Breathable conductive hydrogel electrode and preparation method and application thereof

Abstract

This invention discloses a breathable, conductive hydrogel electrode, its preparation method, and its applications. The breathable, conductive hydrogel electrode comprises a porous fiber support structure and a hydrogel conductive network. The porous fiber support structure has a three-dimensional porous structure formed by interwoven porous fibers, each fiber possessing a three-dimensional interconnected channel structure formed by interconnected pores distributed on and within the porous fibers. The hydrogel conductive network is distributed on the surface and within the porous fiber support structure, forming a continuous ion conduction path within the electrode. The breathable, conductive hydrogel electrode provided by this invention has advantages such as high breathability, self-humidification, low impedance, and breathability, achieving high-fidelity, long-term acquisition of physiological signals such as electroencephalograms (EEG), electrocardiograms (ECG), and electromyograms (EMG). It can be widely used in electrophysiological signal monitoring, smart wearables, sleep analysis, and human-computer interaction.

Description

Technical Field

[0001] This invention belongs to the field of flexible electrode technology, specifically relating to a breathable, conductive hydrogel electrode, its preparation method, and its application. Background Technology

[0002] Wearable electrophysiological monitoring technology collects bioelectrical signals such as electroencephalograms (EEG), electrocardiograms (ECG), and electromyograms (EMG) on the skin surface to achieve real-time monitoring of physiological indicators such as nervous system activity, cardiovascular health, and fatigue status. It holds significant application prospects in fields such as smart healthcare, neuroscience research, and human-computer interaction. Compared to traditional medical testing, this technology overcomes the limitations of time and space, enabling continuous, non-invasive tracking of an individual's physiological dynamics and early identification of potential health risks. In high-load scenarios such as prolonged driving, work, or study, EEG signals, as indicators directly reflecting central nervous system activity, can provide early warnings of fatigue accumulation before behavioral changes occur, thus holding crucial value in intelligent transportation and driving safety. However, achieving high-quality, long-term, and stable electrophysiological signal acquisition still faces dual challenges in materials and interface engineering.

[0003] Currently widely used flexible electrodes are typically constructed from conductive polymers, metal films, or composite materials, using polymers such as polyimide (PI), polyethylene terephthalate (PET), and polydimethylsiloxane (PDMS) as a substrate. While these electrodes possess a degree of flexibility and processability, their Young's modulus is usually in the MPa to GPa range, resulting in a significant mechanical mismatch with human skin (tens of kPa), making stable adhesion difficult. Tiny air gaps between the electrode and skin lead to increased contact impedance and exacerbated signal distortion, while limited permeability easily causes sweat accumulation and skin discomfort, resulting in signal drift and long-term monitoring failure. These problems limit the performance of traditional flexible electrodes in high-sensitivity, long-term electrophysiological monitoring.

[0004] To improve the compliance and signal stability of the electrode-skin interface, ion-conducting hydrogel electrodes have received widespread attention in recent years. Due to their high water content, ion conductivity, and excellent biocompatibility, hydrogels can form a low-impedance ion-to-ion conduction interface with the skin in a humid environment, thereby significantly improving signal fidelity. Compared with electronically conductive electrodes, hydrogels are more compatible with the physiological environment of skin tissue, reducing electrochemical noise and improving wearing comfort.

[0005] However, the inherent aqueous ionic properties of hydrogel systems also present multiple challenges: First, most traditional hydrogels, such as polyacrylamide hydrogel (PAM), polyvinyl alcohol hydrogel (PVA), and poly(hydroxyethyl methacrylate) hydrogel (PHEMA), have dense and impermeable structures. When applied to the skin, they form a closed interface, hindering sweat evaporation and gas exchange, leading to changes in ion concentration and signal drift. Second, hydrogels are prone to dehydration in the environment. Decreased water content weakens conductivity and increases impedance, affecting signal stability. Third, to delay dehydration, high-concentration glycerol (>50 wt%) formulations are commonly used. However, high-glycerol systems not only have high viscosity and a sticky texture but also dilute migrating ions and increase migration resistance, thereby weakening conductivity and causing discomfort. Furthermore, hydrated hydrogels are prone to shear slippage between themselves and the skin during movement, further leading to unstable contact and noise interference. These problems collectively limit the reliable application of hydrogel electrodes in long-term, highly dynamic environments.

[0006] Therefore, achieving high breathability, mechanical flexibility, and stable ionic conductivity simultaneously in flexible electrode systems has long presented a significant structural contradiction. On the one hand, improving electrode breathability typically relies on introducing porous or loose structures, but excessive porosity can easily disrupt the continuity of the ion conduction network, leading to increased interfacial impedance and decreased signal stability. On the other hand, to ensure stable ionic conductivity and adhesion, dense or highly hydrated hydrogel structures are often used. These structures tend to form localized closed interfaces after being applied to the skin, hindering sweat evaporation and gas exchange, thereby causing moisture accumulation, fluctuations in ion concentration, and discomfort.

[0007] Furthermore, human skin is in a state of continuous movement and dynamic sweating during actual wear. The electrode-skin interface not only endures periodic stretching and shearing, but also experiences fluctuations in local humidity and temperature. Traditional flexible electrodes often employ layered or simple composite structures, making it difficult to simultaneously coordinate mechanical deformation, ion conduction, and water vapor exchange processes at the microscopic scale. This can easily lead to problems such as interface slippage, signal drift, and decreased comfort under long-term wear or complex movement conditions.

[0008] Therefore, how to construct a structural system inside the electrode that can maintain the continuity of ion conduction while allowing water vapor exchange and deformation coordination, based on the interface structure and microenvironment regulation mechanism, in order to achieve a dynamic balance between conductivity, breathability and wearing comfort at the electrode-skin interface, has become a key scientific and engineering problem that urgently needs to be solved in the field of wearable electrophysiological monitoring and intelligent human-computer interaction. Summary of the Invention

[0009] The main objective of this invention is to provide a breathable, conductive hydrogel electrode, its preparation method, and its application, in order to overcome the shortcomings of the prior art.

[0010] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0011] The first aspect of the present invention provides a breathable and conductive hydrogel electrode, which includes a porous fiber support structure having a three-dimensional porous structure formed by interwoven porous fibers, wherein the porous fibers have a three-dimensional through-pore structure, and the three-dimensional through-pore structure is formed by interconnected pores distributed on the surface and inside of the porous fibers.

[0012] A hydrogel conductive network is distributed on the surface and inside of the porous fiber support structure to form a continuous ion conduction path inside the electrode.

[0013] The hydrogel conductive network is also partially embedded in a local area of ​​the three-dimensional through-hole structure, thereby forming an interlaced and continuously coupled embedded reinforcement structure at the microscale, and retaining gas transmission channels within the three-dimensional through-hole structure.

[0014] A second aspect of the present invention provides a method for preparing the breathable, conductive hydrogel electrode, comprising:

[0015] An organic fiber network is provided, which has a three-dimensional porous structure formed by interwoven organic fibers;

[0016] The organic fiber network is subjected to hydrophilic treatment to transform the organic fibers into porous fibers, and hydrophilic groups are introduced at least on the surface of the porous fibers to obtain a porous fiber support structure.

[0017] A hydrogel precursor solution is applied to the porous fiber support structure, and a portion of the hydrogel precursor solution enters the interior of the porous fiber support structure. Then, a freeze-thaw cycle is performed to obtain a freeze-thaw molded body.

[0018] The electrode is obtained by immersing the freeze-thawed body in a post-treatment solution and then removing it, wherein the post-treatment solution contains a humectant and at least one of the hydrogel precursor solution and the post-treatment solution contains an electrolyte.

[0019] A third aspect of the invention provides the application of the breathable, conductive hydrogel electrode in electrophysiological signal monitoring, sleep analysis, or human-computer interaction.

[0020] A fourth aspect of the present invention provides a wearable device comprising the aforementioned breathable, conductive hydrogel electrode.

[0021] A fifth aspect of the present invention provides an electrophysiological signal monitoring system comprising the aforementioned breathable conductive hydrogel electrode.

[0022] A sixth aspect of the present invention provides a method for monitoring electrophysiological signals, comprising:

[0023] Provide the breathable, conductive hydrogel electrode;

[0024] The breathable and conductive hydrogel electrode is attached to the skin surface of the subject, and the electrode array therein is in contact with the subject's skin to collect the subject's electrophysiological signals, which include one or more of electroencephalogram (EEG), electrocardiogram (ECG), and electromyogram (EMG).

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) The breathable and conductive hydrogel electrode provided by the present invention constructs an embedded reinforcement structure of a three-dimensional porous skeleton and hydrogel network on the micro-nano scale, forming a composite system with synergistic mechanical and ion conduction properties, and can form a symbiotic interface that can be dynamically balanced with the skin. It has the advantages of high breathability, self-humidification, low impedance and breathability, and realizes high-fidelity and long-term acquisition of physiological signals such as electroencephalogram, electrocardiogram and electromyogram.

[0027] (2) The breathable and conductive hydrogel electrode provided by the present invention has a three-dimensional through-hole structure. The three-dimensional through-hole structure is partially retained after the formation of the embedded reinforcement structure, which is used to provide gas and water vapor diffusion paths and limit the spatial distribution of the hydrogel conductive network.

[0028] (3) The breathable and conductive hydrogel electrode provided by the present invention has an embedded reinforcement structure, which can form a micro-mechanical locking structure composed of fiber skeleton and hydrogel conductive network at the skin contact interface to suppress interface slippage caused by relative displacement during wearing.

[0029] (4) The breathable and conductive hydrogel electrode provided by the present invention can maintain stable conductivity and signal output quality in high humidity environment or long-term wear conditions, and is suitable for fatigue monitoring, smart wearable, sleep analysis and human-computer interaction scenarios. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the fabrication process of a breathable and conductive hydrogel electrode in a typical embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram illustrating the application scenario of the breathable and conductive hydrogel electrode in a typical embodiment of the present invention.

[0033] Figure 3 This is a scanning electron microscope image of the breathable, conductive hydrogel electrode of Embodiment 1 of the present invention at 5 micrometers.

[0034] Figure 4 This is a scanning electron microscope image of the breathable, conductive hydrogel electrode of Embodiment 1 of the present invention at 2 micrometers.

[0035] Figure 5 This is a porosity test diagram of the breathable and conductive hydrogel electrode of Embodiment 1 of the present invention.

[0036] Figure 6 This is a breathability test diagram of the breathable, conductive hydrogel electrode of Embodiment 1 of the present invention.

[0037] Figure 7 This is a mechanical test diagram of the breathable and conductive hydrogel electrode of Embodiment 1 of the present invention.

[0038] Figure 8 This is a bending ability test diagram of the breathable and conductive hydrogel electrode of Embodiment 1 of the present invention.

[0039] Figure 9 The impedance test diagram of the breathable and conductive hydrogel electrode of Embodiment 1 of the present invention is shown.

[0040] Figure 10 An optical image of the breathable, conductive hydrogel electrode of Embodiment 1 of the present invention;

[0041] Figure 11 This is a time-current density graph showing the charge injection capability test of the breathable and conductive hydrogel electrode of Embodiment 1 of the present invention.

[0042] Figure 12 The graph shows the charge injection capability test of the breathable conductive hydrogel electrode of Embodiment 1 of the present invention under 1, 10, 100, and 1000 cycles.

[0043] Figure 13 This is a data graph showing the charge injection capacity of the breathable and conductive hydrogel electrode of Embodiment 1 of the present invention.

[0044] Figure 14 This is a test graph showing the voltage tracking capability of the breathable and conductive hydrogel electrode in Embodiment 1 of the present invention at 0.1 Hz.

[0045] Figure 15 This is a test graph showing the voltage tracking capability of the breathable and conductive hydrogel electrode in Embodiment 1 of the present invention at 1 Hz.

[0046] Figure 16 This is a test graph showing the voltage tracking capability of the breathable and conductive hydrogel electrode in Embodiment 1 of the present invention at 1 kHz.

[0047] Figure 17 This is a test graph showing the voltage tracking capability of the breathable and conductive hydrogel electrode in Embodiment 1 of the present invention at 100kHz.

[0048] Figure 18 This is a biocompatibility test diagram of the breathable and conductive hydrogel electrode of Embodiment 1 of the present invention.

[0049] Figure 19 This is a diagram of in vivo muscle electrophysiological signals collected by the breathable, conductive hydrogel electrode of Embodiment 1 of the present invention.

[0050] Figure 20 This is an in vivo electrocardiogram image of the breathable, conductive hydrogel electrode of Embodiment 1 of the present invention.

[0051] Figure 21 This is an in vivo electroencephalogram (EEG) image of the breathable, conductive hydrogel electrode of Embodiment 1 of the present invention.

[0052] Figure 22 The image shows the waveforms of alpha, beta, gamma, theta, and delta separated from the electroencephalogram (EEG) signals collected in vivo by the breathable and conductive hydrogel electrode of Embodiment 1 of the present invention. Detailed Implementation

[0053] In view of the problems existing in the prior art, after extensive and in-depth research, a breathable and conductive hydrogel electrode, its preparation method and application are provided.

[0054] The following will provide a further explanation of the technical solution, its implementation process, and its principles.

[0055] The first aspect of the present invention provides a breathable and conductive hydrogel electrode, which includes a porous fiber support structure having a three-dimensional porous structure formed by interwoven porous fibers, wherein the porous fibers have a three-dimensional through-pore structure, and the three-dimensional through-pore structure is formed by interconnected pores distributed on the surface and inside of the porous fibers.

[0056] A hydrogel conductive network is distributed on the surface and inside of the porous fiber support structure to form a continuous ion conduction path inside the electrode.

[0057] The hydrogel conductive network is also partially embedded in a local area of ​​the three-dimensional through-hole structure, thereby forming an interlaced and continuously coupled embedded reinforcement structure at the microscale, and retaining gas transmission channels within the three-dimensional through-hole structure.

[0058] In some embodiments, the diameter of the porous fiber is 1~3μm.

[0059] In some embodiments, the porosity of the porous fiber is 50% or more.

[0060] Furthermore, the porosity of the porous fiber is 70-80%.

[0061] In some embodiments, the porous fiber is made of at least one of polylactic acid, polyurethane, polyhexamethylene adipamide, etc., but is not limited thereto.

[0062] In some embodiments, the pores in the three-dimensional through-hole structure have a diameter of 100~400nm and a porosity of 35~56%.

[0063] In some embodiments, the porosity of the porous fiber support structure is 30% or more.

[0064] Furthermore, the porosity of the porous fiber support structure is 40-50%.

[0065] In some embodiments, the pores in the porous fiber support structure have a diameter of 1~3μm.

[0066] In some embodiments, the hydrogel conductive network comprises a polymer hydrogel network and electrolytes and humectants uniformly distributed within the polymer hydrogel network.

[0067] In some embodiments, the thickness of the breathable conductive hydrogel electrode is 10~125 μm.

[0068] Furthermore, the network skeleton material of the polymer hydrogel network includes at least one of polyvinyl alcohol, polyacrylamide, polyacrylic acid, alginate, gelatin, chitosan, etc., but is not limited to this.

[0069] Furthermore, the electrolyte includes, but is not limited to, at least one of NaCl, KCl, CaCl2, MgCl2, LiCl, phosphate buffer solution (PBS), etc.

[0070] Furthermore, the moisturizer includes, but is not limited to, at least one of glycerin, propylene glycol, butylene glycol, polyethylene glycol, betaine, etc.

[0071] Furthermore, the hydrogel conductive network comprises 86.7~94.1 wt% polymer hydrogel network, 0.9~3.6 wt% electrolyte and 5~10 wt% humectant.

[0072] Furthermore, the mass ratio of the porous fiber support structure to the hydrogel conductive network is 2~4:6~8.

[0073] Furthermore, the thickness of the porous fiber support structure is 10~80μm.

[0074] Furthermore, the thickness of the hydrogel covering the surface of the porous fiber support structure is 5~20μm.

[0075] Furthermore, the breathable conductive hydrogel electrode has an impedance of 10~100Ω at 1 kHz, a contact impedance of 0.2~5 kΩ, and a water vapor permeability of 0.9~2.2 kg·m. - ²·day - ¹, the moisture loss rate within 14 days is no more than 15%.

[0076] Furthermore, the breathable and conductive hydrogel electrode has a signal-to-noise ratio >19dB in electrophysiological signal monitoring.

[0077] A second aspect of the present invention provides a method for preparing the breathable, conductive hydrogel electrode, comprising:

[0078] An organic fiber network is provided, which has a three-dimensional porous structure formed by interwoven organic fibers;

[0079] The organic fiber network is subjected to hydrophilic treatment to transform the organic fibers into porous fibers, and hydrophilic groups are introduced at least on the surface of the porous fibers to obtain a porous fiber support structure.

[0080] A hydrogel precursor solution is applied to the porous fiber support structure, and a portion of the hydrogel precursor solution enters the interior of the porous fiber support structure. Then, a freeze-thaw cycle is performed to obtain a freeze-thaw molded body.

[0081] The electrode is obtained by immersing the freeze-thawed body in a post-treatment solution and then removing it, wherein the post-treatment solution contains a humectant and at least one of the hydrogel precursor solution and the post-treatment solution contains an electrolyte.

[0082] In some embodiments, the organic fiber network is prepared by at least electrospinning.

[0083] Furthermore, the electrospinning specifically includes: providing an electrospinning solution with a concentration of 9~10 wt%, setting a voltage of 9~15 kV, a injection rate of 1~2 mm / min, an ambient temperature of 20~26 ℃, a relative humidity of 70~80%, a collection time of 0.5~8 min, and a distance of 5~15 cm between the nozzle and the collection plate.

[0084] Furthermore, the electrospinning solution comprises 9-10 wt% polylactic acid and 90-91 wt% organic solvent. The organic solvent comprises a combination of dichloromethane and N,N-dimethylformamide, wherein the mass ratio of dichloromethane to N,N-dimethylformamide is 88-92:8-12. The polylactic acid has a molecular weight of 50,000 to 300,000.

[0085] In some embodiments, oxygen plasma is used to perform the hydrophilic treatment on the organic fiber network.

[0086] Furthermore, the power of the oxygen plasma is set to 50~100W, and the oxygen plasma is made to come into intermittent contact with the organic fiber network 2~5 times, with each contact lasting 1~2 minutes and the interval time being 1~3 minutes.

[0087] In some embodiments, the hydrogel precursor solution is applied to the porous fiber support structure by at least dip coating and / or spin coating.

[0088] Furthermore, the hydrogel precursor solution is first dip-coated and then spin-coated onto the surface of the porous fiber support structure, with the spin-coating speed controlled at 500~5000 rpm and the time at 10~30 s, repeated 1~3 times, and then subjected to the freeze-thaw cycle treatment.

[0089] Furthermore, the method for preparing the hydrogel precursor solution includes: stirring a mixed solution containing the polyvinyl alcohol and the electrolyte at a stirring speed of 300-500 rpm at 80-95 °C for 4-8 h to obtain the hydrogel precursor solution.

[0090] In some embodiments, the freeze-thaw cycle includes freezing at -30 to -20 °C for 30 to 60 min, then thawing at room temperature for 3 to 10 min, and repeating the freeze-thaw cycle 1 to 6 times.

[0091] In some embodiments, the preparation method includes immersing the freeze-thawed body in a post-processing solution for 0.5 to 5 minutes.

[0092] In some embodiments, the preparation method further includes: patterning or arraying the post-processed freeze-thawed body to form a target electrode.

[0093] Furthermore, the shape of the target electrode includes any one of the following: circular structure, strip structure, and array structure, but is not limited to these.

[0094] In some embodiments, the hydrogel precursor solution contains 1-7 wt% polyvinyl alcohol and 0.9-3.6 wt% sodium chloride.

[0095] In some embodiments, the post-treatment solution contains 10-50 wt% glycerol and 0.9-3.6 wt% sodium chloride.

[0096] In some embodiments, the preparation method may further include: depositing a conductive layer on the surface of the breathable conductive hydrogel electrode by at least screen printing or electron beam evaporation.

[0097] In some more specific embodiments, the preparation method of the breathable and conductive hydrogel electrode specifically includes the following steps:

[0098] S1. Using polylactic acid (PLA) with a molecular weight of 50,000 to 300,000 as the supporting material, PLA is dissolved in a mixed solvent of dichloromethane (DCM) and N,N-dimethylformamide (DMF) at a ratio of 88-92:8-12. The mixture is stirred for 2-6 hours to obtain a homogeneous polylactic acid solution with a mass fraction of 10 wt%.

[0099] S2. The homogeneous polylactic acid solution from step S1 is loaded into a syringe and spun using an electrospinning device at a voltage of 12 kV and a distance of 5–15 cm between the nozzle and the collecting plate. The injection rate is 1–2 mm / min. The ambient temperature is 20–26°C and the relative humidity is 70–80%. The collection time is 0.5–30 minutes, resulting in a porous fiber membrane (PLA membrane) with a thickness of approximately 10–80 μm, wherein the average fiber diameter is approximately 1–3 μm and the porosity is approximately 35–65%. The resulting membrane forms three-dimensional interconnected channels, providing support for subsequent hydrogel infiltration.

[0100] S3. To improve the hydrophilicity of the PLA membrane obtained in step S2, oxygen plasma treatment is performed. The oxygen plasma power is 50~100W, the treatment time is 60~90s, and the treatment is repeated 2~5 times. This step can introduce –OH and –COOH groups onto the surface of the porous fibers, thereby improving the adhesion of the subsequent hydrogel layer.

[0101] S4. Polyvinyl alcohol (PVA) is selected and added to deionized water at a mass fraction of 1-7 wt%. The solution is dissolved and stirred at 80-95℃ and a stirring speed of 300-500 rpm for 4-8 hours until completely dissolved, yielding a transparent and homogeneous solution. 0.9-3.6 wt% NaCl can be added to enhance ionic conductivity, thus preparing a PVA precursor solution.

[0102] S5. The PVA precursor solution obtained in step S4 is first dip-coated and then spin-coated onto the surface of the PLA nanofiber framework. The spin-coating speed is 500~5000 rpm, the time is 10~30 s, and it is repeated 1~3 times. By controlling the coating thickness, the PVA solution penetrates into the pores of the PLA fibers to form an embedded composite structure that both coats the fiber surface and retains the ventilation channels, thus obtaining a composite membrane.

[0103] S6. Dry the composite membrane from step S5, then freeze it at -30 to -20 °C for 30 to 60 min, and then thaw it at room temperature (24 °C) for 3 to 10 min, which constitutes one freeze-thaw cycle. Use 1 to 6 cycles to form a stable hydrogel network of PVA crystalline regions and hydrogen bond network, thereby enhancing mechanical strength and water content stability.

[0104] S7. Immerse the freeze-thawed composite membrane formed in step S6 into a mixed solution of glycerol and sodium chloride. The concentration of the glycerol solution is 10-50 wt%, and the concentration of sodium chloride is 0.9-3.6 wt%. After soaking for 2-10 minutes, remove the membrane, gently wipe off any residual liquid on the surface, and let it stand for 10 minutes. After this treatment, the glycerol mass fraction inside the membrane is approximately 5-20 wt%, providing hydrophilic adsorption sites and reversible moisture absorption capacity.

[0105] S8. Cut and pattern the breathable conductive hydrogel membrane (BCHN) after freeze-thaw cycles in step S7: Use laser cutting to form the target electrode shape (including circular, strip, or array structure). Deposit a conductive layer on the surface using screen printing. The conductive layer includes any one of Ag / AgCl, Au, Pt, or conductive carbon paste. Connect the signal acquisition module through flexible wires to obtain a breathable conductive hydrogel electrode.

[0106] In this invention, if necessary, a bio-grade pressure-sensitive adhesive can be added as an adhesion layer to the back of the breathable conductive hydrogel electrode to enhance adhesion.

[0107] An exemplary schematic diagram of the fabrication process of a breathable, conductive hydrogel electrode in a typical embodiment of the present invention is shown below. Figure 1 As shown, its preparation process combines hydrogel multilayer composite processing technology compatible with flexible electronics manufacturing processes. Through multiple steps such as electrospinning, spin coating, freeze-thaw crosslinking and electrolyte conditioning, the solvent, temperature, humidity and time are precisely controlled to construct a breathable and conductive hydrogel layer with an embedded reinforcement structure.

[0108] A third aspect of the invention provides the application of the breathable, conductive hydrogel electrode in electrophysiological signal monitoring, sleep analysis, or human-computer interaction.

[0109] In some implementations, the electrophysiological signals include, but are not limited to, one or more of electroencephalogram (EEG), electrocardiogram (ECG), and electromyogram (EMG).

[0110] A fourth aspect of the present invention provides a wearable device comprising the aforementioned breathable, conductive hydrogel electrode.

[0111] A fifth aspect of the present invention provides an electrophysiological signal monitoring system comprising the aforementioned breathable conductive hydrogel electrode.

[0112] A sixth aspect of the present invention provides a method for monitoring electrophysiological signals, comprising:

[0113] Provide the breathable, conductive hydrogel electrode;

[0114] The breathable and conductive hydrogel electrode is attached to the skin surface of the subject, and the electrode array therein is in contact with the subject's skin to collect the subject's electrophysiological signals, which include one or more of electroencephalogram (EEG), electrocardiogram (ECG), and electromyogram (EMG).

[0115] An exemplary schematic diagram of the application scenario of the breathable and conductive hydrogel electrode in a typical embodiment of the present invention is shown below. Figure 2 As shown, it is mainly used for monitoring epidermal physiological electrical signals, such as electroencephalogram (EEG), electromyography (EMG), and electrocardiogram (ECG) signals.

[0116] It should be noted that for experimental steps or conditions not specifically specified in the embodiments of this invention, the procedures or conditions can be performed according to the conventional experimental steps or conditions described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available. The commercial selection of other unmentioned raw materials and instruments is conventional and does not involve the core technical means of this invention.

[0117] For example, the types and sources of the substances used in the embodiments and comparative examples of this invention are as follows:

[0118] Polylactic acid (PLA, Mw≈50,000~300,000), dichloromethane (DCM, analytical grade), N,N-dimethylformamide (DMF, 99.5%), polyvinyl alcohol (PVA, 1799, alcoholysis degree 98%-99%)

[0119] Electrospinning equipment: Yunfan (Tianjin) Instrument Co., Ltd. electrospinning machine (YFSP-T).

[0120] Example 1

[0121] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, as detailed below:

[0122] S1. Polylactic acid (PLA) with a molecular weight of approximately 100,000 was selected as the supporting material. PLA was dissolved in a mixed solvent of dichloromethane (DCM) and N,N-dimethylformamide (DMF) at a ratio of 9:1. The mixture was stirred for 6 hours to obtain a homogeneous polylactic acid solution with a mass fraction of 10 wt% and a mixed solvent mass fraction of 90 wt%.

[0123] S2. The homogeneous polylactic acid solution from step S1 is loaded into a syringe and spun using an electrospinning device at a voltage of 12 kV and a distance of 15 cm between the nozzle and the collecting plate. The injection rate is 1 mm / min. The ambient temperature is 24 ℃ and the relative humidity is 80%. The collection time is 3 minutes, resulting in a porous fiber membrane (PLA membrane) with a thickness of approximately 20 μm, an average fiber diameter of approximately 1 μm, and a porosity of approximately 50%.

[0124] S3. To improve the hydrophilicity of the PLA membrane obtained in step S2, oxygen plasma treatment was performed. The oxygen plasma power was 100W, the treatment time was 60 s, the interval was 120 s, and the treatment was repeated 3 times.

[0125] S4. Polyvinyl alcohol (PVA) was selected and added to deionized water at a mass fraction of 3 wt%. The solution was stirred at 80°C and 300 rpm for 4 hours until completely dissolved, yielding a transparent and homogeneous solution. Then, 0.9 wt% NaCl was added to prepare the PVA precursor solution.

[0126] S5. The PVA precursor solution obtained in step S4 is first dip-coated and then spin-coated onto the surface of the PLA nanofiber framework. The spin-coating speed is 5000 rpm, the time is 30 s, and it is repeated 3 times. By controlling the coating thickness, the PVA solution penetrates into the pores of the PLA fibers to form an embedded composite structure that both coats the fiber surface and retains the ventilation channels, thus obtaining a composite membrane.

[0127] S6. Perform a freeze-thaw cycle on the composite membrane from step S5, freezing it at -30 ℃ for 30 min and then thawing it at room temperature (24 ℃) for 10 min. Four cycles are performed.

[0128] S7. Immerse the freeze-thawed composite membrane from step S6 into a mixed solution of glycerol and NaCl, with a glycerol concentration of 30 wt% and a NaCl concentration of 0.9 wt%. After soaking for 5 min, remove the membrane, gently wipe off any residual liquid on the surface, and let it stand for 10 min. After this treatment, the glycerol mass fraction inside the membrane is approximately 7.5 wt%.

[0129] S8. The breathable conductive hydrogel membrane (BCHN) after freeze-thaw cycles in step S7 is cut and patterned: Laser cutting is used to form the target electrode shape, which is a square structure. A signal acquisition module is connected via flexible wires. A breathable conductive hydrogel electrode is thus obtained, with a thickness of approximately 10 μm.

[0130] The scanning electron microscope image of the breathable conductive hydrogel electrode of this embodiment at 5 μm is shown below. Figure 3 As shown, the rough porous structure of PLA forms a three-dimensional porous framework.

[0131] The scanning electron microscope image of the breathable conductive hydrogel electrode in this embodiment at 2 μm is shown below. Figure 4 As shown, the cross-sectional morphology of the three-dimensional porous skeleton is clearly visible.

[0132] The porosity testing method for the breathable, conductive hydrogel electrode in this embodiment is as follows: The mercury intrusion porosimetry method is used to test the film porosity based on the Washburn equation. Unwetting mercury is injected into the film pores under controlled pressure, and the relationship between pressure and the volume of intruded mercury is recorded. Key parameters such as total porosity and pore size distribution are calculated. This method is suitable for films with pore sizes of 50 nm to 500 μm and follows standards such as ASTM D4404 and ISO 15901-1. The porosity test results are shown in the figure below. Figure 5 As shown, the basis of porous (breathable) properties can be seen.

[0133] The specific method for testing the air permeability of the breathable conductive hydrogel electrode in this embodiment is as follows: The water vapor transmission rate (WVTR) of the membrane is tested using the cup method. The core principle is to calculate the WVTR by measuring the rate of mass change of water vapor passing through the membrane into and out of the test cup under certain temperature and humidity conditions, following national / international standards such as GB / T 1037-2017, ASTM E96, and ISO 2528. Based on the concentration gradient driven mass transfer principle, the membrane to be tested is sealed at the test port of a dedicated permeable cup, creating a stable water vapor concentration difference on both sides of the cup. Deionized water is filled into the cup (the liquid surface is kept at a certain distance from the membrane), creating a saturated water vapor environment inside the cup. Water vapor permeates through the membrane into the low-humidity environment, and the WVTR is calculated by measuring the rate of mass loss of the permeable cup. The air permeability test diagram is shown below. Figure 6 As shown in the figure, the breathable characteristics are directly and objectively demonstrated.

[0134] The mechanical testing method for the breathable, conductive hydrogel electrode in this embodiment is as follows: Mechanical properties were evaluated using a universal testing machine (Instron 3365, Instron, Norwood, MA, USA). During testing, all samples were vertically fixed in the machine handle and then cut from both sides of the polyimide frame with a sharp blade for tensile measurements. The specimen size was 10 mm × 2 mm, and each group was repeated at least three times in parallel. The mechanical test results are shown in the figure below. Figure 7 As shown, the breathable and conductive hydrogel electrode of the present invention is adapted to the skin modulus.

[0135] The bending ability test diagram of the breathable conductive hydrogel electrode in this embodiment is shown in the figure below. Figure 8 As shown, the breathable and conductive hydrogel electrode of the present invention is extremely flexible and can completely conform to the various textures and structures of the skin.

[0136] The impedance testing method for the breathable, conductive hydrogel electrode in this embodiment is as follows: Electrochemical performance was measured using a multi-channel electrochemical workstation (Gamry Instruments, Inc.). Electrochemical impedance spectroscopy (EIS) was performed in the frequency range of 0.1–100,000 Hz, with a DC potential of 0 V and an amplitude of 5 mV. The impedance test graph is shown below. Figure 9 As shown in the figure, the breathable and conductive hydrogel electrode has good conductivity.

[0137] The optical diagram of the breathable, conductive hydrogel electrode in this embodiment is as follows: Figure 10 As shown, the breathable and conductive hydrogel electrode has a clear texture after being applied to the skin, proving its excellent bending performance.

[0138] The specific method for testing the charge injection capability of the breathable, conductive hydrogel electrode in this embodiment is as follows: The measurement is performed using a three-electrode configuration, where the sample serves as the working electrode, a Pt sheet as the counter electrode, an Ag / AgCl wire as the reference electrode, and PBS as the electrolyte. Two 200 ms biphasic pulses with amplitudes of ±0.25 V and ±0.5 V are applied to the installed electrochemical cell. Based on the measured output voltage and current, the CIC of the sample is calculated as CIC = (Qinj(C) + Q(inj(a))) / a, where Qinj(C) is the total charge transported (or injected) in the cathode phase, and Qinj(a) is the total charge transported. The charge injection capability test graph is shown below. Figure 11-13 As shown, the breathable and conductive hydrogel electrode in this embodiment serves as the foundation for the stimulation electrode and is also the basis for the ion-electric conversion of the thin film electrode.

[0139] The voltage tracking capability test method for the breathable conductive hydrogel electrode in this embodiment is as follows: A sinusoidal waveform with an amplitude of 1 Vpp and a frequency range of 0.1 Hz to 10 kHz is applied, and the signal is recorded using an oscilloscope. Channel 1 captures the signal transmitted through the BCHN as the measured voltage, while channel 2 records the original signal as the applied voltage. The voltage tracking capability test diagram is shown below. Figure 14-17 As shown, the input and output voltages of the electrodes are stable, with no voltage attenuation or drift.

[0140] The biocompatibility testing method for the breathable, conductive hydrogel electrode in this embodiment is as follows: The in vitro cell compatibility of the BCHN electrode was evaluated by culturing mouse skin-derived fibroblasts (L929). Cells were cultured at a density of 4 × 10⁶ cells per well. 4 Cells were seeded at a density of 8 × 10⁶ cells / well in 48-well plates containing fibrous hydrogel. Cell viability was assessed by staining with a live / dead dye (Calcein / PI Cell Viability / Cytotoxicity Assay Kit, Beyotime) after 24 and 72 h of culture. Additionally, cells were seeded at a density of 8 × 10⁶ cells / well in each well. 3 Cells were seeded at a density of [number] cells per well into 48-well plates containing fibrous hydrogel to assess cell proliferation. Subsequently, after 24 and 72 hours of culture, cell proliferation was quantitatively analyzed using the Cell Counting Kit-8 (CCK-8, Beyotime). The biocompatibility test results are shown in the figure below. Figure 18 As shown, the electrodes are non-toxic to skin and biological tissues and can be safely applied to the body.

[0141] The specific method for acquiring electromyographic (EMG), electrocardiographic (ECG), and electroencephalographic (EEG) signals using the breathable conductive hydrogel electrodes in this embodiment is as follows: A customized wireless acquisition system based on a Bluetooth module is used for electrophysiological monitoring. Screen-printed BCHN electrodes are used as the sensing interface to ensure close contact with the skin and achieve stable low-impedance coupling. For EEG recording, two electrodes are directly integrated into a headband for use with the Bluetooth module, resulting in a compact, lightweight, and fully portable operation. Data acquisition specifically utilizes the FP1 and FP2 channels of the international 10-20 system, which are particularly sensitive to changes in attention and relaxation states. The wireless system continuously transmits dual-channel electrophysiological signals at a sampling rate of 500 Hz, while onboard synchronization ensures temporal stability during long-term recording. During the experiment, participants experienced predefined conditions including rest, work, and relaxation tasks, enabling the assessment of dynamic changes in EEG under various cognitive states.

[0142] The image shows the in vivo acquisition of muscle electrosignals using the breathable, conductive hydrogel electrode in this embodiment. Figure 19 As shown.

[0143] The in vivo electrocardiogram (ECG) signal acquisition diagram of the breathable, conductive hydrogel electrode in this embodiment is shown below. Figure 20 As shown.

[0144] The in vivo EEG signal acquisition diagram of the breathable, conductive hydrogel electrode in this embodiment is shown below. Figure 21 Show.

[0145] The breathable conductive hydrogel electrode in this embodiment, used to collect EEG signals in vivo, yielded waveforms of alpha, beta, gamma, theta, and delta, as shown in the following figure. Figure 22 As shown.

[0146] Example 2

[0147] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0148] S6. Freeze at -20 ℃ for 60 min, then thaw at room temperature (24 ℃) for 5 min, and repeat the freeze-thaw cycle 6 times.

[0149] The remaining steps are the same as in Example 1.

[0150] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 10 μm.

[0151] Example 3

[0152] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0153] S6. Perform a freeze-thaw treatment on the composite membrane from step S5, then freeze it at -30 ℃ for 30 min, and then thaw it at room temperature (24 ℃) for 8 min, which constitutes one freeze-thaw cycle. One cycle is used.

[0154] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 10 μm.

[0155] Example 4

[0156] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0157] S7: Immerse the freeze-thawed composite membrane in a mixed solution of glycerol and electrolyte. The glycerol solution concentration is 40 wt% and the NaCl concentration is 2 wt%. After soaking for 5 min, remove the membrane, gently wipe off any residual liquid on the surface, and let it stand for 10 min. The glycerol mass fraction inside the membrane is approximately 10 wt%.

[0158] The remaining steps are the same as in Example 1.

[0159] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 10 μm.

[0160] Example 5

[0161] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0162] S7: Immerse the freeze-thawed composite membrane in a mixed solution of glycerol and electrolyte with a glycerol concentration of 50 wt% and a NaCl concentration of 3.6 wt%. After soaking for 1 min, remove the membrane, gently wipe off any residual liquid on the surface, and let it stand for 10 min. The glycerol mass fraction inside the membrane is approximately 10 wt%.

[0163] The remaining steps are the same as in Example 1.

[0164] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 10 μm.

[0165] Example 6

[0166] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0167] S1. Polyurethane was selected as the supporting material. S2. The polyurethane solution was loaded into a syringe, and a fiber network was prepared using an electrospinning device. The voltage was set to 9 kV, the injection rate to 1 mm / min, the ambient temperature to 20 ℃, the relative humidity to 75%, the collection time to 3 min, and the distance between the nozzle and the collection plate to 10 cm. A polyurethane fiber membrane with a thickness of approximately 20 μm, an average fiber diameter of 1.1 μm, and a porosity of approximately 42% was finally obtained.

[0168] The remaining steps are the same as in Example 1.

[0169] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 20 μm.

[0170] Example 7

[0171] This embodiment provides a breathable and conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that: S1, polyhexamethylene adipamide is selected as the support material;

[0172] S2: A polyhexamethylene adipamide solution was loaded into a syringe, and a fiber network was prepared using an electrospinning device. The electrospinning device was operated at a voltage of 15 kV and a distance of 5 cm between the nozzle and the collecting plate, with a feed rate of 2 mm / min. The ambient temperature was 26 ℃ and the relative humidity was 70%. The collection time was 8 minutes, resulting in a polyhexamethylene adipamide porous fiber membrane with a thickness of approximately 12 μm, an average fiber diameter of approximately 1 μm, and a porosity of approximately 45%.

[0173] The remaining steps are the same as in Example 1.

[0174] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 10 μm.

[0175] Example 8

[0176] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0177] S3. To improve the hydrophilicity of the porous fiber membrane from step S2, oxygen plasma treatment was performed. The oxygen plasma power was 50 W, the treatment time was 120 s, the interval was 120 s, and the treatment was repeated 5 times.

[0178] The remaining steps are the same as in Example 1.

[0179] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 10 μm.

[0180] Example 9

[0181] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0182] S3. To improve the hydrophilicity of the porous fiber membrane from step S2, oxygen plasma treatment was performed. The oxygen plasma power was 75 W, the treatment time was 90 s, the interval was 90 s, and the treatment was repeated twice.

[0183] The remaining steps are the same as in Example 1.

[0184] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 10 μm.

[0185] Example 10

[0186] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0187] S5. The PVA precursor solution obtained in step S4 is first dip-coated and then spin-coated onto the surface of the PLA nanofiber framework. The spin-coating speed is 500 rpm and the time is 30 s, repeated 3 times.

[0188] The remaining steps are the same as in Example 1.

[0189] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 80 μm.

[0190] Example 11

[0191] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0192] S5. The PVA precursor solution obtained in step S4 is first dip-coated and then spin-coated onto the surface of the PLA nanofiber framework. The spin-coating speed is 4000 rpm and the time is 10 s. This process is repeated once.

[0193] The remaining steps are the same as in Example 1.

[0194] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 15 μm.

[0195] Example 12

[0196] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0197] S4. Polyvinyl alcohol (PVA) was selected and added to deionized water at a mass fraction of 7 wt%. The solution was stirred at 85°C and 400 rpm for 6 hours until completely dissolved, yielding a transparent and homogeneous solution. Then, 3.6 wt% NaCl was added to prepare the PVA precursor solution.

[0198] The remaining steps are the same as in Example 1.

[0199] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 90 μm.

[0200] Example 13

[0201] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0202] S4. Polyvinyl alcohol (PVA) was selected and added to deionized water at a mass fraction of 1 wt%. The solution was stirred at 95°C and 500 rpm for 4 hours until completely dissolved, yielding a transparent and homogeneous solution. Then, 2 wt% NaCl was added to prepare the PVA precursor solution.

[0203] The remaining steps are the same as in Example 1.

[0204] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 80 μm.

[0205] Example 14

[0206] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0207] S4. Polyacrylamide was selected and added to deionized water at a mass fraction of 3 wt%. The solution was stirred at 80°C and 300 rpm for 4 hours until completely dissolved, yielding a transparent and homogeneous solution. Then, 0.9 wt% KCl was added to prepare the hydrogel precursor solution.

[0208] S7. Immerse the freeze-thawed composite membrane formed in step S6 into a mixed solution of propylene glycol and KCl, with a propylene glycol concentration of 30 wt% and a KCl concentration of 0.9 wt%. After soaking for 5 min, remove the membrane, gently wipe off any residual liquid on the surface, and let it stand for 10 min. After this treatment, the propylene glycol mass fraction in the membrane is approximately 8.5 wt%.

[0209] The remaining steps are the same as in Example 1.

[0210] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 120 μm.

[0211] Example 15

[0212] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0213] S4. Polyacrylic acid was selected and added to deionized water at a mass fraction of 3 wt%. The solution was stirred at 80°C and 300 rpm for 4 hours until completely dissolved, resulting in a transparent and homogeneous solution. Then, 0.9 wt% CaCl2 was added to prepare the hydrogel precursor solution.

[0214] S7. Immerse the freeze-thawed composite membrane formed in step S6 into a mixed solution of butanediol and CaCl2, with a butanediol concentration of 30 wt% and a CaCl2 concentration of 0.9 wt%. After soaking for 5 min, remove the membrane, gently wipe off any residual liquid on the surface, and let it stand for 10 min. After this treatment, the mass fraction of butanediol in the membrane is approximately 8.2 wt%.

[0215] The remaining steps are the same as in Example 1.

[0216] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 115 μm.

[0217] Example 16

[0218] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0219] S4. Alginate was selected and added to deionized water at a mass fraction of 3 wt%. The solution was dissolved and stirred at 80°C and 300 rpm for 4 hours until completely dissolved, yielding a transparent and homogeneous solution. Then, 0.9 wt% MgCl2 was added to prepare the hydrogel precursor solution.

[0220] S7. Immerse the freeze-thawed composite membrane from step S6 into a mixed solution of polyethylene glycol and MgCl2, where the polyethylene glycol concentration is 30 wt% and the MgCl2 concentration is 0.9 wt%. After immersion for 5 min, remove the membrane, gently wipe off any residual liquid, and allow it to stand for 10 min. After this treatment, the polyethylene glycol mass fraction in the membrane is approximately 7.8 wt%.

[0221] The remaining steps are the same as in Example 1.

[0222] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 125 μm.

[0223] Example 17

[0224] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0225] S4. Select gelatin and add it to deionized water at a mass fraction of 3 wt%. Dissolve and stir at 80℃ and 300 rpm for 4 hours until completely dissolved to obtain a transparent and homogeneous solution. Add 0.9 wt% LiCl to prepare the hydrogel precursor solution.

[0226] S7. Immerse the freeze-thawed composite membrane formed in step S6 into a mixed solution of betaine and LiCl, with a betaine concentration of 30 wt% and a LiCl concentration of 0.9 wt%. After soaking for 5 min, remove the membrane, gently wipe off any residual liquid on the surface, and let it stand for 10 min. After this treatment, the betaine mass fraction in the membrane is approximately 8 wt%.

[0227] The remaining steps are the same as in Example 1.

[0228] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 118 μm.

[0229] Example 18

[0230] This embodiment provides a breathable, conductive hydrogel electrode and its preparation method, which differs from Embodiment 1 in that:

[0231] S4. Chitosan was selected and added to deionized water at a mass fraction of 3 wt%. The solution was dissolved and stirred at 80°C and 300 rpm for 4 hours until completely dissolved, yielding a transparent and homogeneous solution. Then, 0.9 wt% phosphate buffer solution was added to prepare the hydrogel precursor solution.

[0232] The remaining steps are the same as in Example 1.

[0233] The thickness of the breathable and conductive hydrogel electrode prepared in this embodiment is approximately 122 μm.

[0234] Comparative Example 1

[0235] This comparative example provides a breathable, conductive hydrogel electrode and its preparation method. The difference from Example 1 is that it does not contain a porous fiber support structure; the hydrogel electrode is directly prepared, as detailed below:

[0236] S1, same as S4 in Example 1, 3 wt% PVA + 0.9 wt% NaCl, stirred at 80℃ and 300 rpm for 4 hours.

[0237] S2. Spin-coat the precursor solution onto the glass substrate (5000 rpm, 30 s, repeat 3 times).

[0238] S3, same as S6 in Example 1, freeze at -30℃ for 30 min + thaw at room temperature for 10 min, repeat 4 times.

[0239] S4, same as S7 in Example 1, 30wt% glycerol + 0.9wt% NaCl, soak for 5 min.

[0240] S5. Cut into a square structure, add pressure-sensitive adhesive to the back to obtain a pure hydrogel electrode.

[0241] Defect Description: Lacks fiber support structure, poor mechanical properties (easily broken), lacks three-dimensional through-holes, extremely poor air permeability (water vapor transmission rate <0.4 kg). m - ² day - ¹), when worn, sweat accumulates severely, and moisture loss exceeds 50% within 7 days.

[0242] Comparative Example 2

[0243] This comparative example provides a breathable, conductive hydrogel electrode and its preparation method. The difference from Example 1 is that the oxygen plasma hydrophilic treatment step S3 is omitted, while the remaining steps are completely consistent with Example 1.

[0244] Defect Description: PLA fiber surface has no hydrophilic groups, the adhesion between hydrogel and fiber is weak and easy to peel off; hydrogel cannot penetrate into the fiber interior and cannot form an embedded reinforcement structure, resulting in severe interface slippage; contact impedance is not less than 10 kΩ, signal-to-noise ratio is <15dB during signal acquisition, and signal drift is obvious after long-term wear.

[0245] Comparative Example 3

[0246] This comparative example provides a breathable, conductive hydrogel electrode and its preparation method. The difference from Example 1 is that the glycerol concentration in the post-treatment solution is adjusted to 65wt% (traditional high moisturizing formula), while the remaining steps are the same as in Example 1.

[0247] Defect Description: Intramembrane glycerol mass fraction >50 wt%, hydrogel texture is sticky and poor wearing comfort; electrolyte is excessively diluted, ion migration resistance is increased, impedance at 1 kHz >1 kΩ, contact impedance >15 kΩ; severe distortion during electrophysiological signal acquisition, electromyographic signal noise is large and peak is blurred.

[0248] Comparative Example 4

[0249] This comparative example provides a breathable and conductive hydrogel electrode and its preparation method. The difference from Example 1 is that S5 only uses dip coating and does not have a spin coating step. The remaining steps are the same as in Example 1.

[0250] Defect Description: The hydrogel is unevenly coated on the fiber surface with large thickness variations (30-50 μm); it is difficult to penetrate the three-dimensional interconnected channels inside the fiber, forming only a surface coating layer and failing to form an embedded reinforcing structure; the gas transport channels are blocked, and the water vapor permeability is <0.5 kg. m - ² day - ¹; When worn, due to insufficient mechanical locking at the interface, signal noise increases significantly during movement, with a signal-to-noise ratio of <15dB.

[0251] Comparative Example 5

[0252] This comparative example provides a breathable and conductive hydrogel electrode and its preparation method. The difference from Example 1 is that the composite film in step S5 is dried and then frozen at -40 °C for 70 min, with 8 freeze-thaw cycles. The remaining steps are completely consistent with Example 1.

[0253] Defect Description:

[0254] Hydrogel network structure disruption: The excessively low freezing temperature (-40℃) caused excessive crystallization of PVA molecular chains, and the excessively long freezing time (70min) exacerbated the aggregation of crystal regions. The superimposed excessive number of cycles (8 times) caused the hydrogen bond network inside the hydrogel to break and the pore structure to collapse, making it impossible to form a continuous ion conduction pathway.

[0255] Mechanical property deterioration: Excessive freeze-thaw cycles reduce the interfacial bonding force between the hydrogel and the porous fiber support structure, increasing the brittleness of the composite membrane, which is prone to cracking due to minor skin movements during wear.

[0256] Decreased conductivity and signal acquisition performance: Crystallization and network collapse hinder ion migration, impedance rises to 125Ω at 1kHz, and contact impedance reaches 7.2kΩ; signal-to-noise ratio is only 18dB during electrophysiological signal acquisition, alpha and beta waves are difficult to identify in EEG signals, and ST segment drift is obvious in ECG signals.

[0257] Performance testing

[0258] The performance of the breathable and conductive hydrogel electrodes prepared in Examples 1-5 and Comparative Examples 1-5 was tested, and the specific test results are shown in Table 1.

[0259] The performance testing method of this invention is as follows:

[0260] Impedance: Electrochemical performance was measured using a multichannel electrochemical workstation (Gamry Instruments, Inc.). Electrochemical impedance spectroscopy (EIS) was performed in the frequency range of 0.1–100,000 Hz, with a DC potential of 0 V and an amplitude of 5 mV.

[0261] Contact impedance: A multi-channel electrochemical workstation (Gamry Instruments, Inc.) was used with an Ag / AgCl reference electrode. The electrode to be tested was cut into a circle with a diameter of 8 mm (a common size for skin contact), and a flexible wire was connected to the back, ensuring good contact between the wire and the electrode without loosening. At room temperature (25±2 ℃) and relative humidity (50±5 %), the inner forearm skin of a healthy volunteer (clean, dry, and without damage) was selected as the test interface. The electrode to be tested was attached to the skin surface using bio-grade pressure-sensitive adhesive, and the reference electrode was attached to the distal end of the same side arm. Slight pressure (approximately 50 g / cm²) was applied to ensure a tight fit without air bubbles. The sampling rate of the acquisition system was set to 1 kHz, and the acquisition time was 10 min. The contact impedance between the electrode and the skin was calculated using the system's built-in impedance analysis module. Each sample was tested repeatedly in three different skin regions, and the average value was taken.

[0262] Water vapor transmission rate (WVTR): Place 20g of deionized water in a glass bottle in a 30°C oven. Measure the weight loss of different bottles every 24 hours. WVTR can be obtained using the equation:

[0263]

[0264] Where mloss, t, and S are the weight of water loss, time, and surface area, respectively.

[0265] Signal-to-noise ratio (SNR): The raw signals were filtered using Matlab software (EEG 0.5~30 Hz, ECG 0.5~40 Hz, EMG 10~500 Hz), and the peak signal value (V_signal) was extracted. Noise signals were collected during periods without signal acquisition (electrodes not in contact with the skin but maintaining the same testing environment), and the effective noise value (V_noise) was extracted. The SNR was calculated using the following formula:

[0266]

[0267] The unit is dB. Each signal type was tested 3 times and the average value was taken.

[0268] Table 1 Performance test results of breathable conductive hydrogel electrodes of Examples 1-18 and Comparative Examples 1-5

[0269]

[0270] The electrode prepared by the above steps has an impedance of no more than 100 Ω at 1 kHz, a contact impedance as low as 0.2~5 kΩ, and a water vapor transmission rate (WVTR) of 0.9~2.2 kg·m. - ²·day - ¹, with a moisture loss rate of less than 15% within 14 days, and a signal-to-noise ratio that can be maintained at >19 dB for a long period (more than two months) in EEG, ECG, and EMG monitoring, exhibiting excellent breathability, stability and physiological comfort, and can be widely used in fields such as fatigue driving monitoring, sleep analysis and intelligent human-computer interaction.

[0271] In addition, with reference to the foregoing embodiments, experiments were conducted using other raw materials, process operations, and process conditions described in this specification, and all yielded relatively ideal results.

[0272] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A breathable, conductive hydrogel electrode, characterized in that, include: A porous fiber support structure has a three-dimensional porous structure formed by interwoven porous fibers. The porous fibers have a three-dimensional through-hole structure, which is formed by interconnected pores distributed on the surface and inside of the porous fibers. A hydrogel conductive network is distributed on the surface and inside of the porous fiber support structure to form a continuous ion conduction path inside the electrode. The hydrogel conductive network is also partially embedded in a local area of ​​the three-dimensional through-hole structure, thereby forming an interlaced and continuously coupled embedded reinforcement structure at the microscale, and retaining gas transmission channels within the three-dimensional through-hole structure. The method for preparing the breathable, conductive hydrogel electrode includes: An organic fiber network is provided, which has a three-dimensional porous structure formed by interwoven organic fibers; The organic fiber network is subjected to hydrophilic treatment to transform the organic fibers into porous fibers, and hydrophilic groups are introduced at least on the surface of the porous fibers to obtain a porous fiber support structure. A hydrogel precursor solution is applied to the porous fiber support structure, and a portion of the hydrogel precursor solution enters the interior of the porous fiber support structure. Then, a freeze-thaw cycle is performed to obtain a freeze-thaw molded body. The electrode is obtained by immersing the freeze-thawed body in a post-treatment solution and then removing it, wherein the post-treatment solution contains a humectant and at least one of the hydrogel precursor solution and the post-treatment solution contains an electrolyte.

2. The breathable and conductive hydrogel electrode according to claim 1, characterized in that: The diameter of the porous fiber is 1~3μm; And / or, the porosity of the porous fiber is above 50%; And / or, the porous fiber is made of at least one of polylactic acid, polyurethane, and polyhexamethylene adipamide; And / or, the aperture of the pores contained in the three-dimensional through-hole structure is 100~400nm; And / or, the porosity of the porous fiber support structure is 30% or more; And / or, the pore size of the porous fiber support structure is 1~3μm; And / or, the hydrogel conductive network comprises a polymer hydrogel network and electrolytes and humectants uniformly distributed within the polymer hydrogel network; And / or, the thickness of the breathable conductive hydrogel electrode is 10~125 μm.

3. The breathable and conductive hydrogel electrode according to claim 2, characterized in that: The porosity of the porous fiber is 70-80%; And / or, the porosity of the porous fiber support structure is 40-50%; And / or, the network framework material of the polymer hydrogel network includes at least one of polyvinyl alcohol, polyacrylamide, polyacrylic acid, alginate, gelatin, and chitosan; And / or, the electrolyte includes at least one of NaCl, KCl, CaCl2, MgCl2, LiCl, and phosphate buffered saline (PBS); And / or, the moisturizer includes at least one of glycerin, propylene glycol, butylene glycol, polyethylene glycol, and betaine; And / or, the hydrogel conductive network comprises 86.7~94.1 wt% polymer hydrogel network, 0.9~3.6 wt% electrolyte and 5~10 wt% humectant; And / or, the mass ratio of the porous fiber support structure to the hydrogel conductive network is 2~4:6~8; And / or, the thickness of the porous fiber support structure is 10~80μm; And / or, the thickness of the hydrogel covering the surface of the porous fiber support structure is 5~20μm; And / or, the breathable conductive hydrogel electrode has an impedance of 10~100Ω at 1 kHz, a contact impedance of 0.2~5 kΩ, and a water vapor permeability of 0.9~2.2 kg·m. -2 ·day -1 The moisture loss rate within 14 days shall not exceed 15%; And / or, the breathable conductive hydrogel electrode has a signal-to-noise ratio >19 dB in electrophysiological signal monitoring.

4. The breathable and conductive hydrogel electrode according to claim 1, characterized in that, include: The organic fiber network is prepared by at least electrospinning. And / or, the organic fiber network is subjected to the hydrophilic treatment using oxygen plasma; And / or, at least dip coating and / or spin coating are used to apply the hydrogel precursor solution to the porous fiber support structure; And / or, the freeze-thaw cycle treatment includes: freezing at -30 to -20 °C for 30 to 60 min, then thawing at room temperature for 3 to 10 min, and repeating the freeze-thaw cycle 1 to 6 times; And / or, the preparation method includes: immersing the freeze-thawed body in a post-treatment solution for 0.5 to 5 minutes; And / or, the preparation method further includes: patterning or arraying the post-processed freeze-thawed body to form a target electrode.

5. The breathable and conductive hydrogel electrode according to claim 4, characterized in that, The electrospinning specifically includes: providing an electrospinning solution with a concentration of 9~10wt%, setting a voltage of 9~15kV, a injection rate of 1~2 mm / min, an ambient temperature of 20~26 ℃, a relative humidity of 70~80%, a collection time of 0.5~8min, and a distance of 5~15cm between the nozzle and the collection plate; And / or, set the power of the oxygen plasma to 50~100W, and make the oxygen plasma intermittently contact the organic fiber network 2~5 times, with each contact lasting 1~2 minutes and the interval time being 1~3 minutes; And / or, the hydrogel precursor solution is first dip-coated and then spin-coated onto the surface of the porous fiber support structure, controlling the spin-coating speed to be 500~5000 rpm and the time to be 10~30 s, repeated 1~3 times, and then the freeze-thaw cycle treatment is performed. And / or, the hydrogel precursor solution contains 1-7 wt% polyvinyl alcohol and 0.9-3.6 wt% a first electrolyte; And / or, the post-treatment solution contains 10-50 wt% glycerol and 0.9-3.6 wt% a second electrolyte.

6. The breathable and conductive hydrogel electrode according to claim 5, characterized in that: The electrospinning solution comprises 9-10 wt% polylactic acid and 90-91 wt% organic solvent; And / or, the shape of the target electrode includes any one of a circular structure, a strip structure, and an array structure; And / or, the method for preparing the hydrogel precursor solution includes: stirring a mixed solution containing the polyvinyl alcohol and the electrolyte at a stirring speed of 300-500 rpm at 80-95 °C for 4-8 h to obtain the hydrogel precursor solution.

7. The breathable and conductive hydrogel electrode according to claim 6, characterized in that: The organic solvent includes a combination of dichloromethane and N,N-dimethylformamide, wherein the mass ratio of dichloromethane to N,N-dimethylformamide is 88~92:8~12; And / or, the molecular weight of the polylactic acid is 50,000 to 300,000.

8. The application of the breathable conductive hydrogel electrode according to any one of claims 1-7 in electrophysiological signal monitoring, sleep analysis or human-computer interaction.

9. The application according to claim 8, characterized in that: The electrophysiological signals include one or more of the following: electroencephalogram (EEG), electrocardiogram (ECG), and electromyogram (EMG).

10. A wearable device, characterized in that, Includes the breathable, conductive hydrogel electrode according to any one of claims 1-7.

11. An electrophysiological signal monitoring system, characterized in that, Includes the breathable, conductive hydrogel electrode according to any one of claims 1-7.

12. A method for monitoring electrophysiological signals, characterized in that, include: Provides a breathable, conductive hydrogel electrode according to any one of claims 1-7; The breathable and conductive hydrogel electrode is attached to the skin surface of the subject, and the electrode array therein is in contact with the subject's skin to collect the subject's electrophysiological signals, which include one or more of electroencephalogram (EEG), electrocardiogram (ECG), and electromyogram (EMG).

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