Preparation process of flexible stretchable surface electromyography motion sensing integrated electrode

Abstract

The invention discloses a preparation process of a flexible stretchable surface electromyographic motion sensing integrated electrode, and particularly relates to the field of flexible electronic technology and biomedical engineering.The electrode adopts thermoplastic polyurethane or polydimethylsiloxane as a substrate material, and conductivity and fatigue resistance are improved through doping of graphene quantum dots. The electrode comprises a myoelectricity sensing layer and a motion sensing layer, wherein the myoelectricity sensing layer is constructed through electrostatic spinning of a TPU nanofiber net and spraying of liquid metal, and the motion sensing layer forms a snakelike microcrack structure through silk-screen printing of a silver nanowire / TPU mixed material. The honeycomb-shaped insulating layer is used for isolating bimodal signals, and long-acting antibiosis and air permeability are achieved in combination with the self-repairing adhesion layer. After packaging, a Bluetooth 5.0 chip and a miniature lithium battery are integrated, and wireless signal transmission is supported.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flexible electronics and biomedical engineering, in particular to a preparation process of a flexible stretchable surface electromyography motion sensor integrated electrode. BACKGROUND

[0002] Surface electromyography (sEMG) signals play a key role in the home rehabilitation of stroke patients as an important means of evaluating muscle activity and neural control. Traditional electrodes (such as Ag / AgCl wet electrodes) rely on conductive gel, which can easily cause skin allergies and poor signal stability, while implantable electrodes require surgery and are expensive. In recent years, flexible stretchable electrodes have become a research hotspot, which realizes dynamic skin fitting and reduces motion artifacts through material innovation (such as liquid metal, conductive polymer) and structural design (such as bionic "fishing net" microstructure), providing a new direction for motion recognition and evaluation in the home rehabilitation scenario.

[0003] Existing technologies focus on the conductive materials, structural optimization and multi-modal integration of flexible electrodes, including: first, combining liquid metal with elastic polymer, through the design of "fishing net" microstructure, realizing low sheet resistance of 52 mΩ / sq and high stability of resistance change of only 5% after 330,000 stretching cycles, suitable for wireless signal transmission under dynamic deformation. Second, based on the adhesion layer of dynamic hydrogen bond material and the structure of electrospun porous fibers, high-strength skin adhesion, room temperature self-repairing and sweat-permeable heat dissipation functions are realized, which can alleviate the inflammation caused by long-term wearing. Third, through the design of polyimide microneedle and snake-shaped interconnection structure, a microneedle electrode array is realized, which has a stretchability of 60%-90% and can accurately collect intramuscular electrical signals, but requires a complex laser micromachining process.

[0004] However, the existing technology still faces the following core challenges: First, there are bio-compatibility and safety hazards, carbon-based conductive materials have potential skin toxicity, liquid metal may leak after long-term contact, and the bio-compatibility of self-repairing materials is not verified. Second, there are problems of multi-modal signal interference and insufficient long-term stability, the coupling noise between the electromyography and motion sensor layers causes signal crosstalk, and the conductive network is easy to break under dynamic stretching or sweat environment, resulting in a significant decrease in signal stability. Finally, there is a contradiction between algorithm adaptability and wearing comfort, the existing model has low real-time processing efficiency for high-density array data, and the pursuit of high-precision packaging sacrifices the breathability, which can easily cause skin inflammation in long-term wearing. SUMMARY

[0005] Therefore, the present application provides a preparation process of a flexible stretchable surface electromyography motion sensor integrated electrode to solve the problems raised in the background art.

[0006] In order to achieve the above object, the present application provides the following technical scheme: the preparation process of a flexible stretchable surface electromyography motion sensor integrated electrode, comprising the following preparation steps:

[0007] a) flexible substrate preparation: the electrode substrate material is made into a solution and then spin-coated on a glass substrate, the glass substrate spin-coated with the solution is frozen and dried, and the flexible substrate is obtained after demolding after drying;

[0008] b) electrode preparation: the double-mode sensing layer composed of the electromyography sensing layer and the motion sensing layer is distributed on the front surface of the flexible substrate obtained in step a), the electromyography sensing layer is prepared by sequentially depositing TPU fiber mesh, spraying liquid metal and conductive path on the flexible substrate; the motion sensing layer is prepared by screen printing the mixed material of silver nanowire and TPU on the surface of the substrate, and then heat curing;

[0009] The flexible substrate, the electromyography sensing layer and the motion sensing layer constitute the electrode;

[0010] c) spraying a self-repairing adhesive layer on the surface of the electrode;

[0011] d) covering a PDMS film on the back surface of the flexible substrate to complete the packaging of the flexible substrate, and forming a wireless communication module by function integration.

[0012] Preferably, the electrode substrate material at least uses one of thermoplastic polyurethane and polydimethylsiloxane.

[0013] Preferably, the flexible substrate preparation process using thermoplastic polyurethane (TPU) as the substrate material is as follows:

[0014] Dissolve TPU particles in tetrahydrofuran, mix 0.5wt% graphene quantum dots, uniformly disperse by ultrasonic mixing, and prepare a 10wt% TPU particle solution; spin-coat the TPU particle solution on a glass substrate at a spin-coating speed of 1500 rpm for 60 s; freeze the glass substrate spin-coated with the TPU particle solution at a temperature of-20℃ for 12 hours, and then dry it in a vacuum for 2 hours at a drying temperature of 80℃; and obtain the flexible substrate after demolding after drying.

[0015] Preferably, the flexible substrate preparation process using polydimethylsiloxane (PDMS) as the substrate material is as follows:

[0016] Mix the PDMS prepolymer and the crosslinking agent at a mass ratio of 10:1, and introduce 0.5wt% graphene quantum dots; spin-coat the PDMS mixture on a glass substrate at a spin-coating speed of 1500 rpm for 60 s; freeze the glass substrate spin-coated with the mixture at a temperature of-20℃ for 12 hours;

[0017] Then placed in vacuum drying 2 hours, the drying temperature control at 80 degrees Celsius, the formation of PDMS film; cooling to room temperature, slowly stripping PDMS film after drying after demolding get flexible substrate.

[0018] Preferably, the preparation process of flexible substrate material made of thermoplastic polyurethane (TPU) and polydimethylsiloxane (PDMS) composite is as follows:

[0019] TPU particles are dissolved in DMF solvent, the mass ratio of TPU particles is 12wt%, then mixed with PDMS prepolymer with a mass ratio of 10:1, and graphene quantum dots are added and uniformly dispersed by ultrasonic mixing;

[0020] After mixing, spin coating on glass substrate, spin coating speed is 1500 rpm, time 60 s, then placed in-20℃ temperature for 12 hours, then placed in vacuum drying 2 hours, the drying temperature control at 80 degrees Celsius; after drying demolding get flexible substrate.

[0021] Preferably, the preparation process of the electrode is as follows:

[0022] TPU nanofiber web is deposited on the front surface of the substrate by electrospinning process, the fiber diameter is 200 nm, forming a porous structure; then, liquid metal with a particle size of 5 μm is sprayed on the porous structure, and the conductive path is activated by mechanical rolling, forming the electromyographic sensing layer;

[0023] Silver nanowires with a diameter of 30 nm and an aspect ratio of >1000 are mixed with TPU at a mass ratio of 1:5, screen printed on the front surface of the substrate, forming a serpentine microcrack structure; then it is heat cured, 60℃ annealing for 30 minutes, forming the motion sensing layer.

[0024] Preferably, a 3 μm thick ultra-thin polyurethane insulating layer is used to form a honeycomb micro-porous structure on the surface of the electromyographic sensing layer by laser lithography process, so as to isolate it from the motion sensing layer.

[0025] Preferably, dopamine, polyethylene glycol and dynamic hydrogen bond crosslinking agent are copolymerized, and 1wt% of silver-loaded mesoporous silica nanoparticles are doped to form a self-repairing adhesive colloid; the self-repairing adhesive colloid is sprayed on the electrode with a thickness of 30 μm; after spraying, the temperature is controlled at 60℃ for 10 minutes to form a porous and breathable structure with a pore size of 5-10 μm, thereby forming a self-repairing adhesive layer.

[0026] Preferably, a 50 μm thick PDMS film is covered on the back of the flexible substrate, and a 50 W power, 30 s time oxygen plasma treatment is used to realize seamless bonding with the back of the substrate, and the packaging is completed.

[0027] Preferably, the electrode contact is connected by a flexible circuit soldering machine with a serpentine copper wire with a line width of 50 μm, and a Bluetooth 5.0 chip and a micro lithium battery are integrated to form a wireless communication module.

[0028] The electromyographic signal and the motion signal of the electromyographic sensing layer and the motion sensing layer are respectively sampled by the wireless communication module at a frequency f;

[0029] The wireless communication module further comprises a signal amplifier and an analog-to-digital converter, which are respectively used to amplify the electromyographic signal and the motion signal and convert them into electromyographic digital signals and motion digital signals;

[0030] The format of the digital signal is: 16-bit data bit + 8-bit time stamp bit;

[0031] The root mean square value of the continuous electromyographic digital signal based on a fixed time window T is calculated to evaluate the muscle activation, and the median frequency is calculated to evaluate the muscle fatigue; and 30-bit electromyographic data is output, wherein the root mean square value is 12 bits, the median frequency is 10 bits, and the time stamp is 8 bits;

[0032] The temperature compensation value and the electrode deformation variable are calculated based on the continuous motion digital signal of the fixed time window T; and 26-bit motion data is output, wherein the electrode deformation variable is 10 bits, the temperature compensation value is 8 bits, and the time stamp is 8 bits;

[0033] The electromyographic digital signal, the motion digital signal, the electromyographic data, and the motion data are encapsulated into a data frame for transmission;

[0034] The data frame adopts the following self-defined format:

[0035] The frame header is 4 bytes, the data body is 24 bytes, and the check bit is 1 byte;

[0036] The frame header includes: electrode number 2 bytes, signal type 1 byte, and data body length 1 byte;

[0037] The signal type and the corresponding binary code are: electromyographic digital signal 0x01, motion digital signal 0x02, electromyographic data 0x03, and motion data 0x04;

[0038] The data body content is filled with different data according to different signal types;

[0039] The check bit is a CRC-8 check value, and the calculation range is the frame header and the data body;

[0040] The electromyographic data and the motion data are encapsulated into a data frame and transmitted to a computer terminal for analysis.

[0041] The preparation process has biocompatibility, the traditional conductive material is replaced by graphene quantum dot doped substrate, the risk of skin irritation is reduced, the biocompatibility is improved, the silver ion is continuously released by the silver-loaded mesoporous silica antibacterial adhesive layer, the growth of bacteria is effectively inhibited, the infection problem caused by long-term wearing is avoided, the self-repairing adhesive layer can quickly repair mechanical damage at low temperature, and the long-term stability and safety of the electrode are ensured.

[0042] The application has the characteristics of multi-modal signal anti-interference, the electromyography and the motion sensing layer are physically isolated by the honeycomb-shaped insulation isolation layer, the signal crosstalk is significantly reduced, the low impedance and high stability are provided by the liquid metal conductive path, and the reliability of signal transmission is ensured.

[0043] The application has good wearing comfort and long-term stability, the microporous structure is formed by the TPU / PDMS composite substrate through the freeze-drying process, the tensile property and fatigue resistance are improved, and the porous breathable adhesive layer

[0044] Good perspiration is provided, and the skin discomfort caused by long-term wearing is relieved. The wireless integrated module adopts a serpentine copper wire and a Bluetooth 5.0 chip, light weight design is realized, and the convenient needs of home rehabilitation scenes are met. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The overall flowchart provided by the application is provided.

[0046] Figure 2 The flexible substrate preparation flowchart provided by the application is provided.

[0047] Figure 3 The electrode preparation flowchart provided by the application is provided. DETAILED DESCRIPTION

[0048] The embodiments of the application are described below by specific examples, and those skilled in the art can easily understand other advantages and effects of the application from the disclosure. Obviously, the described embodiments are part of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the application.

[0049] The application provides a preparation process of a flexible stretchable surface electromyography motion sensing integrated electrode, and the specific steps are as follows:

[0050] The base material of the electrode can be thermoplastic polyurethane or polydimethylsiloxane PDMS.

[0051] Example 1: as shown in Figure 1 ​

[0052] a) Flexible substrate preparation:

[0053] The flexible substrate material uses thermoplastic polyurethane (TPU), with a thickness controlled at 50-200 μm.

[0054] Dissolve TPU particles in tetrahydrofuran, and mix 0.5wt% graphene quantum dots, uniformly mixed by ultrasonic dispersion, to prepare a 10wt% TPU particle solution; graphene quantum dots can improve the conductivity and fatigue resistance of the substrate.

[0055] Spin-coat the TPU particle solution on a glass substrate at a spin speed of 1500 rpm for 60 s; place the glass substrate with the spin-coated TPU particle solution in a freezer at -20°C for 12 hours, and then place it in a vacuum dryer for 2 hours, with the drying temperature controlled at 80°C; after drying and demolding, the flexible substrate is obtained, with a surface roughness <1 μm.

[0056] The power of ultrasonic dispersion is kept at 200 W for 30 minutes.

[0057] b) Bimodal sensing layer construction: including an electromyographic sensing layer and a motion sensing layer, as shown in Figure 3 .

[0058] Deposited on the front surface of the substrate by electrospinning process is a TPU nanofiber web with a fiber diameter of 200 nm, forming a porous structure; then, spray a liquid metal with a particle size of 5 μm on the porous structure, and mechanically roll to activate the conductive path, forming an electromyographic sensing layer;

[0059] An ultrathin polyurethane insulating layer with a thickness of 3 μm is used to form a honeycomb micro-porous structure on the surface of the electromyographic sensing layer by laser lithography process, forming an isolation layer to avoid signal crosstalk, and the experimental results are shown in Table 2.

[0060] Table 2 Experimental results of reducing signal crosstalk

[0061]

[0062] Mix silver nanowires with a diameter of 30 nm and an aspect ratio >1000 with TPU at a mass ratio of 1:5, screen print on the front surface of the substrate to form a serpentine micro-crack structure; then heat cure and anneal at 60°C for 30 minutes to form a motion sensing layer.

[0063] The electromyographic sensing layer and the motion sensing layer are vertically distributed on the substrate to form the electrode main body.

[0064] c) Self-repairing adhesive layer coating:

[0065] Dopamine, polyethylene glycol and dynamic hydrogen bond crosslinking agent are copolymerized, and 1wt% silver-loaded mesoporous silica nanoparticles are doped to form a self-repairing adhesive colloid; the self-repairing adhesive colloid is sprayed on the electrode with a thickness of 30μm; after spraying, the temperature is controlled at 60℃ for 10 minutes to form a porous and breathable structure with a pore size of 5-10μm. The self-repairing adhesive layer is formed through the above operation.

[0066] The slow-release silver ions in the silver-loaded mesoporous silica nanoparticles achieve long-acting antibacterial effect, solve the problem of skin infection caused by long-term wearing, and do not affect the self-repairing performance. The experimental results are shown in Table 1.

[0067] Table 1 Experimental results of inhibiting bacterial growth

[0068]

[0069] d) Packaging and function integration:

[0070] A PDMS film with a thickness of 50μm is covered on the back of the substrate, and seamless bonding with the back of the substrate is achieved through oxygen plasma treatment with a power of 50W and a time of 30s, and packaging is completed;

[0071] The serpentine copper wire with a line width of 50μm is connected to the electrode contact through a flexible circuit welding machine, and a Bluetooth 5.0 chip and a micro lithium battery are integrated to form a wireless communication module. The specific parameters are shown in Table 4.

[0072] Table 4 Main parameters and explanations of the wireless communication module

[0073]

[0074]

[0075] Example 2:

[0076] a) Preparation of flexible substrate

[0077] The flexible substrate material is PDMS, and the thickness is controlled to be 50-200μm,

[0078] The PDMS prepolymer is mixed with a crosslinking agent (such as Sylgard 184) at a mass ratio of 10:1, and 0.5wt% graphene quantum dots are introduced;

[0079] The PDMS mixed solution is spin-coated on a glass substrate at a spin speed of 1500rpm for 60s; the glass substrate with the mixed solution spin-coated is frozen at a temperature of-20℃ for 12 hours to form a microporous structure through phase separation, reduce internal stress and improve the flexibility of the substrate.

[0080] Then placed in vacuum drying 2 hours, the drying temperature control at 80 degrees Celsius, forming a PDMS film; cooling to room temperature, slowly peel off the PDMS film after drying after demolding get flexible substrate.

[0081] b) dual-mode sensing layer construction: including myoelectric sensing layer and motion sensing layer.

[0082] By electrospinning process in the deposition of TPU nanofiber web, the fiber diameter is 200 nm, forming a porous structure; then, on the porous structure, spray liquid metal with particle size of 5 μm, and mechanically roll to activate the conductive path, forming a myoelectric sensing layer;

[0083] The thickness of the 3 μm ultra-thin polyurethane insulating layer is used to form a honeycomb micro-porous structure on the surface of the myoelectric sensor layer by laser lithography process, forming an isolation layer to avoid signal crosstalk.

[0084] The silver nanowire with a diameter of 30 nm and an aspect ratio of > 1000 is mixed with TPU at a mass ratio of 1:5, screen printed on the front surface of the substrate, forming a serpentine micro-crack structure; then it is heat cured, 60 ℃ annealing for 30 minutes, forming a motion sensing layer.

[0085] The myoelectric sensing layer and the motion sensing layer are vertically distributed on the substrate to form the electrode main body.

[0086] c) self-repairing adhesive layer coating:

[0087] Copolymerization of dopamine, polyethylene glycol and dynamic hydrogen bond crosslinking agent, and doping 1wt% of silver-loaded mesoporous silica nanoparticles to form a self-repairing adhesive colloid; the self-repairing adhesive colloid is sprayed on the electrode with a thickness of 30 μm; after spraying, control the temperature to 60 ℃ for 10 minutes to form a porous and breathable structure with a pore size of 5-10 μm. The self-repairing adhesive layer is formed by the above operation.

[0088] The slow-release silver ions in the silver-loaded mesoporous silica nanoparticles achieve long-acting antibacterial effect, solving the problem of skin infection caused by long-term wearing without affecting the self-repairing performance.

[0089] d) packaging and function integration:

[0090] A PDMS film with a thickness of 50 μm is covered on the back of the substrate, and a power of 50 W and a time of 30 s of oxygen plasma treatment is used to realize seamless bonding with the back of the substrate, completing the packaging;

[0091] The serpentine copper wire with a line width of 50 μm is connected to the electrode contact by a flexible circuit welding machine, and a Bluetooth 5.0 chip and a micro lithium battery are integrated to form a wireless communication module.

[0092] Example 3:

[0093] a) flexible substrate preparation, such asFigure 2 as shown:

[0094] The TPU / PDMS composite substrate has a thickness of 50-200 μm.

[0095] The TPU particles are dissolved in DMF solvent (12 wt%) and mixed with the PDMS prepolymer (10:1 mass ratio), and the graphene quantum dots are uniformly dispersed by ultrasonic mixing after adding the graphene quantum dots.

[0096] After mixing, spin coating is performed on a glass substrate at a spin speed of 1500 rpm for 60 s, and then the substrate is frozen at a temperature of -20°C for 12 hours, and then dried in a vacuum for 2 hours at a drying temperature of 80°C. After demolding, the flexible substrate is obtained, and the tensile property and fatigue resistance test results are shown in Table 3.

[0097] Table 3 Tensile property and fatigue resistance test results

[0098]

[0099]

[0100] The power of the ultrasonic dispersion is kept at 200 W for 30 minutes.

[0101] b) Bimodal sensing layer construction: including an electromyographic sensing layer and a motion sensing layer.

[0102] A TPU nanofiber web is deposited on the front surface of the substrate by an electrospinning process, with a fiber diameter of 200 nm and a porous structure formed. Then, a liquid metal with a particle size of 5 μm is sprayed on the porous structure, and a conductive path is activated by mechanical rolling to form an electromyographic sensing layer.

[0103] An ultrathin polyurethane insulating layer with a thickness of 3 μm is used, and a honeycomb micro-porous structure is formed on the surface of the electromyographic sensor layer by a laser lithography process to form an isolation layer, avoiding signal crosstalk.

[0104] Silver nanowires with a diameter of 30 nm and an aspect ratio >1000 are mixed with TPU at a mass ratio of 1:5, and screen printed on the front surface of the substrate to form a serpentine micro-crack structure. Then, it is heat cured and annealed at 60°C for 30 minutes to form a motion sensing layer.

[0105] The electromyographic sensing layer and the motion sensing layer are vertically distributed on the substrate to form an electrode main body.

[0106] c) Self-repairing adhesive layer coating:

[0107] Dopamine, polyethylene glycol and dynamic hydrogen bond crosslinking agent are copolymerized, and 1wt% of silver-loaded mesoporous silica nanoparticles are doped to form a self-repairing adhesive colloid; the self-repairing adhesive colloid is sprayed on the electrode with a thickness of 30μm; after spraying, the temperature is controlled at 60℃ for 10 minutes to form a porous and breathable structure with a pore size of 5-10μm. The self-repairing adhesive layer is formed through the above operation.

[0108] The long-acting antibacterial effect is achieved by the slow-release silver ions in the silver-loaded mesoporous silica nanoparticles, solving the problem of skin infection caused by long-term wearing without affecting the self-repairing performance.

[0109] d) encapsulation and functional integration:

[0110] A PDMS film with a thickness of 50μm is covered on the back of the substrate, and a seamless bond with the back of the substrate is achieved through oxygen plasma treatment with a power of 50W and a time of 30s, completing encapsulation;

[0111] The serpentine copper wire with a line width of 50μm is connected to the electrode contact through a flexible circuit welding machine, and a Bluetooth 5.0 chip and a micro lithium battery are integrated to form a wireless communication module.

[0112] Control group 1:

[0113] The difference from Example 1 is that 1wt% of silver-loaded mesoporous silica nanoparticles is not added.

[0114] Control group 2:

[0115] The difference from Example 1 is that a homogeneous polyurethane coating with a thickness of 3μm is used without micropores.

[0116] Example 4: This example gives the detailed workflow of the wireless communication module

[0117] The myoelectric signal and the motion signal of the myoelectric sensing layer and the motion sensing layer are respectively sampled by the wireless communication module at a frequency of 1024Hz;

[0118] The wireless communication module also has a signal amplifier and an analog-to-digital converter built-in, respectively used to amplify the myoelectric signal and the motion signal and convert them into myoelectric digital signal and motion digital signal;

[0119] Myoelectric digital signal format: (16-bit data + 8-bit timestamp, sampling rate 1024Hz, amplitude range 50μV-5mV).

[0120] Based on the continuous myoelectric digital signal with a fixed time window of 200ms, the root mean square value is calculated to evaluate the muscle activation, and the median frequency is calculated to evaluate the muscle fatigue; and 30-bit myoelectric data is outputted (root mean square value 12 bits + median frequency 10 bits + timestamp 8 bits).

[0121] The root mean square (RMS) value is calculated as follows:

[0122] The time window length is 200 ms (205 sampling points, 205 = 1024 x 0.2).

[0123] The calculation formula is as follows: Where x i is the sampling value in the window.

[0124] The output precision is 12-bit fixed point (Q10.2 format, range 0-1023.75).

[0125] The calculation of the median frequency is relatively simple, and this embodiment will not be described;

[0126] The temperature compensation value and the electrode deformation variable are calculated based on the continuous motion digital signal of the fixed time window T, and 26-bit motion data (10-bit electrode deformation variable + 8-bit temperature compensation value + 8-bit timestamp) is output; the temperature compensation value is collected by the temperature sensor built in the wireless communication module;

[0127] The motion digital signal format (16-bit data + 8-bit timestamp, sampling rate 1024 Hz, data is the resistance change rate ΔR / R0).

[0128] The temperature compensation value calculation formula is as follows: Where: a is the temperature coefficient of silver nanowires; β is the strain coefficient, which is determined by calibration experiments; γ is the nonlinear temperature coefficient; and the temperature ΔT is provided by the integrated micro temperature sensor (such as TMP117).

[0129] The calculation formula of the deformation variable is as follows: Where ΔR0 / R0 is the initial resistance change rate, i.e. when there is no deformation.

[0130] The output precision is 10-bit fixed point (range 0-1023, corresponding to 0-100%).

[0131] In this embodiment, the electromyographic digital signal, the motion digital signal, the electromyographic data, and the motion data are packaged into a data frame for transmission;

[0132] The data frame adopts the following self-defined format:

[0133] The frame header is 4 bytes;

[0134] The device ID is 2 bytes, which can be a fixed value 0x5A5A (identified as a flexible dual-mode electrode). The signal type (1 byte) includes: 0x01 = electromyographic digital signal; 0x02 = motion digital signal; 0x03 = electromyographic data; 0x04 = motion data;

[0135] The data length (1 byte) indicates the length of the subsequent data body (range 1-24 bytes).

[0136] Data body (24 bytes), different data according to signal type, in this embodiment as follows:

[0137] Myoelectricity digital signal, 12 sampling points (each 16 bits, total 24 bytes).

[0138] Motion digital signal, 12 sampling points (each 16 bits, total 24 bytes)

[0139] Myoelectricity data, 12 bits of root mean square value + 10 bits of median frequency + 2 bits of state flag, repeated 3 times (covering 600 ms data), and then filled to 24 bytes.

[0140] Motion data: 10 bits of electrode deformation value + 8 bits of temperature compensation value, total 18 bits, compressed to 3 bytes every 2 frames, and then filled to 24 bytes.

[0141] Check bit is CRC-8 check value, calculation range is frame header and data body, its polynomial is x 8 +x 2 +x+1 (0x07).

[0142] Although the present application has been described in detail with general description and specific embodiments above, some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application, all belong to the scope of the present application claimed.

Claims

1. A fabrication process for a flexible, stretchable surface electromyography sensor integrated electrode, characterized in that: The preparation steps include the following: a) Flexible substrate preparation: The electrode substrate material is prepared into a solution and then spin-coated onto a glass substrate. The glass substrate with the solution spin-coated is then frozen and dried. After drying, it is demolded to obtain the flexible substrate. b) Electrode fabrication: A dual-modal sensing layer consisting of an electromyography (EMG) sensing layer and a motion sensing layer is distributed on the front side of the flexible substrate obtained in step a). The EMG sensing layer is prepared by depositing a TPU fiber mesh on the flexible substrate, spraying liquid metal, and activating conductive pathways in sequence. The motion sensing layer is prepared by screen printing a mixture of silver nanowires and TPU onto the substrate surface and then using a thermosetting technique. The flexible substrate, electromyography sensing layer, and motion sensing layer constitute the electrode. c) Spray a self-healing adhesive layer onto the electrode surface; d) Cover the back of the flexible substrate with a PDMS film to complete the flexible substrate encapsulation, and form a wireless communication module through functional integration.

2. The fabrication process of the flexible, stretchable surface electromyography sensor integrated electrode according to claim 1, characterized in that: The electrode substrate material shall be at least one of thermoplastic polyurethane or polydimethylsiloxane.

3. The fabrication process of the flexible, stretchable surface electromyography sensor integrated electrode according to claim 2, characterized in that: The process for preparing a flexible substrate using thermoplastic polyurethane (TPU) as the base material is as follows: TPU particles were dissolved in tetrahydrofuran and mixed with 0.5 wt% graphene quantum dots. The mixture was then ultrasonically dispersed and mixed to prepare a 10 wt% TPU particle solution. The TPU particle solution was spin-coated onto a glass substrate at a spin speed of 1500 rpm for 60 s. The glass substrate with the spin-coated TPU particle solution was frozen at -20°C for 12 hours and then vacuum dried at 80°C for 2 hours. After drying, the substrate was demolded to obtain a flexible substrate.

4. The fabrication process of the flexible, stretchable surface electromyography sensor integrated electrode according to claim 2, characterized in that: The process for preparing a flexible substrate using polydimethylsiloxane (PDMS) as the substrate material is as follows: PDMS prepolymer and crosslinking agent were mixed at a mass ratio of 10:1, and 0.5 wt% graphene quantum dots were introduced; the PDMS mixture was spin-coated onto a glass substrate at a spin speed of 1500 rpm for 60 s; the glass substrate with the spin-coated mixture was placed at -20℃ and frozen for 12 hours. Then, it is placed in a vacuum for 2 hours, with the drying temperature controlled at 80 degrees Celsius, to form a PDMS film. After cooling to room temperature, the PDMS film is slowly peeled off, dried, and demolded to obtain a flexible substrate.

5. The fabrication process of the flexible, stretchable surface electromyography sensor integrated electrode according to claim 2, characterized in that: The preparation process of flexible substrate material using thermoplastic polyurethane (TPU) and polydimethylsiloxane (PDMS) composite material is as follows: TPU particles were dissolved in DMF solvent at a mass ratio of 12 wt%, and then mixed with PDMS prepolymer at a mass ratio of 10:

1. After adding graphene quantum dots, the mixture was ultrasonically dispersed and mixed evenly. After mixing, the mixture is spin-coated onto a glass substrate at a speed of 1500 rpm for 60 seconds. Then, it is frozen at -20°C for 12 hours and then vacuum dried at 80°C for 2 hours. After drying, the flexible substrate is obtained after demolding.

6. The fabrication process of the flexible, stretchable surface electromyography sensor integrated electrode according to claim 1, characterized in that: The electrode is prepared as follows: TPU nanofiber mesh with a fiber diameter of 200 nm was deposited on the front side of the substrate by electrospinning to form a porous structure. Then, liquid metal with a particle size of 5 μm was sprayed on the porous structure and mechanically rolled to activate the conductive pathways to form an electromyographic sensing layer. Silver nanowires with a diameter of 30 nm and an aspect ratio of >1000 were mixed with TPU at a mass ratio of 1:5 and screen-printed onto the front side of the substrate to form a serpentine microcrack structure; then it was thermo-cured and annealed at 60°C for 30 minutes to form a motion sensing layer.

7. The fabrication process of the flexible, stretchable surface electromyography sensor integrated electrode according to claim 6, characterized in that: A 3μm thick ultrathin polyurethane insulating layer is used, and a honeycomb microporous structure is formed on the surface of the electromyography sensing layer through laser photolithography to isolate it from the motion sensing layer.

8. The fabrication process of the flexible, stretchable surface electromyography sensor integrated electrode according to claim 1, characterized in that: Dopamine, polyethylene glycol, and a dynamic hydrogen bonding crosslinking agent were copolymerized and doped with 1 wt% silver-loaded mesoporous silica nanoparticles to form a self-healing adhesive colloid. The self-healing adhesive colloid was sprayed onto the electrode to a thickness of 30 μm. After spraying, the electrode was cured at 60℃ for 10 minutes to form a porous and breathable structure with a pore size of 5–10 μm, thus forming a self-healing adhesive layer.

9. The fabrication process of the flexible, stretchable surface electromyography sensor integrated electrode according to claim 1, characterized in that: A 50μm thick PDMS film is coated on the back of a flexible substrate, and seamless bonding with the back of the substrate is achieved through oxygen plasma treatment with a power of 50W for 30s, thus completing the encapsulation.

10. The fabrication process of the flexible, stretchable surface electromyography sensor integrated electrode according to claim 1, characterized in that: A flexible circuit welding machine is used to connect 50μm wide serpentine copper wires to electrode contacts, and a Bluetooth 5.0 chip and a micro lithium battery are integrated to form a wireless communication module. The electromyographic and motion signals of the electromyographic sensing layer and the motion sensing layer are sampled at a frequency f using a wireless communication module. The wireless communication module also has a built-in signal amplifier and analog-to-digital converter, which are used to amplify and convert electromyographic signals and motion signals into electromyographic digital signals and motion digital signals, respectively. The format of a digital signal is: 16 data bits + 8 timestamp bits; The root mean square (RMS) value is calculated based on continuous digital electromyography (EMG) signals within a fixed time window T to assess muscle activation, and the median frequency is calculated to assess muscle fatigue. The output is 30-bit EMG data, including 12 bits for the RMS value, 10 bits for the median frequency, and 8 bits for the timestamp. Calculate temperature compensation value and electrode deformation based on continuous motion digital signal with a fixed time window T; and output 26 bits of motion data, including 10 bits of electrode deformation, 8 bits of temperature compensation value and 8 bits of timestamp; Electromyographic digital signals, motion digital signals, electromyographic data, and motion data are encapsulated into data frames for transmission; The data frame uses the following custom format: Frame header 4 bytes; data body 24 bytes; checksum 1 byte; The frame header includes: electrode number (2 bytes), signal type (1 byte), and data body length (1 byte); The signal types and their corresponding binary codes are: electromyographic digital signal 0x01, motion digital signal 0x02, electromyographic data 0x03, and motion data 0x04; The data body content is filled with different data according to different signal types; The check bit is a CRC-8 check value, and the calculation range includes the frame header and the data body. The electromyographic and motion data are encapsulated into data frames and transmitted to a computer terminal for analysis.

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