Conductive hydrogel and preparation method thereof

Abstract

The invention relates to the technical field of functional polymer materials, in particular to conductive hydrogel and a preparation method thereof.Polyvinyl alcohol-sodium carboxymethyl cellulose serves as a composite polymer matrix, silver elementary substance particles and MXene are matched to construct a point-sheet synergistic conductive network, and the conductive hydrogel is prepared; the interface compatibility is optimized by virtue of a triphenyl phosphite, sodium tetraborate and sodium silicate composite modifier, and the conductivity and mechanical properties are synergistically improved in combination with a multi-stage composite filler consisting of epoxy modified nano silicon dioxide / silver particles, modified MXene and modified montmorillonite; meanwhile, through an integrated process of low-temperature 3D printing precise forming, freezing-unfreezing circulation cross-linking strengthening structure and segmented vacuum drying for regulating and controlling moisture stability, the problem that the conductivity and the mechanical property of traditional conductive hydrogel are difficult to consider at the same time is solved; the method is suitable for the fields of flexible sensors, electronic skin, biomedical signal acquisition electrodes, wearable flexible electronic equipment and the like, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional polymer materials, and particularly relates to a conductive hydrogel and a preparation method thereof. BACKGROUND

[0002] A hydrogel is a kind of functional material formed by a three-dimensional network structure of polymer molecules through physical or chemical cross-linking, and the network structure can stably adsorb and retain a large amount of water, so it has excellent flexibility, elasticity and biocompatibility, and shows basic application value in the fields of flexible devices and biomedicine. A conductive hydrogel is a material that introduces a conductive component (such as a conductive particle or a conductive polymer) into the three-dimensional network of the hydrogel, so that the material has both the flexibility of the hydrogel and the conductivity. The core reason why this kind of material needs to have conductivity is to meet the signal transmission and response requirements in specific scenarios. For example, in a flexible sensor, the conductive performance can realize the conversion and transmission of external stimuli (such as pressure and strain) to an electrical signal. In the field of biomedical sensing, the conductive property can support the collection and conduction of electrophysiological signals (such as electrocardiogram and electromyogram). Therefore, the conductive hydrogel becomes a key material connecting flexible carriers and functional applications.

[0003] In the prior art, the conductive hydrogel generally faces the core problem of difficult optimization of conductivity and mechanical performance. In order to improve the conductivity, the existing scheme usually increases the amount of conductive filler, and improves the electrical conductivity by constructing a denser conductive path. However, with the increase of the content of the conductive filler, the filler particles are prone to agglomeration in the polymer matrix, which destroys the original three-dimensional network integrity of the hydrogel, causing stress concentration points in the material. This structural defect will directly cause the mechanical performance of the hydrogel to decrease significantly, which is specifically manifested in the decrease of material flexibility, easy breaking during stretching, and poor fatigue resistance. For example, when subjected to repeated bending or stretching, the agglomeration area of the filler is prone to crack, which not only further damages the conductive network and causes a sharp drop in electrical conductivity, but also shortens the service life of the material. If the amount of conductive filler is reduced to ensure the mechanical performance, the lack of conductive paths will lead to the inability to meet the actual application requirements of the electrical conductivity. This performance contradiction between conductivity and mechanics makes the existing conductive hydrogel difficult to adapt to scenarios (such as wearable flexible sensors and flexible electronic skins) that require both stable conductivity and reliable mechanical performance, which seriously limits its application range.

[0004] Therefore, according to the related technology in the above, it is urgent to develop a conductive hydrogel and a preparation method thereof. SUMMARY

[0005] Therefore, according to the related technology in the above, it is urgent to develop a conductive hydrogel and a preparation method thereof.

[0006] Based on the above purpose, the present application provides a kind of conductive hydrogel and its preparation method.

[0007] A kind of conductive hydrogel is prepared from the following mass parts raw materials: polymer matrix 40-70 parts, conductive filler 5-20 parts, crosslinking agent 1-5 parts, mixed solvent 80-150 parts, composite modifier 8-25 parts, composite filler 2-8 parts, dispersant 2-6 parts, anti-aging agent 0.3-1.0 parts; The mixed solvent is water / dimethyl sulfoxide mixed solvent, and the volume ratio of water and dimethyl sulfoxide in the water / dimethyl sulfoxide mixed solvent is 1:2-3; The composite modifier is prepared from triphenyl phosphite, sodium tetraborate and sodium silicate in a mass ratio of 3-8:4-8:6-12; The composite filler is prepared from epoxy-modified nano-SiO2 / silver particles, modified MXene and modified montmorillonite in a mass ratio of 3.5-4.5:1.5-2.5:0.8-1.2, the polymer matrix provides a three-dimensional network skeleton for the hydrogel, and supports the basic structure of the material; the conductive filler can construct a conductive path in the network, giving the material conductive ability; the crosslinking agent can promote the crosslinking of polymer molecules and enhance the stability of the network structure; the water / dimethyl sulfoxide mixed solvent can dissolve and disperse each raw material, and adjust the solubility and fluidity of the system; the composite modifier can improve the interfacial compatibility of the filler and the matrix, and reduce the aggregation of the components; the composite filler can synergistically improve the mechanical strength and conductive performance of the material, and make up for the performance defects of a single filler; the dispersant can prevent the aggregation of the conductive filler and the composite filler, and ensure their uniform dispersion; the anti-aging agent can inhibit the oxidative aging of the material during long-term use, and prolong the service life.

[0008] Preferably, the polymer matrix is a polyvinyl alcohol and sodium carboxymethyl cellulose composite system; the polyvinyl alcohol has a degree of polymerization of 1700-2000, and the sodium carboxymethyl cellulose has a degree of substitution of 0.6-0.8; in the polyvinyl alcohol and sodium carboxymethyl cellulose composite system, the mass ratio of polyvinyl alcohol to sodium carboxymethyl cellulose is 6-9:1; the polyvinyl alcohol has good flexibility and film-forming property, which can ensure the elasticity and mechanical basis of the hydrogel; the sodium carboxymethyl cellulose can improve the water absorption capacity and mechanical support of the material, and the combination of the two can balance flexibility and strength; the polyvinyl alcohol with a specific degree of polymerization can ensure its solubility in the mixed solvent and crosslinking effect, the sodium carboxymethyl cellulose with a specific degree of substitution can optimize its compatibility with polyvinyl alcohol, and a specific mass ratio can further realize the synergy of the properties of the two polymers, avoiding the performance short board caused by a single polymer.

[0009] Preferably, the conductive filler is an electronic conductive filler; the electronic conductive filler is a mixture of silver elemental particles and MXene; the average particle size of the silver elemental particles is 100-300 nm, the MXene has a sheet thickness of ≤5 nm and a lateral size of 1-5 μm, the electronic conductive filler realizes material conductivity through electron conduction, the silver elemental particles have excellent conductivity, small particle size makes them easy to disperse in the matrix and construct dense conductive nodes; the MXene sheet has high conductivity and a two-dimensional sheet structure, and can build a continuous conductive path, and the mixture of the two can form a "point-sheet" synergistic conductive network to improve the conductivity stability; the silver particles and MXene with specific particle size and size can avoid agglomeration, while ensuring the continuity of the conductive path and preventing fluctuations in the conductivity caused by improper filler size.

[0010] Preferably, the crosslinking agent is a mixture of polyethylene glycol diacrylate and borax; the dispersant is polyvinylpyrrolidone; and the anti-aging agent is hindered phenol BHT. Polyethylene glycol diacrylate can enhance the stability of the polymer network through chemical crosslinking, and borax can form dynamic coordination crosslinking with polyvinyl alcohol to adjust the flexibility and self-healing property of the material. The mixture of the two can flexibly control the crosslinking density and balance the strength and elasticity of the material. Polyvinylpyrrolidone has good dispersibility and can prevent the agglomeration of conductive fillers through steric hindrance effect to ensure uniform distribution of the fillers. Hindered phenol BHT as a classic anti-aging agent can capture free radicals generated during the aging process of the material, inhibit oxidative degradation, and delay the performance degradation of the material.

[0011] Preferably, the preparation method of the epoxy-modified nano-SiO2 / silver particles is as follows: Step A1. Mix nano-SiO2 and silver nanoparticles at a mass ratio of 3-5:1, crush to 100-120 mesh, and obtain a mixed powder; Step A2. Prepare a KH-560 ethanol solution with a mass fraction of 2%-4%, mix the mixed powder and the KH-560 ethanol solution at a mass ratio of 100:15-25, and add to a reaction kettle; Step A3. Control the temperature of the reaction kettle at 50-60℃ and the rotation speed at 300-400 r / min, and stir for 30-40 min; Step A4. After the reaction is completed, filter, wash with anhydrous ethanol 2-3 times, dry in a vacuum oven at 70-80°C for 2-3 h to obtain epoxy-modified nano-SiO2 / silver particles. Step A1 mixes and crushes to preliminarily mix the nano-SiO2 and silver nanoparticles uniformly, and a particle size of 100-120 meshes ensures sufficient subsequent modification; Step A2, KH-560 contains an epoxy group, which can be uniformly attached to the surface of the mixed powder through an ethanol solution, providing active sites for subsequent bonding with the matrix; the temperature and speed of Step A3 can ensure that the KH-560 and the powder are fully reacted, avoiding poor modification effect caused by incomplete reaction; Step A4 washing can remove unreacted KH-560 and impurities, and vacuum drying can avoid powder oxidation. The finally obtained epoxy-modified filler can significantly improve the interfacial bonding force with the polymer matrix and enhance the mechanical and conductive synergy of the material.

[0012] Preferably, the preparation method of the modified MXene is as follows: Step B1. Disperse the MXene layers in deionized water, add 1%-3% by mass of dopamine solution, and stir at 30-40°C for 6-8h. The solvent of the dopamine solution should be consistent with the dispersion medium, i.e. deionized water; Step B2. Add 0.5%-1.5% by mass of silane coupling agent KH-550, and continue stirring for 2-3h; Step B3. Centrifugal separation, wash with deionized water 3-4 times, and dry at 60-70°C for 4-5h to obtain modified MXene. In Step B1, dopamine can self-polymerize on the surface of MXene to form a polydopamine coating, improving the dispersibility and hydrophilicity of MXene and avoiding layer agglomeration. In Step B2, the amino group of KH-550 can react with the active groups of polydopamine to further introduce organic functional groups, enhancing the compatibility of MXene with the polymer matrix. Step B3 centrifugal washing can remove unreacted dopamine and KH-550, and vacuum drying can ensure the stability of the modified MXene. The final product can better integrate into the polymer network, improving the continuity of the conductive path and the mechanical support effect.

[0013] Preferably, the preparation method of the modified montmorillonite is as follows: Step C1. Take sodium-based montmorillonite and add 2% hydrochloric acid solution, mechanically stir at 50°C for 5h, centrifugal separation, and wash with water until AgN Titration without precipitation, vacuum drying at 60°C for 24h, and grinding through a 100-mesh sieve to obtain hydrochloric acid-activated montmorillonite; Step C2. Mix hydrochloric acid-activated montmorillonite with hexadecyltrimethylammonium bromide at a mass ratio of 100:40, add deionized water, mechanically stir at 65°C for 24 hours, centrifuge and discard the supernatant, wash with water until no foam is present, vacuum dry at 60°C for 24 hours, grind and pass through a 100-mesh sieve to obtain modified montmorillonite. Step C1, hydrochloric acid activation, can remove impurity ions from montmorillonite, expand the interlayer spacing, increase active sites, and enhance its adsorption and binding capacity. In step C2, hexadecyltrimethylammonium bromide, as an organic modifier, can insert into the interlayer of montmorillonite, improve its compatibility with the organic polymer matrix, and prevent inorganic montmorillonite from agglomerating in the matrix. Two centrifugation and washing processes ensure thorough removal of impurities, and drying, grinding, and sieving ensure uniform particle size of the modified montmorillonite. The final product can enhance the mechanical strength of the polymer network and improve the tensile and deformation resistance of the material.

[0014] Preferably, the conductive hydrogel is prepared as follows: Step S1. Raw material pretreatment: The polymer matrix is ​​pulverized to 80-100 mesh and dried at 100-110℃ for 1.5-2.5h, with the moisture content controlled at ≤5%; the conductive filler and dispersant are mixed and ultrasonically dispersed for 15-20min to form a uniform dispersion. Step S2. Construction of pre-crosslinked system: Add the uniformly dispersed liquid to the kneader, add the mixed solvent, stir evenly, add the composite modifier, control the temperature at 20-30℃ and the speed at 300-400r / min, stir for 30-60min, then add the crosslinking agent, adjust the water content of the system to 7%-12%, and obtain the pre-crosslinked system; Step S3. Composite reinforcement and conductive functionalization: Add composite filler to the pre-crosslinked system, heat to 40-50℃, stir for 30-40 min, add electronic conductive filler dispersion, keep warm and stir for 30-50 min to obtain functionalized system; Step S4. Molding and post-processing: inject the functionalized system into the mold and form by low-temperature 3D printing, crosslinking by freeze-thaw cycle, freezing temperature -18--20℃, freezing time 10-12h, thawing temperature room temperature, thawing time 2-4h; after molding, soak in deionized water for 4-6 days, change water every 12h, add anti-aging agent, vacuum drying at 80-90℃, vacuum degree -0.09--0.07MPa for 6-10h, obtain the conductive hydrogel; the polymer crushing and drying in step S1 can reduce the interference of water on the subsequent crosslinking reaction, and ensure the stability of the reaction; the ultrasonic dispersion of the conductive filler and the dispersant can break the agglomeration by ultrasonic vibration, and form a uniformly dispersed liquid, laying a foundation for subsequent conductive network construction; the kneader stirring in step S2 can fully mix the components, the interfacial modification effect of the composite modifier is played at the appropriate temperature and speed, the crosslinking agent constructs a preliminary three-dimensional network, and the water content is adjusted to control the crosslinking degree, avoiding the influence of over-drying or over-wetting on the performance; the warming and stirring in step S3 is beneficial to the uniform dispersion of the composite filler and the full combination with the pre-crosslinking system, enhancing the mechanical properties, and the addition of the conductive filler dispersion liquid can further improve the conductive network and enhance the conductive performance; the low-temperature 3D printing in step S4 can realize precise molding of complex structures, and the freeze-thaw cycle can promote further crosslinking of polymer molecules and enhance the stability of the network; soaking in deionized water can remove unreacted raw materials and impurities, improving the purity of the material; vacuum drying can control the final water content to ensure the flexibility and conductive stability of the material, and the anti-aging agent prolongs the service life of the material.

[0015] Preferably, in the low-temperature 3D printing molding in step S4, the rheological properties of the printing ink satisfy: the viscosity is 1000-3000mPa·s at 25℃ under shear rate 1-10s -1 , with shear thinning characteristics; the printing parameters are: extrusion rate 0.5-1.2mm / s, printing nozzle inner diameter 0.4-0.8mm, printing platform temperature -20--15℃, printing layer number 5-10 layers, each layer thickness 0.2-0.4mm; the specific rheological properties can ensure that the viscosity of the printing ink decreases when extruding (under shear), facilitating smooth extrusion, and the viscosity rises after stopping extrusion, ensuring the shape retention of the molded part and avoiding collapse; suitable extrusion rate and nozzle inner diameter can prevent ink blockage or excessive extrusion, ensuring printing accuracy; the low-temperature printing platform can quickly cool the ink, further improving the structural stability of the molded part; the specific layer number and layer thickness can balance the structural strength and flexibility of the material, avoiding insufficient strength due to too few layers or uneven printing due to too large layer thickness.

[0016] Preferably, the vacuum drying in step S4 adopts segmented temperature control: the first stage is 78-82℃ for 3-4h to remove surface moisture, and the second stage is 88-92℃ for 3-6h to remove bound water. Among them, the low-temperature drying in the first stage can slowly remove the surface moisture of the material, avoid the shrinkage deformation of the material due to the rapid evaporation of water, and ensure the structural integrity; the high-temperature drying in the second stage can effectively remove the bound water inside the material, accurately control the final water content, avoid the decrease of the conductivity due to too much bound water or the embrittlement of the material due to too little bound water, and ensure that the hydrogel has good flexibility and stable conductivity at the same time.

[0017] The beneficial effects of the present application are: The present application provides a kind of conductive hydrogel and preparation method thereof, the present application is by optimizing polyvinyl alcohol-sodium carboxymethyl cellulose composite polymer matrix ratio to lay the foundation for flexible and stable structure, introduce silver single particle-MXene composite conductive filler constructs "point-plate" synergistic conductive network, with triphenyl phosphite-sodium tetraborate-sodium silicate composite modifier improves the interface compatibility of filler and matrix, adopt epoxy modified nano SiO2 / silver particle-modified MXene-modified montmorillonite multi-level composite filler realizes the synergistic enhancement of conductivity and mechanical property, combined with low temperature 3D printing forming, freezing-thawing cycle crosslinking and segmented vacuum drying process, compared with prior art, effectively solve the core contradiction of traditional conductive hydrogel "the mechanical property is reduced when the conductivity is improved", the prepared conductive hydrogel has high conductivity and stable conductivity in long-term use, excellent tensile strength and elongation at break, significantly enhanced anti-aging ability (high performance retention rate after heat aging), can also realize high-precision forming of complex structure, and has good water content stability and mechanical cycle stability, can be used in the field of flexible sensor, electronic skin, biomedical signal acquisition electrode, wearable flexible electronic device, etc., has wide application prospect. DETAILED DESCRIPTION

[0018] To make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below with specific examples.

[0019] Example 1: a preparation method of a conductive hydrogel, comprising the following steps: P1. Polymer matrix preparation: take polyvinyl alcohol with a degree of polymerization of 1700-2000 and sodium carboxymethyl cellulose with a degree of substitution of 0.6-0.8, mix them in a mass ratio of 6:1, crush to 80-100 mesh, dry at 100℃ for 1.5h, control the moisture content ≤5%, get the pretreated polymer matrix; P2. Preparation of conductive filler: select silver elemental particles with an average particle size of 100-300 nm and MXene with a sheet thickness of ≤5 nm and a lateral size of 1-5 μm, mix the two as an electronic type conductive filler for standby; P3. Preparation of crosslinking agent: mix polyethylene glycol diacrylate and borax until uniform, to obtain a crosslinking agent; P4. Preparation of mixed solvent: take water and dimethyl sulfoxide in a volume ratio of 1:2, mix thoroughly to prepare a water / dimethyl sulfoxide mixed solvent; P5. Preparation of composite modifier: take triphenyl phosphite, sodium tetraborate, and sodium silicate in a mass ratio of 3:4:6, mix and stir until uniform to obtain a composite modifier; P6. Preparation of epoxy-modified nano-SiO2 / silver particles: mix nano-SiO2 and silver nanoparticles in a mass ratio of 3:1, crush to 100-120 mesh to obtain a mixed powder; prepare a 2% KH-560 ethanol solution, and add the mixed powder and the ethanol solution in a mass ratio of 100:15 to a reaction kettle; control the temperature of the reaction kettle at 50°C and the stirring speed at 300 r / min, and stir for 30 min; after the reaction is completed, filter, wash the residue with anhydrous ethanol twice, and dry the residue in a 70°C vacuum oven for 2 h to obtain epoxy-modified nano-SiO2 / silver particles; P7. Preparation of modified MXene: disperse MXene sheets in deionized water, add 1% dopamine solution by mass fraction, and stir at 30°C for 6 h; then add 0.5% silane coupling agent KH-550 by mass fraction, and continue to stir for 2 h; centrifuge to obtain a solid product, wash with deionized water for 3 times, and dry the product in a 60°C vacuum drying oven for 4 h to obtain modified MXene; P8. Preparation of modified montmorillonite: take sodium-based montmorillonite and add 2% hydrochloric acid solution, mechanically stir at 50°C for 5 h, discard the supernatant after centrifugation, and wash the solid with deionized water until AgN titration is free of precipitate; dry the washed solid in a 60°C vacuum oven for 24 h, grind and pass through a 100 mesh sieve to obtain hydrochloric acid-activated montmorillonite; mix the hydrochloric acid-activated montmorillonite and cetyltrimethylammonium bromide in a mass ratio of 100:40, add deionized water, and mechanically stir at 65°C for 24 h; discard the supernatant after centrifugation, wash the solid with deionized water until no foam is generated, dry in a 60°C vacuum oven for 24 h, grind and pass through a 100 mesh sieve to obtain modified montmorillonite; P9. Preparation of dispersant: select polyvinylpyrrolidone as a dispersant; P10. Preparation of anti-aging agent: select hindered phenol BHT as an anti-aging agent; P11. Preparation of conductive filler dispersion liquid: the conductive filler (a mixture of silver elemental particles and MXene) in P2 is added to the polyvinylpyrrolidone in P9, and ultrasonic dispersion is performed for 15 min to form a uniform conductive filler dispersion liquid; P12. Preparation of composite filler: the epoxy modified nano-SiO2 / silver particles in P6, the modified MXene in P7, and the modified montmorillonite in P8 are mixed and stirred according to a mass ratio of 3.5:1.5:0.8 to obtain a composite filler; P13. Construction of functionalized system: the conductive filler dispersion liquid in P11 is added to a kneader, and the polymer matrix in P1 is added at the same time, followed by the water / dimethyl sulfoxide mixed solvent in P4, stirring until uniform, and then adding the composite modifier in P5; the temperature is controlled at 20℃, the rotation speed is 300r / min, and stirring is performed for 30 min; then the crosslinking agent in P3 is added, and the water content of the system is adjusted to 7%, to obtain a pre-crosslinked system; the pre-crosslinked system is heated to 40℃, the composite filler in P12 is added, and stirring is performed for 30 min; then the conductive filler dispersion liquid is added, and stirring is performed for 30 min at constant temperature, to obtain a functionalized system; P14. Molding and post-processing: the functionalized system in P13 is injected into a mold, and low-temperature 3D printing molding is performed according to the following parameters (the shear rate is 1s -1 -1 at 25℃, the viscosity is 1000mPa·s, the extrusion rate is 0.5mm / s, the inner diameter of the printing nozzle is 0.4mm, the printing platform temperature is -20℃, the printing layer number is 5, and the thickness of each layer is 0.2mm); after molding, freeze-thaw cycle crosslinking is performed (the freezing temperature is -20℃, the freezing time is 10h, the thawing temperature is room temperature, and the thawing time is 2h); after crosslinking, the product is soaked in deionized water for 4 days, and the water is changed every 12h; the hindered phenol BHT in P10 is added, and vacuum drying is performed at a segmented temperature control (the first stage is 78℃ for 3h, the second stage is 88℃ for 3h, and the vacuum degree is -0.09MPa) for 6h, to finally obtain a conductive hydrogel.

[0020] Example 2: A method for preparing a conductive hydrogel, comprising the following steps: P1. Preparation of polymer matrix: polyvinyl alcohol with a degree of polymerization of 1700-2000 and sodium carboxymethyl cellulose with a degree of substitution of 0.6-0.8 are mixed according to a mass ratio of 7:1, then pulverized to 80-100 mesh, and dried at 103℃ for 1.5h to control the water content to ≤5%, to obtain a pretreated polymer matrix; P2. Preparation of conductive filler: silver elemental particles with an average particle size of 100-300nm and MXene with a sheet thickness of ≤5nm and a lateral size of 1-5μm are mixed as electronic conductive filler for standby; P3. Preparation of crosslinking agent: polyethylene glycol diacrylate and borax are mixed and stirred until uniform to obtain a crosslinking agent; P4. Mixed solvent preparation: take water and dimethyl sulfoxide by volume ratio 1:2, mix well, and prepare water / dimethyl sulfoxide mixed solvent; P5. Composite modifier preparation: take triphenyl phosphite, sodium tetraborate, and sodium silicate by mass ratio 4:5:8, mix and stir well, and obtain composite modifier; P6. Preparation of epoxy modified nano-SiO2 / silver particles: mix nano-SiO2 and silver nanoparticles by mass ratio 3:1, crush to 100-120 mesh to obtain mixed powder; prepare a 2% KH-560 ethanol solution, and add the mixed powder and the ethanol solution by mass ratio 100:18 into a reaction kettle; control the temperature of the reaction kettle at 53℃ and the rotation speed at 330r / min, and stir for 33min; after the reaction is completed, filter, wash the residue with anhydrous ethanol for 2 times, and dry the residue in a vacuum oven at 73℃ for 2h to obtain epoxy modified nano-SiO2 / silver particles; P7. Preparation of modified MXene: disperse MXene sheets in deionized water, add 1% dopamine solution by mass fraction, and stir at 33℃ for 6h; then add 0.5% silane coupling agent KH-550 by mass fraction, and continue to stir for 2h; centrifugal separation to obtain solid product, wash with deionized water for 3 times, and dry the product in a vacuum drying oven at 63℃ for 4h to obtain modified MXene; P8. Preparation of modified montmorillonite: take sodium-based montmorillonite, add 2% hydrochloric acid solution, mechanically stir at 50℃ for 5h, discard the supernatant after centrifugation, and wash the solid with deionized water until AgN titration has no precipitation; dry the washed solid in a vacuum oven at 60℃ for 24h, grind and pass through a 100 mesh sieve to obtain hydrochloric acid activated montmorillonite; mix the hydrochloric acid activated montmorillonite with cetyltrimethylammonium bromide by mass ratio 100:40, add deionized water, and mechanically stir at 65℃ for 24h; discard the supernatant after centrifugation, wash the solid with deionized water until no foam is generated, dry in a vacuum oven at 60℃ for 24h, grind and pass through a 100 mesh sieve to obtain modified montmorillonite; P9. Preparation of dispersant: select polyvinylpyrrolidone as dispersant; P10. Preparation of anti-aging agent: select hindered phenol BHT as anti-aging agent; P11. Preparation of conductive filler dispersion liquid: add the conductive filler (silver single particle and MXene mixture) in P2 into the polyvinylpyrrolidone in P9, and ultrasonic dispersion for 16min to form a uniform conductive filler dispersion liquid; P12. Preparation of composite filler: take epoxy modified nano-SiO2 / silver particles in P6, modified MXene in P7, and modified montmorillonite in P8 by mass ratio 3.5:1.5:0.8, mix and stir well to obtain composite filler; P13. Functional system construction: add the conductive filler dispersion liquid of P11 into the kneader, add the polymer matrix of P1, then add the water / dimethyl sulfoxide mixed solvent of P4 and stir until uniform, then add the composite modifier of P5; control the temperature at 23℃ and the rotation speed at 330r / min, and stir for 40min; then add the crosslinking agent of P3 and adjust the water content of the system to 9%, to obtain a pre-crosslinking system; heat the pre-crosslinking system to 43℃, add the composite filler of P12 and stir for 33min; then add the conductive filler dispersion liquid and keep stirring for 38min to obtain a functional system; P14. Molding and post-processing: inject the functional system of P13 into a mold and perform low-temperature 3D printing molding (shear rate 4s -1 viscosity 1000mPa·s, extrusion rate 0.8mm / s, printing nozzle inner diameter 0.5mm, printing platform temperature -20℃, printing layer number 6, and each layer thickness 0.2mm) according to the following parameters; after molding, perform freeze-thaw cycle crosslinking (freezing temperature -20℃, freezing time 10h, thawing temperature room temperature, and thawing time 2h); after crosslinking, soak in deionized water for 4 days, and change the water every 12h; add the hindered phenol BHT of P10 and perform vacuum drying for 8h according to the segmented temperature control (first stage 78℃ for 3h, second stage 88℃ for 4h, and vacuum degree -0.09MPa) to finally obtain a conductive hydrogel.

[0021] Example 3: A method for preparing a conductive hydrogel, comprising the following steps: P1. Polymer matrix preparation: mix polyvinyl alcohol with a degree of polymerization of 1700-2000 and sodium carboxymethyl cellulose with a degree of substitution of 0.6-0.8 according to a mass ratio of 8:1, crush to 80-100 mesh, and dry in an environment of 106℃ for 2h to control the water content to ≤5%, to obtain a pretreated polymer matrix; P2. Conductive filler preparation: select silver single-element particles with an average particle size of 100-300nm and MXene with a sheet thickness of ≤5nm and a lateral size of 1-5μm, mix them as an electronic conductive filler for standby; P3. Crosslinking agent preparation: mix polyethylene glycol diacrylate and borax and stir until uniform to obtain a crosslinking agent; P4. Mixed solvent preparation: take water and dimethyl sulfoxide according to a volume ratio of 1:3, and mix them thoroughly to prepare a water / dimethyl sulfoxide mixed solvent; P5. Composite modifier preparation: take triphenyl phosphite, sodium tetraborate, and sodium silicate according to a mass ratio of 6:6:10, mix them, and stir until uniform to obtain a composite modifier; P6. Preparation of epoxy-modified nano-SiO2 / silver particles: Mix nano-SiO2 and silver nanoparticles at a mass ratio of 4:1, crush to 100-120 mesh to obtain a mixed powder; prepare a 3% mass fraction KH-560 ethanol solution, and add the mixed powder and the ethanol solution at a mass ratio of 100:21 into a reaction kettle; control the temperature of the reaction kettle at 56°C and the rotation speed at 360 r / min, and stir for 36 min; after the reaction is completed, filter, wash the filter residue with anhydrous ethanol for 3 times, and dry the filter residue in a vacuum oven at 76°C for 3 h to obtain epoxy-modified nano-SiO2 / silver particles; P7. Preparation of modified MXene: Disperse MXene sheets in deionized water, add a 2% mass fraction dopamine solution, and stir at 36°C for 7 h; then add a 1% mass fraction silane coupling agent KH-550, and continue to stir for 3 h; centrifugal separation to obtain a solid product, wash with deionized water for 4 times, and dry the product in a vacuum drying oven at 66°C for 5 h to obtain modified MXene; P8. Preparation of modified montmorillonite: Take sodium-based montmorillonite, add 2% hydrochloric acid solution, mechanically stir at 50°C for 5 h, discard the supernatant after centrifugation, and wash the solid with deionized water until the AgN titration is free of precipitate; dry the washed solid in a vacuum oven at 60°C for 24 h, grind and pass through a 100 mesh sieve to obtain hydrochloric acid activated montmorillonite; mix the hydrochloric acid activated montmorillonite with cetyltrimethylammonium bromide at a mass ratio of 100:40, add deionized water, and mechanically stir at 65°C for 24 h; discard the supernatant after centrifugation, wash the solid with deionized water until there is no foam, dry in a vacuum oven at 60°C for 24 h, grind and pass through a 100 mesh sieve to obtain modified montmorillonite; P9. Preparation of dispersant: Select polyvinylpyrrolidone as the dispersant; P10. Preparation of anti-aging agent: Select hindered phenol BHT as the anti-aging agent; P11. Preparation of conductive filler dispersion liquid: Add the conductive filler (a mixture of silver single particles and MXene) in P2 into the polyvinylpyrrolidone in P9, and ultrasonic disperse for 18 min to form a uniform conductive filler dispersion liquid; P12. Preparation of composite filler: Take the epoxy-modified nano-SiO2 / silver particles in P6, the modified MXene in P7, and the modified montmorillonite in P8 at a mass ratio of 4:2:1, mix and stir until uniform to obtain a composite filler; P13. Functional system construction: add the conductive filler dispersion liquid of P11 into the kneader, add the polymer matrix of P1, then add the water / dimethyl sulfoxide mixed solvent of P4 and stir until uniform, then add the composite modifier of P5; control the temperature at 26℃ and the rotation speed at 360r / min, and stir for 50min; then add the crosslinking agent of P3 and adjust the water content of the system to 11%, to obtain a pre-crosslinking system; heat the pre-crosslinking system to 46℃, add the composite filler of P12, and stir for 36min; then add the conductive filler dispersion liquid and keep stirring at 46min, to obtain a functional system; P14. Molding and post-processing: inject the functional system of P13 into a mold, and perform low-temperature 3D printing molding according to the following parameters (viscosity 2000mPa·s at a shear rate of 8s -1 at 25℃, extrusion rate 1mm / s, printing nozzle inner diameter 0.7mm, printing platform temperature -15℃, printing layer number 8, and each layer thickness 0.3mm); after molding, perform freeze-thaw cycle crosslinking (freezing temperature -18℃, freezing time 11h, thawing temperature room temperature, and thawing time 3h); after crosslinking, soak in deionized water for 5 days, and change the water every 12h; add the hindered phenol BHT of P10, and perform vacuum drying for 9h according to the segmented temperature control (first stage 80℃ for 4h, second stage 90℃ for 5h, and vacuum degree -0.07MPa), to finally obtain a conductive hydrogel.

[0022] Example 4: A method for preparing a conductive hydrogel, comprising the following steps: P1. Polymer matrix preparation: mix polyvinyl alcohol with a polymerization degree of 1700-2000 and sodium carboxymethyl cellulose with a substitution degree of 0.6-0.8 according to a mass ratio of 9:1, crush to 80-100 mesh, and dry at 110℃ for 2.5h to control the water content to ≤5%, to obtain a pretreated polymer matrix; P2. Conductive filler preparation: select silver single-element particles with an average particle size of 100-300nm and MXene with a sheet thickness of ≤5nm and a lateral size of 1-5μm, mix them as an electronic conductive filler for standby; P3. Crosslinking agent preparation: mix polyethylene glycol diacrylate and borax and stir until uniform, to obtain a crosslinking agent; P4. Mixed solvent preparation: take water and dimethyl sulfoxide according to a volume ratio of 1:3, and mix them thoroughly to prepare a water / dimethyl sulfoxide mixed solvent; P5. Composite modifier preparation: take triphenyl phosphite, sodium tetraborate, and sodium silicate according to a mass ratio of 8:8:12, mix them, and stir until uniform, to obtain a composite modifier; P6. Preparation of epoxy-modified nano-SiO2 / silver particles: Mix nano-SiO2 and silver nanoparticles at a mass ratio of 5:1, crush to 100-120 mesh to obtain a mixed powder; prepare a 4% mass fraction KH-560 ethanol solution, and add the mixed powder and the ethanol solution at a mass ratio of 100:25 into a reaction kettle; control the temperature of the reaction kettle at 60°C and the rotation speed at 400 r / min, and stir for 40 min; after the reaction is completed, filter, wash the filter residue with anhydrous ethanol for 3 times, and dry the filter residue in a vacuum oven at 80°C for 3 h to obtain epoxy-modified nano-SiO2 / silver particles; P7. Preparation of modified MXene: Disperse MXene sheets in deionized water, add a 3% mass fraction of dopamine solution, and stir at 40°C for 8 h; then add a 1.5% mass fraction of silane coupling agent KH-550, and continue to stir for 3 h; centrifugal separation to obtain a solid product, wash with deionized water for 4 times, and dry the product in a vacuum drying oven at 70°C for 5 h to obtain modified MXene; P8. Preparation of modified montmorillonite: Take sodium-based montmorillonite and add 2% hydrochloric acid solution, mechanically stir at 50°C for 5 h, discard the supernatant after centrifugation, and wash the solid with deionized water until AgN titration has no precipitate; dry the washed solid in a vacuum oven at 60°C for 24 h, grind and pass through a 100 mesh sieve to obtain hydrochloric acid activated montmorillonite; mix the hydrochloric acid activated montmorillonite with cetyltrimethylammonium bromide at a mass ratio of 100:40, add deionized water, and mechanically stir at 65°C for 24 h; discard the supernatant after centrifugation, wash the solid with deionized water until no foam is generated, dry in a vacuum oven at 60°C for 24 h, grind and pass through a 100 mesh sieve to obtain modified montmorillonite; P9. Preparation of dispersant: Select polyvinylpyrrolidone as a dispersant; P10. Preparation of anti-aging agent: Select hindered phenol BHT as an anti-aging agent; P11. Preparation of conductive filler dispersion liquid: Add the conductive filler (a mixture of silver single particles and MXene) in P2 to the polyvinylpyrrolidone in P9, and ultrasonic disperse for 20 min to form a uniform conductive filler dispersion liquid; P12. Preparation of composite filler: Take the epoxy-modified nano-SiO2 / silver particles in P6, the modified MXene in P7, and the modified montmorillonite in P8 at a mass ratio of 4.5:2.5:1.2, mix and stir until uniform to obtain a composite filler; P13. Functional system construction: add the conductive filler dispersion liquid of P11 into the kneader, add the polymer matrix of P1, then add the water / dimethyl sulfoxide mixed solvent of P4 and stir until uniform, then add the composite modifier of P5; control the temperature at 30℃, the rotation speed at 400r / min, and stir for 60min; then add the crosslinking agent of P3 and adjust the water content of the system to 12%, to obtain a pre-crosslinking system; heat the pre-crosslinking system to 50℃, add the composite filler of P12, and stir for 40min; then add the conductive filler dispersion liquid and stir for 50min at constant temperature, to obtain a functional system; P14. Molding and post-processing: inject the functional system of P13 into a mold, and perform low-temperature 3D printing molding according to the following parameters (viscosity 3000mPa·s at a shear rate of 10s -1 time 12h, thawing temperature room temperature, and thawing time 4h); after crosslinking, soak in deionized water for 6 days, and change the water every 12h; add the hindered phenol BHT of P10, and perform vacuum drying for 10h according to the segmented temperature control (82℃ for the first stage, 4h; 92℃ for the second stage, 6h; vacuum degree -0.07MPa), to finally obtain a conductive hydrogel.

[0023] Comparative Example 1: This comparative example is compared with Example 1 only by replacing “polyvinyl alcohol with a degree of polymerization of 1700-2000 and sodium carboxymethyl cellulose with a degree of substitution of 0.6-0.8 mixed at a mass ratio of 6:1” with “single polyvinyl alcohol with a degree of polymerization of 1700-2000”, and the rest of the steps and parameters are the same. This comparative example will not be repeated here. Finally, a conductive hydrogel is obtained.

[0024] Comparative Example 2: This comparative example is compared with Example 1 only by replacing “silver single-element particles with an average particle size of 100-300nm and MXene with a sheet thickness of ≤5nm and a lateral size of 1-5μm mixed” with “single silver single-element particles with an average particle size of 100-300nm”, and the rest of the steps and parameters are the same. This comparative example will not be repeated here. Finally, a conductive hydrogel is obtained.

[0025] Comparative Example 3: This comparative example is compared with Example 1 only by not adding the composite modifier of triphenyl phosphite, sodium tetraborate and sodium silicate mixed at a mass ratio of 3:4:6, and the rest of the steps and parameters are the same. This comparative example will not be repeated here. Finally, a conductive hydrogel is obtained.

[0026] Comparative Example 4: The comparative example is compared with example 1 only by replacing "epoxy modified nano SiO2 / silver particles" with "unmodified nano SiO2 and silver nanoparticle mixture (mixed at a mass ratio of 3:1)", and the rest of the steps and parameters are the same. The comparative example will not be repeated here. The final conductive hydrogel is obtained.

[0027] Comparative example 5: The comparative example is compared with example 1 only by replacing "low-temperature 3D printing" with "conventional casting (pouring the functional system into the mold and curing at room temperature)", and the rest of the steps and parameters are the same. The comparative example will not be repeated here. The final conductive hydrogel is obtained.

[0028] Comparative example 6: The comparative example is compared with example 1 only by replacing "freeze-thaw cycle crosslinking" with "freeze-thaw cycle crosslinking", and the rest of the steps and parameters are the same. The comparative example will not be repeated here. The final conductive hydrogel is obtained.

[0029] Comparative example 7: The comparative example is compared with example 1 only by replacing "segmented temperature control vacuum drying (first stage 78°C for 3h, second stage 88°C for 3h)" with "single temperature vacuum drying (85°C directly for 6h)", and the rest of the steps and parameters are the same. The comparative example will not be repeated here. The final conductive hydrogel is obtained.

[0030] Comparative example 8: The comparative example is compared with example 1 only by replacing "the mass ratio of epoxy modified nano SiO2 / silver particles, modified MXene, and modified montmorillonite in the composite filler is 3.5:1.5:0.8" with "the mass ratio of epoxy modified nano SiO2 / silver particles, modified MXene, and modified montmorillonite in the composite filler is 1:1:1", and the rest of the steps and parameters are the same. The comparative example will not be repeated here. The final conductive hydrogel is obtained.

[0031] Performance test: Test method: Conductivity: Four-probe tester was used to test the surface conductivity of the sample at room temperature; Tensile strength and elongation at break: The tensile rate was 5mm / min, and the sample size was 10mm×2mm×1mm; Anti-aging performance: The sample was placed in an oven at 80°C for 500h, and the average retention rate of conductivity and tensile strength after aging was tested; Molding precision deviation rate: Laser range finder was used to measure the deviation rate (average value) between the actual size and the designed size of the printed sample; Water content change rate: The sample was placed in a 25°C, 50% humidity environment for 30 days, and the water content change rate was tested; Mechanical cycle stability: test the tensile strength retention rate after 100 times of stretching-recovery cycles (stretching to 50% of the breaking elongation).

[0032] The test results are shown in Tables 1-3 below: Table 1 Performance test results of Examples 1-4

[0033] Table 2 Performance test results of Comparative Examples 1-4

[0034] Table 3 Performance test results of Comparative Examples 5-8

[0035] Data analysis: As can be seen from the test results in Table 1, the conductive hydrogel prepared by the present application (Examples 1-4) exhibits excellent and synergistic comprehensive performance in terms of electrical conductivity, mechanical properties, anti-aging performance, molding precision and stability, etc., fully meeting the use requirements of flexible sensors, electronic skin, wearable flexible electronic devices and other scenarios.

[0036] Examples 1-4: electrical conductivity ≥1.2 S / m (up to 1.8 S / m), tensile strength ≥2.0 MPa (up to 2.6 MPa), breaking elongation ≥300% (up to 360%), anti-aging performance retention rate ≥80% (up to 88%), molding precision deviation rate ≤±5.0% (lowest ±2.5%), water content change rate ≤10.0% (lowest 7.8%), mechanical cycle stability retention rate ≥85% (up to 90%), and each performance gradually improves with the optimization of raw material ratio and process parameters.

[0037] Comparative Example 1, due to not using a polyvinyl alcohol-sodium carboxymethyl cellulose composite matrix, but only using a single polyvinyl alcohol, resulting in insufficient mechanical support and decreased water absorption stability of the material, the tensile strength decreased to 1.3 MPa, the breaking elongation was only 210%, the water content change rate increased to 16.5%, and the electrical conductivity decreased to 0.9 S / m due to weakened compatibility between the matrix and the filler; Comparative Example 2, due to only using a single silver particle as a conductive filler, lacking a continuous conductive path constructed by MXene layers, the electrical conductivity decreased to 0.8 S / m, the anti-aging performance retention rate was only 70%, and the mechanical cycle stability also decreased to 74% due to incomplete conductive network; Comparative Example 3: The interface between the filler and the matrix was severely agglomerated due to the absence of composite modifier, with an electrical conductivity of only 0.7 S / m (the lowest value among all the examples), a tensile strength of 1.2 MPa, an anti-aging performance retention rate of 65%, and a water content change rate of 18.8%, all of which were the worst among all the tested samples; Comparative Example 4: The tensile strength was reduced to 1.4 MPa, the elongation at break was 220%, the anti-aging performance retention rate was 68%, and the electrical conductivity was reduced to 0.8 S / m due to the weak interfacial bonding between the unmodified nano-SiO2 / silver particles and the polymer matrix, and the uneven dispersion of the filler; Comparative Example 5: The molding precision deviation rate increased to ±12.0% due to the replacement of conventional casting molding, which lacked the precise shape control effect of low-temperature 3D printing. The tensile strength was 1.6 MPa, and the mechanical cycle stability retention rate was 78%, both of which were lower than those of Example 1. Comparative Example 6: The tensile strength was 1.5 MPa, the elongation at break was 240%, the anti-aging performance retention rate was 73%, and the water content change rate was 13.8% due to the omission of the freeze-thaw cycle crosslinking, which resulted in insufficient crosslinking density of the polymer network. This demonstrated the key strengthening effect of this process on network stability. Comparative Example 7: The tensile strength was 1.7 MPa (lower than 2.0 MPa of Example 1), the mechanical cycle stability retention rate was 76% (lower than 85% of Example 1), and the water content change rate was 12.5% (higher than 10.0% of Example 1) due to the replacement of "segmented temperature-controlled vacuum drying" with "single 85°C vacuum drying for 6 hours", which resulted in the rapid evaporation of water on the surface of the material to form a hard shell, hindering the diffusion of internal bound water, and thus producing internal micro-cracks. This proved the necessity of segmented temperature control for ensuring the stability of the hydrogel structure and performance.

[0038] Comparative Example 8: The composite filler ratio was changed to 1:1:1, which broke the synergistic mechanism of "epoxy-modified nano-SiO2 / silver particles (conductive nodes) - modified MXene (conductive paths) - modified montmorillonite (network stability)": the high proportion of modified montmorillonite agglomerated and interfered with the conductive paths, and the low proportion of epoxy-modified nano-SiO2 / silver particles resulted in the absence of conductive nodes. The electrical conductivity was 0.9 S / m (lower than 1.2 S / m of Example 1), and the tensile strength was 1.6 MPa (lower than 2.0 MPa of Example 1), which verified the optimization value of the original composite filler ratio.

[0039] It should be understood by those of ordinary skill in the art that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest that the scope of the present application is limited to these examples; under the concept of the present application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the present application as described above. In order to be brief, they are not provided in detail.

[0040] The present application is intended to cover all such alternatives, modifications, and variations as fall within the broad scope of the appended claims. Accordingly, any and all such alternatives, modifications, equivalents, improvements and the like are intended to be encompassed by the present application.

Claims

1. A conductive hydrogel, characterized in that, It is prepared from the following raw materials in parts by weight: 40-70 parts polymer matrix, 5-20 parts conductive filler, 1-5 parts crosslinking agent, 80-150 parts mixed solvent, 8-25 parts composite modifier, 2-8 parts composite filler, 2-6 parts dispersant, and 0.3-1.0 parts anti-aging agent; The mixed solvent is a water / dimethyl sulfoxide mixed solvent, wherein the volume ratio of water to dimethyl sulfoxide in the water / dimethyl sulfoxide mixed solvent is 1:2-3; The composite modifier is prepared by triphenyl phosphite, sodium tetraborate and sodium silicate in a mass ratio of 3-8:4-8:6-12. The composite filler was prepared by epoxy-modified nano-SiO2 / silver particles, modified MXene, and modified montmorillonite in a mass ratio of 3.5-4.5:1.5-2.5:0.8-1.

2.

2. The conductive hydrogel according to claim 1, characterized in that, The polymer matrix is ​​a composite system of polyvinyl alcohol and sodium carboxymethyl cellulose; the degree of polymerization of the polyvinyl alcohol is 1700-2000, the degree of substitution of the sodium carboxymethyl cellulose is 0.6-0.8, and the mass ratio of polyvinyl alcohol to sodium carboxymethyl cellulose in the composite system is 6-9:

1.

3. The conductive hydrogel according to claim 1, characterized in that, The conductive filler is an electronic conductive filler; the electronic conductive filler is a mixture of silver elemental particles and MXene; the average particle size of the silver elemental particles is 100-300nm, and the thickness of the MXene sheets is ≤5nm and the lateral dimension is 1-5μm.

4. The conductive hydrogel according to claim 1, characterized in that, The crosslinking agent is a mixture of polyethylene glycol diacrylate and borax; the dispersant is polyvinylpyrrolidone; and the anti-aging agent is hindered phenol BHT.

5. The conductive hydrogel according to claim 1, characterized in that, The preparation method of the epoxy-modified nano-SiO2 / silver particles is as follows: Step A1. Mix nano-SiO2 and silver nanoparticles at a mass ratio of 3-5:1, and pulverize to 100-120 mesh to obtain a mixed powder; Step A2. Prepare a 2%-4% KH-560 ethanol solution by mixing the mixed powder with the KH-560 ethanol solution at a mass ratio of 100:15-25 and adding it to the reaction vessel; Step A3. Control the reactor temperature to 50-60℃, the rotation speed to 300-400 r / min, and stir for 30-40 min; Step A4. After the reaction is complete, filter the mixture, wash it 2-3 times with anhydrous ethanol, and dry it in a vacuum oven at 70-80℃ for 2-3 hours to obtain epoxy-modified nano-SiO2 / silver particles.

6. The conductive hydrogel according to claim 1, characterized in that, The modified MXene is prepared as follows: Step B1. Disperse MXene sheets in deionized water, add 1%-3% (w / w) dopamine solution, and stir at 30-40℃ for 6-8 hours; Step B2. Add 0.5%-1.5% by mass of silane coupling agent KH-550 and continue stirring for 2-3 hours; Step B3. Centrifuge, wash with deionized water 3-4 times, and vacuum dry at 60-70℃ for 4-5 hours to obtain modified MXene.

7. The conductive hydrogel according to claim 1, characterized in that, The modified montmorillonite is prepared as follows: Step C1. Add sodium montmorillonite to a 2% hydrochloric acid solution, mechanically stir at 50°C for 5 hours, centrifuge and discard the supernatant, then wash with water until AgN is reached. No precipitate was obtained by titration, and the mixture was dried under vacuum at 60℃ for 24 hours. After grinding and passing through a 100-mesh sieve, hydrochloric acid-activated montmorillonite was obtained. Step C2. Mix hydrochloric acid-activated montmorillonite with hexadecyltrimethylammonium bromide at a mass ratio of 100:40, add deionized water, mechanically stir at 65°C for 24 hours, centrifuge and discard the supernatant, wash with water until no foam is present, vacuum dry at 60°C for 24 hours, grind through a 100-mesh sieve to obtain modified montmorillonite.

8. The method for preparing the conductive hydrogel according to any one of claims 1-7, characterized in that, Includes the following steps: Step S1. Raw material pretreatment: The polymer matrix is ​​pulverized to 80-100 mesh and dried at 100-110℃ for 1.5-2.5h, with the moisture content controlled at ≤5%; the conductive filler and dispersant are mixed and ultrasonically dispersed for 15-20min to form a uniform dispersion. Step S2. Construction of pre-crosslinked system: Add the uniformly dispersed liquid to the kneader, add the mixed solvent, stir evenly, add the composite modifier, control the temperature at 20-30℃ and the speed at 300-400r / min, stir for 30-60min, then add the crosslinking agent, adjust the water content of the system to 7%-12%, and obtain the pre-crosslinked system; Step S3. Composite reinforcement and conductive functionalization: Add composite filler to the pre-crosslinked system, heat to 40-50℃, stir for 30-40 min, add electronic conductive filler dispersion, keep warm and stir for 30-50 min to obtain functionalized system; Step S4. Molding and Post-processing: The functionalized system is injected into the mold and shaped by low-temperature 3D printing. It is then cross-linked by freeze-thaw cycle, with freezing temperature of -18 to -20℃ and freezing time of 10 to 12 hours, and thawing temperature of room temperature and thawing time of 2 to 4 hours. After molding, it is soaked in deionized water for 4 to 6 days, with the water changed every 12 hours. An anti-aging agent is added, and it is vacuum dried at 80 to 90℃ and vacuum degree of -0.09 to -0.07 MPa for 6 to 10 hours to obtain conductive hydrogel.

9. The method for preparing the conductive hydrogel according to claim 8, characterized in that, During the low-temperature 3D printing process described in step S4, the rheological properties of the printing ink satisfy the following: shear rate of 1-10 s at 25°C. -1 It has a viscosity of 1000-3000 mPa·s and shear-thinning properties; the printing parameters are: extrusion rate 0.5-1.2 mm / s, print nozzle inner diameter 0.4-0.8 mm, printing platform temperature -20--15℃, number of printing layers 5-10, and thickness of each layer 0.2-0.4 mm.

10. The method for preparing the conductive hydrogel according to claim 8, characterized in that, The vacuum drying described in step S4 uses segmented temperature control: the first stage is maintained at 78-82℃ for 3-4 hours to remove surface moisture, and the second stage is maintained at 88-92℃ for 3-6 hours to remove bound water.

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