized in that, The specific operation of the constant potential method is that the constant reduction potential treatment is performed at the potential at the end of the reduction peak in the last cycle of the cyclic voltammetry.

9. An electrochemically modified electrode, characterized in that, The electrode is prepared by the electrochemical method as claimed in any one of claims 1-8.

10. The electrode prepared by the electrochemical method as claimed in claim 9 is applied in the collection of electrophysiological signals.

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