Conductive hydrogel and its preparation method and application

Abstract

The present invention discloses a conductive hydrogel and a preparation method and application thereof. The preparation method comprises: mixing polyvinyl alcohol, a moisture humectant and water and stirring to obtain a first mixed solution; mixing a polymerized monomer, a cross-linking agent, a photoinitiator, and a water-soluble inorganic salt with the first mixed solution and stirring to obtain a second mixed solution; subjecting the second mixed solution to ultraviolet cross-linking film-forming treatment to obtain a precursor film; subjecting the precursor film to freezing treatment, keeping one side of the precursor film in a room temperature environment and the other side in a low temperature environment, so that the freezing of the precursor film is carried out from the low temperature side to the room temperature side, and a conductive hydrogel is obtained. The method can not only realize the differentiation of longitudinal and transverse conductivity of the conductive hydrogel, but also the strength of the conductive hydrogel obtained is very good, and no additional non-woven fabric or other materials are required to increase the strength. When it is used in a massager, the installation problem can be solved at one time, which is not only convenient and fast, but also more comfortable to experience.

Description

Technical Field

[0001] The invention belongs to the field of materials, and in particular relates to a conductive hydrogel and a preparation method and application thereof. Background Art

[0002] Traditional conductive hydrogels mainly use water and certain inorganic salts to achieve conductive functionality. They are homogeneous materials with little difference in transverse and longitudinal conductivity and weak conductivity. However, when using conductive hydrogels on massagers, people hope that the conductivity of the hydrogels in the direction of use of the massager will be more significant, with differentiated conductivity in all directions, so as to produce a more comfortable experience. In addition, most traditional hydrogel materials are mainly composed of polyacrylamide, which has poor mechanical properties, low strength, and inconvenient operation during use. Therefore, the performance of conductive hydrogels still needs to be further improved. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one object of the present invention is to provide a conductive hydrogel and a preparation method and application thereof. The preparation method can not only achieve the differentiation of longitudinal and transverse conductivity of the conductive hydrogel, but also the strength of the conductive hydrogel is very good, and no additional non-woven fabric or other materials are required to increase the strength. When it is used in a massager, the installation problem can be solved at one time, which is not only convenient and fast, but also more comfortable to experience.

[0004] This application is mainly based on the following issues:

[0005] The hydrogels currently available on the market are homogeneous, that is, the conductivity in the horizontal and vertical directions is consistent, and it is impossible to obtain more significant conductivity in the direction of use of the massager; and the material strength is poor. When used on a four-electrode massage head, a skeleton is required to support it (such as non-woven fabric) or increase the strength, or it needs to be disassembled piece by piece during use, which is very inconvenient to operate.

[0006] To this end, according to a first aspect of the present invention, the present invention provides a method for preparing a conductive hydrogel. According to an embodiment of the present invention, the method comprises:

[0007] (1) mixing polyvinyl alcohol, a moisture humectant and water and stirring to obtain a first mixed solution;

[0008] (2) mixing a polymerizable monomer, a cross-linking agent, a photoinitiator, and a water-soluble inorganic salt with the first mixed solution and stirring to obtain a second mixed solution;

[0009] (3) performing ultraviolet cross-linking film-forming treatment on the second mixed solution to obtain a precursor film;

[0010] (4) The precursor film is subjected to a freezing treatment, during which one side of the precursor film is kept at room temperature and the other side is kept at a low temperature, so that the freezing of the precursor film is carried out from the low temperature side to the room temperature side, so as to obtain a conductive hydrogel.

[0011] According to the method for preparing conductive hydrogel in the above embodiment of the present invention, on the one hand, polyvinyl alcohol and polymerized monomers are compounded as film-forming materials in the formula system, and the network structure formed by the cross-linking polymerization of polyvinyl alcohol and the network structure formed by the cross-linking polymerization of the polymerized monomers are intertwined to form a double three-dimensional network structure, which gives the hydrogel material efficient water retention and excellent mechanical properties, and no additional skeleton support is required to make up for the strength of the hydrogel material itself; on the other hand, the temperature difference freezing process is used to make the internal structure of the hydrogel undergo a significant orientation change, and the direction of the conductive ions can be arranged in a specific manner according to a predetermined direction, thereby improving the conductivity and sensing sensitivity. Compared with the current situation that the existing hydrogel is homogeneously conductive, that is, the lateral and longitudinal conductivity are consistent, the conductive hydrogel prepared in the present invention has strong longitudinal conductivity and poor lateral conductivity, which can better realize the differentiation of the conductive direction. Using it in a massage device can produce a more comfortable experience strength, and solves the current situation that the existing conductive hydrogel cannot be partitioned into a single piece to achieve a multi-electrode EMS massage effect. Therefore, this method can not only achieve the differentiation of longitudinal and transverse conductivity of conductive hydrogels, but also the produced conductive hydrogel has very good strength and does not require additional non-woven fabrics or other materials to increase the strength. When it is used in a massager, the installation problem can be solved at one time. It is not only convenient and fast, but also the experience of strength is more comfortable.

[0012] In addition, the method for preparing a conductive hydrogel according to the above embodiment of the present invention may also have the following additional technical features:

[0013] In some embodiments of the present invention, in step (1), the moisture humectant includes at least one of glycerol, methyl propanediol, 1,3-propylene glycol and 1,2-hexanediol.

[0014] In some embodiments of the present invention, in step (1), the water includes at least one of ultrapure water, distilled water and deionized water.

[0015] In some embodiments of the present invention, in step (1), the mixing temperature is 80-100° C., and the stirring time is 0.5-3 h.

[0016] In some embodiments of the present invention, in step (1), 2 to 5 parts by weight of the moisture-keeping agent and 5 to 8 parts by weight of the water are mixed in advance to obtain a moisture-keeping agent aqueous solution; and then 0.5 to 2 parts by weight of the polyvinyl alcohol are mixed with the moisture-keeping agent aqueous solution.

[0017] In some embodiments of the present invention, in step (2), the polymerization monomer includes at least one of acrylamide, sodium acrylate and chitosan.

[0018] In some embodiments of the present invention, in step (2), the cross-linking agent includes at least one of polyamides, aliphatic amines, aromatic amines, and polyether amines.

[0019] In some embodiments of the present invention, in step (2), the photoinitiator includes at least one of brands 2959, 1173, 907 and 184.

[0020] In some embodiments of the present invention, in step (2), the water-soluble inorganic salt includes sodium chloride and / or lithium chloride.

[0021] In some embodiments of the present invention, in step (2), the stirring time is 30 to 50 minutes.

[0022] In some embodiments of the present invention, in step (2), the polymerization monomer is sodium acrylate and / or chitosan, and the water-soluble inorganic salt is lithium chloride.

[0023] In some embodiments of the present invention, in step (2), based on 0.5 to 2 parts by weight of the polyvinyl alcohol, 0.5 to 2 parts by weight of the polymerizable monomer, 0.015 to 0.025 parts by weight of the cross-linking agent, 0.005 to 0.02 parts by weight of the photoinitiator, and 0.5 to 2 parts by weight of the inorganic salt are dispersed in the first mixed solution in sequence, wherein the mass ratio of the polyvinyl alcohol to the polymerizable monomer is (0.6 to 2.4):1.

[0024] In some embodiments of the present invention, step (2) further comprises: adding a functional additive to the second mixed liquid, wherein the functional additive comprises at least one of a fragrance, a cooling agent and a skin conditioner.

[0025] In some embodiments of the present invention, the fragrance includes at least one of essence, balsam, essential oil and plant extract.

[0026] In some embodiments of the present invention, the functional additive includes at least one of mint flavor, menthol and menthol.

[0027] In some embodiments of the present invention, step (3) further includes: (3-1) using the heat conductive plate as the bottom plate and using a fixed plate to define a hydrogel forming area; (3-2) transferring the second mixed liquid to the hydrogel forming area and covering it with a transparent cover plate; (3-3) fixing the heat conductive plate and the transparent cover plate; (3-4) subjecting the second mixed liquid to ultraviolet irradiation through the transparent cover plate so that the second mixed liquid is cross-linked to form a film to obtain a precursor film.

[0028] In some embodiments of the present invention, a conductive hydrogel with a desired thickness and shape is obtained by controlling the height and shape of the hydrogel forming area.

[0029] In some embodiments of the present invention, the height of the fixing plate located on the thermally conductive plate is the same as the thickness of the conductive hydrogel.

[0030] In some embodiments of the present invention, in step (3), the height of the fixing plate is 0.6-1.2 mm, the ultraviolet cross-linking film-forming treatment is achieved by ultraviolet lamp irradiation, the ultraviolet cross-linking time is 0.5-2 min, and the ultraviolet lamp power is 0.1-4 KW.

[0031] In some embodiments of the present invention, the fixing plate is a silicone template, and the transparent cover plate is a glass plate.

[0032] In some embodiments of the present invention, the heat conducting plate and the transparent cover plate are fixed by using a fixing clamp or a counterweight.

[0033] In some embodiments of the present invention, step (4) includes: based on the product obtained in steps (3-4), keeping one side of the transparent cover plate at room temperature, and freezing the precursor film using liquid nitrogen through the heat conducting plate.

[0034] In some embodiments of the present invention, in step (4), the thickness of the precursor film is 0.6 to 1.2 mm, the temperature of the freezing treatment is -80 to -200° C., and the time is 3 to 10 min.

[0035] In some embodiments of the present invention, the freezing treatment is performed at a temperature of -150 to -200°C for 5 to 8 minutes.

[0036] In some embodiments of the present invention, the freezing treatment is carried out at a temperature of -196°C and for a time of 6 minutes.

[0037] In some embodiments of the present invention, in step (4), the device for performing the freezing treatment includes: a freezer and a cold source storage tank, the freezer includes a freezing tank, the freezing tank is suitable for accommodating a cold source, a cold source port is provided at the lower portion of the freezing tank, a support structure is formed at the upper portion of the freezing tank, the support structure is suitable for supporting a conductive hydrogel or a heat conductive plate and closing the freezing tank in combination with the conductive hydrogel or the heat conductive plate; the cold source storage tank is connected to the cold source port via a pipeline, and a cold source flow control valve is provided on the pipeline.

[0038] Based on the same inventive concept, according to the second aspect of the present invention, the present invention provides a conductive hydrogel. According to an embodiment of the present invention, the conductive hydrogel comprises: polyvinyl alcohol, a polymerizable monomer, a crosslinking agent, a photoinitiator, a water-soluble inorganic salt, a moisture humectant and water, the conductive hydrogel has a microscopic porous structure in thickness orientation, and the conductive hydrogel has different conductivity in its surface orientation and thickness orientation. Compared with the prior art, the hydrogel material uses polyvinyl alcohol as the main component. Polyvinyl alcohol is not only an extremely safe macromolecular organic substance, non-toxic to the human body, has no side effects, and has good biocompatibility, but also a double three-dimensional network structure formed by the intertwining of the network structure formed by the cross-linking polymerization of polyvinyl alcohol and the network structure formed by the cross-linking polymerization of the polymerized monomer, which gives the hydrogel material efficient water retention and excellent mechanical properties. No additional skeleton support (such as non-woven fabric or other materials) is required to make up for the strength of the hydrogel material itself, and it is more suitable for use in massagers. When it is used in massagers, the installation problem can be solved at one time, which is convenient and quick; further, the conductive hydrogel has a microscopic porous structure oriented perpendicular to the surface, which can form a directional conductive channel, so that the conductivity of the conductive hydrogel in its thickness orientation is significantly higher than its conductivity in the surface orientation, and using it in a massager can produce a more comfortable experience; in addition, the conductive hydrogel also has a certain viscosity and can adhere to a variety of substrates, such as metal, plastic, skin and other surfaces to form stable and reversible adhesion.

[0039] In some embodiments of the present invention, the conductive hydrogel includes: 2 to 5 parts by weight of the moisture retaining agent, 5 to 8 parts by weight of the water, 0.5 to 2 parts by weight of the polyvinyl alcohol, 0.5 to 2 parts by weight of the polymerized monomer, 0.015 to 0.025 parts by weight of the cross-linking agent, 0.005 to 0.02 parts by weight of the photoinitiator, and 0.5 to 2 parts by weight of the inorganic salt, and the mass ratio of the polyvinyl alcohol to the polymerized monomer is (0.6 to 2.4):1.

[0040] In some embodiments of the present invention, the conductive hydrogel is prepared by using the above-mentioned method for preparing the conductive hydrogel.

[0041] According to the third aspect of the present invention, the present invention proposes a massage device. According to an embodiment of the present invention, the massage device includes a massage device body, electrodes arranged on the massage device body, and a conductive hydrogel adhered to the electrodes, wherein the conductive hydrogel is a conductive hydrogel or a conductive hydrogel prepared by the above-mentioned method for preparing a conductive hydrogel. Compared with the prior art, the massage device is based on the advantages of unidirectional conductivity and high strength of the conductive hydrogel. Not only can the conductive hydrogel have better conductivity in the direction of use, thereby producing a more comfortable experience, but also does not require additional non-woven fabrics or other materials to increase strength. When it is used on a massage head with multiple electrodes in a massage device, the installation problem can be solved at one time, and the operation is convenient and quick.

[0042] In some embodiments of the present invention, the massage device further comprises a conductive adhesive, and the conductive hydrogel is adhered to the electrode through the conductive adhesive.

[0043] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0045] Figure 1 The present invention is a flow chart of a method for preparing a conductive hydrogel according to an embodiment of the present invention.

[0046] Figure 2 Schematic diagram of the structure of a device for performing freezing treatment according to an embodiment of the present invention.

[0047] Figure 3 Schematic diagram of the oriented crystallization of conductive hydrogel according to one embodiment of the present invention. DETAILED DESCRIPTION

[0048] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0049] According to the first aspect of the present invention, the present invention proposes a method for preparing a conductive hydrogel. According to an embodiment of the present invention, the preparation method can not only achieve the differentiation of longitudinal and transverse conductivity of the conductive hydrogel, but also the strength of the prepared conductive hydrogel is very good, and no additional non-woven fabric or other materials are required to increase the strength. When it is used in a massager, the installation problem can be solved at one time, which is not only convenient and fast, but also more comfortable to experience. Figures 1 to 3 The method for preparing the conductive hydrogel according to the above embodiment of the present invention is described in detail. According to the embodiment of the present invention, the method comprises:

[0050] S100: Mix polyvinyl alcohol, moisture humectant and water and stir to obtain a first mixed solution

[0051] According to an embodiment of the present invention, polyvinyl alcohol can be dissolved in an aqueous solution of a moisture-humectant to form a uniform and stable first mixed solution. In order to solve the problem of poor mechanical properties of existing conductive hydrogels, the inventors conceived that polyvinyl alcohol can be used as a hard monomer to improve the hardness of the conductive hydrogel, and the polymerization of the polymerized monomer can be used to improve the toughness of the conductive hydrogel to make up for the lack of toughness of the hard monomer. The two can cooperate with each other as film-forming materials to obtain a conductive hydrogel with both toughness and hardness, thereby solving the problem of poor mechanical properties of existing conductive hydrogels without the need for additional non-woven fabrics or other materials to increase strength. Compared with hydrogel materials with polyacrylamide as the main component, the use of polyvinyl alcohol and polymerized monomers as a film-forming material in the present invention can significantly improve the mechanical properties of the hydrogel material, and the material strength is high, and no additional supporting substrate is required. Therefore, when the conductive hydrosol prepared later is used in a massage device, the problem of inconvenient operation of the existing conductive hydrogel during use can be effectively solved.

[0052] According to an embodiment of the present invention, the conductivity of the conductive hydrogel is mainly achieved by utilizing the water and water-soluble inorganic salts contained therein. In the process of preparing the conductive hydrogel, the use of water is not only to dissolve the film-forming material polyvinyl alcohol and the polymerized monomer, but also to dissolve the inorganic salt to provide conductive ions and realize the conductivity of the conductive hydrogel; and the moisture humectant is mainly used to reduce the loss of water in the conductive hydrogel, ensure the conductive stability of the conductive hydrogel, and avoid the problem of shortening the service life of the conductive hydrogel and deteriorating the use effect due to excessive water loss. It should be noted that the types of moisture humectants and water used in the present invention are not particularly limited, and those skilled in the art can select them according to actual needs. For example, the moisture humectant can be at least one selected from glycerol, methyl propanediol, 1,3-propylene glycol and 1,2-hexanediol, and the water can be at least one selected from ultrapure water, distilled water and deionized water, wherein the use of the above-mentioned types of moisture humectants can further improve the water retention of the conductive hydrogel, and the use of the above-mentioned types of water can further avoid the negative impact of impurities or impurity ions in the water on the conductivity of the conductive hydrogel.

[0053] According to a specific embodiment of the present invention, polyvinyl alcohol, a moisture humectant and water can be mixed and stirred at 80-100°C. For example, the mixing temperature can be 80°C, 84°C, 88°C, 92°C, 96°C or 100°C, and the stirring time can be 0.5-3h, for example, 0.5h, 1h, 1.5h, 2h, 2.5h or 3h, etc. The inventors have found that by controlling the above-mentioned mixing temperature, it is more conducive to the full dissolution of polyvinyl alcohol and improve its dissolution efficiency; and by controlling the above-mentioned stirring time, it can be further ensured that polyvinyl alcohol, a moisture humectant and water can be fully mixed so as to obtain a uniform and stable first mixed solution; further, the average molecular weight of polyvinyl alcohol can be no more than 130,000, for example, it can be 10,000, 15,000, 20,000, 50,000, 80,000, etc. The inventors also found that the molecular weight of polyvinyl alcohol has a significant relationship with its crystallinity and the conductivity of the conductive hydrogel finally obtained. With the increase of its molecular weight, its crystallization rate gradually decreases, which directly affects the efficiency and effect of the oriented crystallization of the conductive hydrogel liquid, and then affects the conductivity and the ratio of the longitudinal and transverse conductivity of the conductive hydrogel, and finally affects the experience of the conductive hydrogel when used in the massager. In the present invention, by controlling the average molecular weight of polyvinyl alcohol to be within the above range, it is more conducive to improving the oriented crystallization effect of the conductive hydrogel and obtaining a more obvious longitudinal conductive advantage; preferably, the average molecular weight of polyvinyl alcohol can be 50,000 to 130,000, thereby further making the conductive hydrogel finally obtained have a higher conductivity and a higher ratio of the longitudinal and transverse conductivity.

[0054] According to another specific embodiment of the present invention, 2 to 5 parts by weight of a moisture-keeping agent can be mixed with 5 to 8 parts by weight of water in advance to obtain a moisture-keeping agent aqueous solution with a concentration of 20 to 50 wt%, and then 0.5 to 2 parts by weight of polyvinyl alcohol can be mixed with the moisture-keeping agent aqueous solution, wherein the weight parts of the moisture-keeping agent can be 2, 2.5, 3, 3.5, 4, 4.5 or 5, etc., the weight parts of water can be 5, 5.5, 6, 6.5, 7, 7.5 or 8, etc., and the weight parts of polyvinyl alcohol can be 0.5, 0.8, 1.1, 1.4, 1.7 or 2, etc. The inventors have found that by mixing the moisture-keeping agent with water in advance and then dissolving the polyvinyl alcohol, it is not only more conducive to the full contact between the moisture-keeping agent and the polyvinyl alcohol, but also can avoid the loss of water during the heating and mixing process. In addition, the inventors have also found that when polyvinyl alcohol is used as a film-forming substance and a hard monomer, if its dosage is too small, the mechanical properties and strength of the conductive hydrogel are also poor, and its film-forming property will also be affected to a certain extent. At the same time, it will also affect the freezing of the conductive hydrogel finally prepared at low temperatures, affect its internal crystal orientation and the conductive effect of the conductive hydrogel, and if its dosage is too large, it will cause the viscosity of the conductive hydrogel surface to be too low; and the moisture retaining agent is mainly used to prevent the loss of water in the conductive hydrogel. If its dosage is too small, it is difficult to have an obvious water retention effect and cannot effectively solve the problem of excessive water loss in the conductive hydrogel. If its dosage is too large, the entire conductive body will be The conductivity of the system and the conductive hydrogel deteriorates, and the problem of moisture humectant precipitation is also prone to occur; if the amount of water used is too little, it will not only increase the difficulty of dissolving raw materials such as polyvinyl alcohol and polymerization monomers, but also limit the range of ion activity in the conductive hydrogel, and the conductivity and electrical performance experience of the hydrogel are both poor. If the amount of water used is too much, the water content of the hydrogel will be too high, and water itself is easy to volatilize. The higher the water content of the hydrogel, the greater its water loss rate, which affects the stability and performance of the hydrogel. In the present invention, by controlling the relative amounts of polyvinyl alcohol, moisture humectant and water to the above, it is more conducive to obtaining a conductive hydrogel with expected conductivity, water retention and expected PVA crystal orientation.

[0055] S200: Mixing the polymerizable monomer, the crosslinking agent, the photoinitiator, and the water-soluble inorganic salt with the first mixed solution and stirring to obtain a second mixed solution.

[0056] According to an embodiment of the present invention, the polymerized monomer acts as a film-forming substance to provide flexibility for the conductive hydrogel, and the cross-linking agent is used to cross-link and polymerize the linear polyvinyl alcohol and the monomer polymer to form a mutually entangled three-dimensional network, thereby improving the strength and hardness of the conductive hydrogel; the photoinitiator is used to generate free radicals, initiate the polymerization of the polymerized monomer, and promote film formation; the water-soluble inorganic salt is used to provide conductivity, and the network formed by the polyvinyl alcohol connected by the cross-linking agent and the network formed by the polymerized monomer by the cross-linking agent are mutually entangled to obtain a double three-dimensional network structure, which can give the hydrogel material efficient water retention and excellent mechanical properties, and no additional skeleton support is required to compensate for the strength of the material itself when it is used. Wherein, when the above components are mixed with the first mixed solution, the stirring time can be 30 to 50 minutes, for example, 35 minutes, 40 minutes or 45 minutes, etc., thereby further ensuring the full dissolution and uniform mixing of each component.

[0057] According to a specific embodiment of the present invention, the type of polymerizable monomer used in the present invention is not particularly limited, and those skilled in the art can select it according to actual needs. For example, the polymerizable monomer can be at least one selected from acrylamide, sodium acrylate and chitosan. The inventors have found that the selection of the polymerizable monomer will also have different degrees of influence on the water retention and other properties of the conductive hydrogel. For example, when acrylamide, sodium acrylate or chitosan is selected to prepare the conductive hydrogel, the water retention of the obtained conductive hydrogel is better, and when acrylamide is selected as the polymerizable monomer, the AC impedance of the obtained conductive hydrogel is also lower. Further, considering that acrylamide has low toxicity and a certain sensitizing effect on the skin, the polymerizable monomer can also be preferably sodium acrylate and / or chitosan.

[0058] According to another specific embodiment of the present invention, the types of crosslinking agents and photoinitiators used in the present invention are not particularly limited, and those skilled in the art can select them according to actual needs. For example, the crosslinking agent can be at least one selected from polyamides, aliphatic amines, aromatic amines and polyether amines, and the photoinitiator can be at least one selected from the group consisting of 2959 (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone), 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone), 907 (2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone) and 184 (1-hydroxycyclohexylphenyl ketone). In the present invention, the crosslinking agent and photoinitiator can be selected from the group consisting of 2959 (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone), 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone), 907 (2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone) and 184 (1-hydroxycyclohexylphenyl ketone). The above-mentioned types of photoinitiators not only have an absorption wavelength that meets the requirements of ultraviolet lamp irradiation, but also have the advantages of low odor and / or high efficiency without yellowing. When used in conductive hydrogels, they are not only more conducive to generating free radicals to promote polymerization of polymerization monomers and improve film-forming properties, but also do not affect the odor and color of the hydrogel. For example, the photoinitiator with a brand name of 2959 has an absorption wavelength in the range of 200 to 370 nanometers, which not only meets the requirements of ultraviolet lamp irradiation, but also has the advantages of low odor, high efficiency and no yellowing. It is particularly suitable for hydrogel systems. The use of the above-mentioned types of cross-linking agents is more conducive to promoting the cross-linking polymerization of linear polyvinyl alcohol and monomer polymers and forming a uniform and stable double three-dimensional network structure, so that the mechanical properties and strength of the conductive hydrogel in all directions are more uniform.

[0059] According to another specific embodiment of the present invention, the type of water-soluble inorganic salt used in the present invention is not particularly limited, and those skilled in the art can select it according to actual needs. For example, the inorganic salt can be sodium chloride and / or lithium chloride. Preferably, the inorganic salt can also be lithium chloride. The inventors have found that lithium chloride not only has better conductivity, but also does not affect the solubility of the polymerized monomer (such as sodium acrylate), thereby further ensuring the conductive properties, film-forming properties and mechanical properties of the conductive hydrogel.

[0060] According to another specific embodiment of the present invention, based on 0.5 to 2 parts by weight of polyvinyl alcohol, 0.5 to 2 parts by weight of a polymerizable monomer, 0.015 to 0.025 parts by weight of a cross-linking agent, 0.005 to 0.02 parts by weight of a photoinitiator, and 0.5 to 2 parts by weight of an inorganic salt can be dispersed in the first mixed solution in sequence, wherein the mass ratio of polyvinyl alcohol to the polymerizable monomer can be (0.6 to 2.4): 1, for example, the weight ratio of polyvinyl alcohol can be 0.5, 0.8, 1.1, 1.4, 1.7 or 2, and the weight ratio of the cross-linking agent can be (0.6 to 2.4): 1. The weight proportions can be 0.015, 0.017, 0.019, 0.021, 0.023 or 0.025, etc., the weight proportions of the photoinitiator can be 0.005, 0.008, 0.011, 0.014, 0.017 or 0.02, etc., the weight proportions of the inorganic salt can be 0.5, 0.8, 1.1, 1.4, 1.7 or 2, etc., and the mass ratio of polyvinyl alcohol to the polymerization monomer can be 0.6 / 1, 0.9 / 1, 1.2, 1.5 / 1, 1.8 / 1, 2.1 / 1 or 2.4 / 1, etc. The inventors have found that the difficulty of dissolving the polymerized monomer is usually the highest, while the photoinitiator is easy to decompose under the illumination of a specific wavelength. The inorganic salt is an ionic compound with good dispersibility. In the present invention, by dispersing the polymerized monomer, the crosslinking agent, the photoinitiator and the inorganic salt in the first mixed solution in sequence, it is not only convenient to operate, but also more conducive to improving the mixing uniformity of each component and reducing the loss of the photoinitiator. In addition, the inventors have also found that if the amount of crosslinking agent is too much, it will lead to excessive crosslinking, and the density of the three-dimensional network structure formed will be too large, resulting in a too hard hydrogel system. If the crosslinking agent is too little, the three-dimensional network formed will be incomplete, the mechanical properties of the hydrogel will deteriorate, and it will be very easy to break and damage under the action of external force extrusion; if the amount of photoinitiator is too little, the free radicals generated will also be less, and the polymer formed by the monomer will also be less, which is not conducive to improving the strength and polymerization degree of the conductive hydrogel; if the amount of inorganic salt is too little, it will affect the macroscopic conductivity. As the amount of inorganic salt increases, although the conductivity of the hydrogel can be improved, if the amount of inorganic salt is too high, it will not be It will not only affect the solubility of the polymerized monomer, but also increase the cost of raw materials. For example, when sodium chloride is selected as the inorganic salt, the solubility of the polymerized monomer sodium acrylate will be affected, and the low solubility of the polymerized monomer will also lead to a decrease in the degree of polymerization of the monomer; in addition, if the mass ratio of polyvinyl alcohol to the polymerized monomer is too large, it is easy to cause the overall performance of the hydrogel material to be hard, without flexibility, and poor water retention, and it is easy to dry on the surface. If the mass ratio of polyvinyl alcohol to the polymerized monomer is too small, although the hydrogel material has excellent tensile strength, it is not conducive to using polyvinyl alcohol to form an oriented conductive channel inside the hydrogel, and the surface of the obtained hydrogel is also easy to dry. In the present invention, by controlling the raw material components to the above ratio, the conductive hydrogel finally obtained can have good film-forming properties, conductivity, water retention and mechanical properties.

[0061] According to an embodiment of the present invention, functional additives may be further added to the second mixed liquid, wherein the functional additives may include at least one of fragrances, cooling agents and skin conditioning agents. In the present invention, by adding fragrances, the finally prepared conductive hydrogel can have a desired fragrance, such as floral fragrance, fruity fragrance, etc.; by adding cooling agents, the finally prepared conductive hydrogel can have a cool touch; by adding skin conditioning agents, the finally prepared conductive hydrogel can have a certain skin conditioning effect.

[0062] According to a specific embodiment of the present invention, the types of fragrances, cooling agents and skin conditioning agents in the present invention are not particularly limited, and those skilled in the art can select them according to actual needs. For example, the fragrance can be plant fragrance, animal fragrance, natural fragrance or artificial fragrance, etc., such as at least one selected from essence, balsam, essential oil and plant extract, so that the conductive hydrogel can emit a certain fragrance according to different needs; for another example, the cooling agent can include at least one of mint essence, menthol and menthol, so that the conductive hydrogel can have a certain mint fragrance and a certain cool touch. In addition, it should be noted that the amount of functional additives added in the present invention is not particularly limited, and those skilled in the art can select them according to actual needs. For example, the amount of cooling agent added can be no more than 0.1wt% of the unidirectional conductive hydrogel, and the amount of fragrance added can be no more than 0.1wt% or 0.1mL of the unidirectional conductive hydrogel, so that the conductive hydrogel can be given a specific functional effect without significantly affecting the performance of the conductive hydrogel itself.

[0063] S300: Performing UV cross-linking film-forming treatment on the second mixed solution to obtain a precursor film

[0064] According to an embodiment of the present invention, the ultraviolet cross-linking film-forming treatment can be achieved by ultraviolet lamp irradiation, wherein the ultraviolet cross-linking time and the controlled illumination power can be selected according to the actual needs such as the film thickness. It is expected that the greater the film thickness, the greater the illumination time required under the same illumination power and the illumination power required under the same illumination time. For example, when the film thickness is 0.6 to 1.2 mm, such as 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm or 1.2 mm, etc., the ultraviolet cross-linking time can be 0.5 to 2 min, such as 0.5 min, 0.8 min, 1.1 min, 1.4 min, 1.7 min or 2 min, etc., and the ultraviolet lamp power can be 0.1 to 4 KW, such as 0.1 KW, 0.5 KW, 1 KW, 1.5 KW, 2 KW, 2.5 KW, 3 KW, 3.5 KW or 4 KW, etc. The inventors found that Both the UV cross-linking time and the UV irradiation power will affect the degree of cross-linking. Under the same film thickness, the smaller the UV irradiation power, the longer the UV cross-linking time required. Although increasing the UV irradiation power can shorten the UV cross-linking time, if the UV irradiation power is too large, it will lead to excessive cross-linking. At the same time, too long UV cross-linking time will also lead to excessive cross-linking, which will cause the conductive hydrogel to be too hard and affect the touch of the conductive hydrogel. Based on the film thickness of 0.6 to 1.2 mm, the present invention controls the above-mentioned UV cross-linking conditions, which can not only promote the cross-linking film formation of the second mixed liquid, but also avoid the problem of excessive cross-linking.

[0065] According to a specific embodiment of the present invention, the ultraviolet cross-linking film-forming treatment of the second mixed liquid may further include: (3-1) using a heat conductive plate as a bottom plate and using a fixed plate to define a hydrogel forming area; (3-2) transferring the second mixed liquid to the hydrogel forming area and covering it with a transparent cover plate, preferably with the cover plate covering the middle of the hydrogel forming area; (3-3) fixing the heat conductive plate and the transparent cover plate; (3-4) subjecting the second mixed liquid to ultraviolet irradiation through the transparent cover plate so that the second mixed liquid is cross-linked to form a film to obtain a precursor film. The above operation has the following advantages: on the one hand, by using the heat conductive plate as the bottom plate, the second mixed liquid can be cross-linked to form a film on the heat conductive plate, so that the heat conductive plate can be directly subjected to low-temperature treatment to achieve freezing treatment of the precursor film; on the other hand, the transparent cover plate can be used in combination with the conductive plate to control the flatness of the conductive hydrogel finally obtained, and in this process, the use of the transparent cover plate can also press out the bubbles that may appear in the second mixed liquid; and by fixing the heat conductive plate and the transparent cover plate, the flatness and uniformity of the conductive hydrogel finally obtained can be further ensured.

[0066] According to another specific embodiment of the present invention, a conductive hydrogel of a desired thickness and shape can be obtained by controlling the height and shape of the hydrogel forming area. Preferably, the second mixed liquid can be made flush with the height of the hydrogel forming area, and the height of the fixing plate located on the heat conductive plate can be made the same as the thickness of the conductive hydrogel, thereby more advantageously obtaining a conductive hydrogel of a desired thickness.

[0067] According to another specific embodiment of the present invention, the heat conducting plate and the transparent cover plate can be fixed by a fixing clamp or a counterweight. For example, the clamp can be fixed in the middle of the heat conducting plate and the transparent cover plate, etc., which can further help improve the flatness and uniformity of the conductive hydrogel finally obtained. It should be noted that the materials of the heat conducting plate, the fixing plate and the transparent cover plate used in the present invention are not particularly limited, and those skilled in the art can choose according to actual needs. For example, the heat conducting plate can be a copper plate, etc., which not only has good thermal conductivity but also has a low price; the fixing plate can be a silicone template, and the transparent cover plate can be a glass plate, etc.

[0068] S400: freezing the precursor film, keeping one side of the precursor film at room temperature and the other side at low temperature during the freezing process, so that the precursor film is frozen from the low temperature side to the room temperature side, and obtaining a conductive hydrogel

[0069] According to the embodiment of the present invention, the inventors found that, compared with placing the precursor film in an isotropically uniform freezing environment, by making the upper and lower sides of the precursor film have a specific temperature difference, the freezing direction can be controlled to gradually proceed from the low temperature side to the normal temperature side. In this process, the liquid in the conductive hydrogel freezes from the low temperature side to the normal temperature side in a directional manner and forms a corresponding icicle, providing more ion channels for the conductive ions in the thickness direction of the conductive hydrogel. Since polyvinyl alcohol is a polymer material, after the ion channels are formed, even if the conductive hydrogel returns to room temperature, the ion channels that have been established will not disappear, thereby significantly improving the conductivity of the conductive hydrogel in the longitudinal direction, making its longitudinal conductivity significantly superior to the transverse conductivity, and greatly improving the unidirectional conductive effect of the conductive hydrogel. Therefore, in the present invention, by adopting a temperature difference freezing process, the internal structure of the hydrogel can undergo a significant orientation change, and the conductive ion direction can be arranged in a specific manner according to a predetermined direction, thereby improving the longitudinal conductivity and sensing sensitivity, and realizing the differentiation of the conductive direction in the longitudinal and transverse directions.

[0070] According to a specific embodiment of the present invention, when the thickness of the precursor film is 0.6 to 1.2 mm, the temperature of the freezing treatment can be -80 to -200°C, for example, -80°C, -100°C, -120°C, -140°C, -160°C, -180°C or -200°C, etc., and the time can be 3 to 10 minutes, for example, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes, etc. The inventors have discovered that when a precursor film is frozen using a temperature difference freezing process, the temperature and time of the freezing treatment will significantly affect the crystallization effect of the liquid in the precursor film, and the thickness of the precursor film is different, and the required optimal freezing conditions are also different. For example, at the same freezing time, the lower the freezing temperature on the low-temperature side, the better the oriented crystallization effect of the liquid in the conductive hydrogel; and at the same freezing temperature, the longer the freezing time, the better the oriented crystallization effect of the liquid in the conductive hydrogel. However, when the freezing time is extended to a certain time, continuing to extend the freezing time does not cause further significant changes in the oriented crystallization effect of the conductive hydrogel. In the present invention, for a precursor film with a thickness of 0.6 to 1.2 mm, by controlling the freezing treatment to the above-mentioned temperature and time range, the conductive hydrogel can produce a significant oriented crystallization effect and obtain a better longitudinal conductive effect. Preferably, for a precursor film with a thickness of 0.6 to 1.2 mm, the freezing treatment temperature can be -150 to -200°C, and the time can be 5 to 8 minutes. For example, the freezing treatment temperature can be -196°C, and the time can be 6 minutes. This can further improve the oriented crystallization effect of the conductive hydrogel and ensure the freezing efficiency, thereby further improving its longitudinal conductivity.

[0071] According to another specific embodiment of the present invention, based on the product obtained in step (3-4), one side of the transparent cover plate can be kept at room temperature, and the precursor film can be frozen by liquid nitrogen through a heat conducting plate, so that the conductive hydrogel produces an excellent oriented crystallization effect. It should be noted that the thickness of the conductive hydrogel in the present invention is not particularly limited, and those skilled in the art can select it according to actual needs.

[0072] According to another specific embodiment of the present invention, Figure 2As shown, the device for freezing treatment may include: a freezer and a cold source storage tank, wherein the freezer may include a freezing tank, the freezing tank is suitable for accommodating a cold source, so that the freezing tank is a low-temperature constant temperature environment, a cold source port is provided at the bottom of the freezing tank, and a support structure is formed at the top of the freezing tank, the support structure is suitable for supporting the conductive hydrogel precursor film or the heat conductive plate and closing the freezing tank in combination with the conductive hydrogel or the heat conductive plate; the cold source storage tank is connected to the cold source port through a pipeline, and a cold source flow control valve is provided on the pipeline. Therefore, when the precursor film is subjected to freezing treatment, the precursor film or the precursor film fixed by the heat conductive plate, the fixing plate and the transparent cover plate can be transferred to the top of the freezing tank, and the top of the freezing tank is kept at a normal temperature environment. The cold source flow control valve is opened to supply a cold source, such as liquid nitrogen, to the freezing tank, so that a low-temperature environment is formed in the freezing tank, so that the freezing direction of the precursor film is from bottom to top, and the oriented crystallization direction and principle of the precursor film are as shown in FIG. Figure 3 As shown, a better ion conduction path can be formed in the thickness direction of the precursor film.

[0073] According to another specific embodiment of the present invention, the structure of the freezing tank in the present invention is not particularly limited, and those skilled in the art can select it according to actual needs, as long as it can achieve the temperature difference freezing effect of the precursor film. For example, the freezing tank may include a Dewar flask, etc.

[0074] According to another specific embodiment of the present invention, in order to facilitate the control of the supply amount of the cold source in the freezing tank, a liquid level sensor may be further provided in the freezing tank, and the opening or closing of the cold source flow control valve is controlled based on the display of the liquid level sensor so that there is enough cold source in the freezing tank. Preferably, the cold source may be liquid nitrogen.

[0075] In summary, the method for preparing a conductive hydrogel according to the above embodiment of the present invention has at least the following advantages: on the one hand, polyvinyl alcohol and a polymerized monomer are compounded as film-forming materials in the formula system, and the network structure formed by the cross-linking polymerization of polyvinyl alcohol and the network structure formed by the cross-linking polymerization of the polymerized monomer are intertwined to form a double three-dimensional network structure, which gives the hydrogel material efficient water retention and excellent mechanical properties, and no additional skeleton support is required to make up for the strength of the hydrogel material itself; on the other hand, the temperature difference freezing process is used to make the internal structure of the hydrogel undergo a significant orientation change, and the direction of the conductive ions can be arranged in a specific manner according to a predetermined direction, thereby improving the conductivity and sensing sensitivity. Compared with the current situation that the existing hydrogel is homogeneously conductive, that is, the lateral and longitudinal conductivity are consistent, the conductive hydrogel prepared in the present invention has strong longitudinal conductivity and poor lateral conductivity, which can better realize the differentiation of the conductive direction. Using it in a massage device can produce a more comfortable experience strength, and solves the current situation that the existing conductive hydrogel cannot be partitioned into a single piece to achieve a multi-electrode EMS massage effect. Therefore, this method can not only achieve the differentiation of longitudinal and transverse conductivity of conductive hydrogels, but also the produced conductive hydrogel has very good strength and does not require additional non-woven fabrics or other materials to increase the strength. When it is used in a massager, the installation problem can be solved at one time. It is not only convenient and fast, but also the experience of strength is more comfortable.

[0076] It should be noted that the "longitudinal conductivity" described in the present invention refers to the conductivity in the thickness orientation of the conductive hydrogel, which is achieved by taking the thickness direction of the conductive hydrogel as the freezing crystallization direction. Those skilled in the art can understand that the temperature difference freezing process of the present invention can not only achieve the excellent conductivity of the conductive hydrogel in its thickness direction, but also achieve its excellent conductivity in other specific directions, and it only needs to control its freezing crystallization direction.

[0077] According to a second aspect of the present invention, the present invention provides a conductive hydrogel. According to an embodiment of the present invention, the conductive hydrogel comprises: polyvinyl alcohol, a polymerized monomer, a cross-linking agent, a photoinitiator, a water-soluble inorganic salt, a moisture humectant and water, the conductive hydrogel has a microscopic porous structure in thickness orientation, and the conductive hydrogel has different conductivity in its surface orientation and thickness orientation. Compared with the prior art, the hydrogel material uses polyvinyl alcohol as the main component. Polyvinyl alcohol is not only an extremely safe macromolecular organic substance, non-toxic to the human body, has no side effects, and has good biocompatibility, but also a double three-dimensional network structure formed by the intertwining of the network structure formed by the cross-linking polymerization of polyvinyl alcohol and the network structure formed by the cross-linking polymerization of the polymerized monomer, which gives the hydrogel material efficient water retention and excellent mechanical properties. No additional skeleton support (such as non-woven fabric or other materials) is required to make up for the strength of the hydrogel material itself, and it is more suitable for use in massagers. When it is used in massagers, the installation problem can be solved at one time, which is convenient and quick; further, the conductive hydrogel has a microscopic porous structure oriented perpendicular to the surface, which can form a directional conductive channel, so that the conductivity of the conductive hydrogel in its thickness orientation is significantly higher than its conductivity in the surface orientation, and using it in a massager can produce a more comfortable experience; in addition, the conductive hydrogel also has a certain viscosity and can adhere to a variety of substrates, such as metal, plastic, skin and other surfaces to form stable and reversible adhesion. It should be noted that the inventive concept of the conductive hydrogel is the same as the method for preparing the conductive hydrogel mentioned above. The characteristics and effects described for the method for preparing the conductive hydrogel mentioned above are also applicable to the conductive hydrogel, and will not be described in detail here.

[0078] It should be noted that the microporous structure of the conductive hydrogel in the thickness orientation of the present invention provides more conductive paths for the conductive ions along the thickness direction, so that the conductivity of the conductive ions in the thickness direction (i.e., longitudinal direction) of the hydrogel is better, which is significantly better than its conductivity in the surface orientation (i.e., transverse direction). The microporous structure can be formed by the oriented crystallization of materials such as polyvinyl alcohol in the raw material mixture under the temperature difference freezing process. It is the microstructure inside the conductive hydrogel and does not affect the flatness of the surface of the conductive hydrogel.

[0079] According to a specific embodiment of the present invention, the conductive hydrogel comprises: 2 to 5 parts by weight of a moisture humectant, 5 to 8 parts by weight of water, 0.5 to 2 parts by weight of polyvinyl alcohol, 0.5 to 2 parts by weight of a polymerized monomer, 0.015 to 0.025 parts by weight of a cross-linking agent, 0.005 to 0.02 parts by weight of a photoinitiator, and 0.5 to 2 parts by weight of an inorganic salt, and the mass ratio of polyvinyl alcohol to the polymerized monomer is (0.6 to 2.4): 1. In the present invention, by controlling the above-mentioned raw material ratio, it can be further ensured that the conductive hydrogel has good longitudinal conductivity, which is significantly different from the transverse conductivity, and the network structure formed by the cross-linking polymerization of polyvinyl alcohol and the network structure formed by the cross-linking polymerization of the polymerized monomer are intertwined to form a double three-dimensional network structure, which gives the hydrogel material efficient water retention and excellent mechanical properties, and does not require an additional skeleton support (such as non-woven fabric or other materials) to make up for the strength of the hydrogel material itself. When it is used in a massager, the installation problem can be solved at one time, which is not only convenient and fast, but also more comfortable to experience.

[0080] According to another specific embodiment of the present invention, the conductive hydrogel can be prepared by the above-mentioned method for preparing conductive hydrogel, which can further facilitate obtaining a conductive hydrogel having excellent properties such as good longitudinal conductivity, mechanical strength, and water retention.

[0081] According to the third aspect of the present invention, the present invention proposes a massage device. According to an embodiment of the present invention, the massage device includes a massage device body, electrodes arranged on the massage device body, and a conductive hydrogel adhered to the electrodes, wherein the conductive hydrogel is the above-mentioned conductive hydrogel or a conductive hydrogel prepared by the above-mentioned method for preparing conductive hydrogel. Compared with the prior art, the massage device is based on the advantages of unidirectional conductivity and high strength of the conductive hydrogel, which can not only make the conductive hydrogel have better conductivity in the direction of use, thereby producing a more comfortable experience, but also does not require additional non-woven fabrics or other materials to increase the strength. When it is used on a massage head with multiple electrodes in a massage device, the installation problem can be solved at one time, and the operation is convenient and quick. It should be noted that the characteristics and effects described for the above-mentioned conductive hydrogel and the method for preparing the conductive hydrogel are also applicable to the massage device, and will not be repeated here one by one.

[0082] According to a specific embodiment of the present invention, the massage device may include a conductive glue, and the conductive hydrogel may be adhered to the electrode through the conductive glue. The inventor found that compared with the existing conductive hydrogel, the conductive hydrogel obtained by the preparation method of the above embodiment of the present invention has relatively poor viscosity. When it is used in a massage device, the problem of hydrogel falling off due to insufficient adhesion may occur. By using conductive glue as the intermediate layer adhesive, it does not affect the conductivity of the entire system and can also make the conductive hydrogel stably adhere to the electrode of the massage device.

[0083] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0084] General approach

[0085] The method for preparing a conductive hydrogel comprises: 1) first mixing a moisture-moisturizing agent with water to obtain a moisture-moisturizing agent aqueous solution, then dissolving polyvinyl alcohol in the moisture-moisturizing agent aqueous solution at 80-100° C., stirring for 0.5-3 hours, and obtaining a first mixed solution; 2) sequentially adding acrylamide monomer, a crosslinking agent, a photoinitiator, and a water-soluble inorganic salt to the first mixed solution, stirring and dissolving for 30-50 minutes, and obtaining a second mixed solution; 3) adding 1 drop of mint essence (about 0.05 mL) to the second mixed solution; 4) placing a fixing plate on a heat-conducting plate so that the height of the fixing plate on the heat-conducting plate is the same as the expected thickness of the hydrogel, pouring the liquid obtained in step 3) on the heat-conducting plate, covering it with a transparent and flat glass cover plate, being careful not to form bubbles, fixing the cover plate and the heat-conducting plate with a fixing clamp or a heavy object after covering the cover plate, and UV crosslinking for 0.5-2 minutes, with a UV lamp power of 0.1-4KW. 5) Move the fixing clip to the middle as far as possible, fill the Dewar flask with liquid nitrogen, place the heat transfer plate downward and the cover plate upward on the Dewar flask, and freeze for 3 to 10 minutes; this makes the temperature of the side close to the heat transfer plate be -80℃ to -200℃, and the other side be at room temperature, so that the liquid freezes from bottom to top, forming corresponding icicles.

[0086] Examples 1 to 3

[0087] The raw material ratios and evaluation results of Examples 1 to 3 are shown in Table 1. Among them, the process parameter conditions controlled in Examples 1 to 3 are the same, the polyvinyl alcohol dissolution temperature in step 1) is 90°C, the stirring time is 2h, and the molecular weight of polyvinyl alcohol is 77000; the stirring and dissolving time in step 2) is 40min; the ultraviolet crosslinking time in step 4) is 1.5min, and the UV lamp power is 0.2KW; in step 5), the freezing time is 6min and the freezing temperature is -196°C; the thickness of the obtained conductive hydrogel is 1mm. Among them, the experience strength is tested by using the obtained conductive hydrogel in a massager.

[0088] Table 1 Comparison of raw material ratios and evaluation results of conductive hydrogels prepared in Examples 1 to 3

[0089]

[0090] It can be seen from Examples 1 to 3 that the conductive hydrogels prepared in Examples 1 to 3 have obtained obvious unidirectional conductive advantages, the longitudinal conductivity is significantly higher than the transverse conductivity, and the mechanical properties are good and the low-frequency current stimulation is obvious. This shows that the use of the technical solution of the present invention can achieve the differentiation of longitudinal and transverse conductivity of the conductive hydrogel, and has obvious longitudinal conductive advantages. Moreover, the mechanical properties of the conductive hydrogel prepared are very good, and no additional non-woven fabric or other materials are provided to increase the strength. When it is used in a massager, the experience strength is also more comfortable. Further, by comparing the evaluation results of Examples 1 to 3, it can be seen that the selection of polymerized monomers will have a certain effect on the water retention and cross-linking impedance of the conductive hydrogel. The conductive hydrogels prepared by using hydroxyethyl methacrylate and methyl methacryloylethyl sulfonyl betaine as polymerized monomers are easy to lose water, have poor water retention, and are not suitable for long-term use; in addition, the AC impedance of the conductive hydrogel prepared by using methyl methacryloylethyl sulfonyl betaine as a polymerized monomer is relatively high. Relatively speaking, the comprehensive performance of the conductive hydrogel prepared by using acrylamide monomer is better.

[0091] Example 4 and Comparative Examples 1-2

[0092] The raw material ratios and evaluation results of Example 4 and Comparative Examples 1-2 are shown in Table 2. The process parameters controlled during the preparation process are the same as those of Example 1.

[0093] Table 2 Comparison of raw material ratios and evaluation results of conductive hydrogels prepared in Example 1, Example 4 and Comparative Examples 1-2

[0094]

[0095] It can be seen from Examples 1, 4 and Comparative Examples 1 to 2 that a mass ratio of polyvinyl alcohol to a polymerized monomer that is too large or too small is not conducive to improving the water retention, conductivity and longitudinal and transverse conductivity ratio of the conductive hydrogel, and it is difficult to obtain a comfortable experience strength. As shown in Table 1, when the mass ratio of polyvinyl alcohol to acrylamide monomer is 1 / 3, the conductive hydrogel obtained is easy to lose water, and the AC impedance is large, there is no obvious difference between the longitudinal conductivity and the transverse conductivity, and the experience strength is not obvious when it is used in a massager; and when the mass ratio of polyvinyl alcohol to acrylamide monomer is 1 / 0.4, the conductive hydrogel obtained is also easy to lose water, and has poor mechanical properties, and the AC impedance is also large. The ratio of longitudinal conductivity to transverse conductivity is only about 1.3, the longitudinal conductivity advantage is not obvious, and the experience strength is not obvious when used in a massager. In fact, the inventors found that the mass ratio of polyvinyl alcohol to polymerized monomers has a significant effect on the water retention, AC impedance, conductivity, mechanical properties and experience strength of the conductive hydrogel. As the mass ratio of polyvinyl alcohol to polymerized monomers increases, the AC impedance of the conductive hydrogel decreases first and then increases, while the longitudinal and transverse conductivity ratio of the conductive hydrogel increases first and then decreases. A large mass ratio of polyvinyl alcohol to polymerized monomers will result in a hard overall performance of the hydrogel material, no flexibility, and poor water retention; while a small mass ratio of polyvinyl alcohol to polymerized monomers, although the hydrogel material has excellent tensile strength, is not conducive to the formation of oriented conductive channels inside the hydrogel, and the surface of the obtained hydrogel is also easy to dry. Relatively speaking, the comprehensive performance of the conductive hydrogel prepared when the mass ratio of polyvinyl alcohol to acrylamide monomers is controlled to be greater than 1 / 3 and less than 1 / 0.4 is better.

[0096] Embodiments 5 to 7

[0097] The difference from Example 1 is that only the freezing process in step 5) is different. The freezing process and the crystallization effect of the obtained conductive hydrogel are shown in Table 3.

[0098] Table 3 Crystallization effect of conductive hydrogel at different freezing temperatures

[0099] Freezing temperature Freezing time Liquid Oriented Crystallization Effect Example 5 -80℃ 3min Difference Example 6 -150℃ 3min good Example 7 -200℃ 3min Excellent

[0100] It can be seen from Table 3 that under the same freezing time, the lower the freezing temperature, the better the liquid orientation crystallization effect of the conductive hydrogel, and thus the longitudinal conductivity of the conductive hydrogel is also better. In fact, when the temperature is higher than minus 80°C, the liquid crystallization effect is poor. The lower the temperature, the more complete the ice pillars formed by the system, and the more obvious the horizontal and vertical conductivity ratio.

[0101] Embodiments 8 to 13

[0102] The difference from Example 1 is that only the freezing process in step 5) is different. The freezing process and the crystallization effect of the obtained conductive hydrogel are shown in Table 4.

[0103] Table 4 Crystallization effect of conductive hydrogel under different freezing time

[0104]

[0105]

[0106] It can be seen from Table 3 that at the same freezing temperature, the longer the freezing time, the better the liquid orientation crystallization effect of the conductive hydrogel, and thus the longitudinal conductivity of the conductive hydrogel is also better; but when the freezing time reaches a certain time, the liquid orientation crystallization is completed and there is no need to continue to extend the freezing time.

[0107] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0108] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a conductive hydrogel, characterized in that: include: (1) mixing polyvinyl alcohol, a moisture humectant and water and stirring to obtain a first mixed solution; (2) mixing a polymerizable monomer, a cross-linking agent, a photoinitiator, and a water-soluble inorganic salt with the first mixed solution and stirring to obtain a second mixed solution; (3) performing ultraviolet cross-linking film-forming treatment on the second mixed solution to obtain a precursor film; (4) subjecting the precursor film to a freezing treatment, wherein one side of the precursor film is kept at a room temperature environment and the other side is kept at a low temperature environment during the freezing treatment, so that the freezing of the precursor film proceeds from the low temperature side to the room temperature side, so as to obtain a conductive hydrogel. Wherein, the mass ratio of the polyvinyl alcohol to the polymerization monomer is (0.6-1.5):1; In step (2), the polymerizable monomer is acrylamide; In step (4), the thickness of the precursor film is 0.6-1.2 mm, the temperature of the freezing treatment is -80-200° C., and the time is 3-10 min.

2. The method according to claim 1, characterized in that In step (1), the moisture humectant includes at least one of glycerol, methyl propanediol, 1,3-propylene glycol and 1,2-hexanediol.

3. The method according to claim 1, characterized in that In step (1), the water includes at least one of ultrapure water, distilled water and deionized water.

4. The method according to claim 1, characterized in that: In step (1), the mixing temperature is 80-100° C. and the stirring time is 0.5-3 h.

5. The method according to claim 1, characterized in that: In step (1), 2 to 5 parts by weight of the moisture-keeping agent and 5 to 8 parts by weight of the water are mixed in advance to obtain a moisture-keeping agent aqueous solution; and then 0.5 to 2 parts by weight of the polyvinyl alcohol are mixed with the moisture-keeping agent aqueous solution.

6. The method according to claim 1, characterized in that In step (2), the cross-linking agent includes at least one of polyamides, aliphatic amines, aromatic amines, and polyether amines.

7. The method according to claim 1, characterized in that In step (2), the photoinitiator includes at least one of brands 2959, 1173, 907 and 184.

8. The method according to claim 1, characterized in that In step (2), the water-soluble inorganic salt includes sodium chloride and / or lithium chloride.

9. The method according to claim 1, characterized in that: In step (2), the stirring time is 30 to 50 minutes.

10. The method according to claim 1, characterized in that In step (2), based on 0.5-2 parts by weight of the polyvinyl alcohol, 0.5-2 parts by weight of the polymerizable monomer, 0.015-0.025 parts by weight of the cross-linking agent, 0.005-0.02 parts by weight of the photoinitiator, and 0.5-2 parts by weight of the inorganic salt are dispersed in the first mixed solution in sequence.

11. The method according to claim 1, characterized in that: Step (2) comprises: adding a functional additive to the second mixed liquid, wherein the functional additive comprises at least one of a fragrance, a cooling agent and a skin conditioner.

12. The method according to claim 11, characterized in that The fragrance comprises at least one of essence, balsam, essential oil and plant extract.

13. The method according to claim 11, characterized in that The cooling agent includes at least one of mint essence, menthol and menthol.

14. The method according to claim 1, characterized in that Step (3) further includes: (3-1) Using the heat conducting plate as the bottom plate and the fixing plate to define the hydrogel forming area; (3-2) transferring the second mixed solution to the hydrogel forming area and covering it with a transparent cover; (3-3) Fixing the heat conducting plate and the transparent cover plate; (3-4) The second mixed liquid is subjected to ultraviolet irradiation through the transparent cover plate so as to cross-link the second mixed liquid into a film to obtain a precursor film.

15. The method according to claim 14, characterized in that The conductive hydrogel with desired thickness and shape can be obtained by controlling the height and shape of the hydrogel forming area.

16. The method according to claim 14, characterized in that The height of the fixing plate located on the heat conducting plate is the same as the thickness of the conductive hydrogel.

17. The method according to claim 16, characterized in that In step (3), the height of the fixing plate is 0.6-1.2 mm, the ultraviolet cross-linking film-forming treatment is achieved by ultraviolet lamp irradiation, the ultraviolet cross-linking time is 0.5-2 min, and the ultraviolet lamp power is 0.1-4 kW.

18. The method according to claim 14, characterized in that The fixing plate is a silicone template, and the transparent cover plate is a glass plate.

19. The method according to claim 14, characterized in that The heat conducting plate and the transparent cover plate are fixed by using a fixing clamp or a counterweight.

20. The method according to claim 14, characterized in that Step (4) comprises: based on the product obtained in steps (3-4), keeping one side of the transparent cover plate at room temperature, and freezing the precursor film using liquid nitrogen through the heat conducting plate.

21. The method according to claim 1, characterized in that The freezing treatment is carried out at a temperature of -150 to -200°C and for a time of 5 to 8 minutes.

22. The method according to claim 1, characterized in that The freezing treatment was carried out at a temperature of -196°C and for 6 minutes.

23. The method according to claim 1 or 20, characterized in that In step (4), the device for performing the freezing treatment includes: A freezer, the freezer comprising a freezing tank, the freezing tank being suitable for accommodating a cold source, a cold source port being provided at the lower portion of the freezing tank, a support structure being formed at the upper portion of the freezing tank, the support structure being suitable for supporting a conductive hydrogel or a heat conductive plate and closing the freezing tank in combination with the conductive hydrogel or the heat conductive plate; A cold source storage tank is connected to the cold source port through a pipeline, and a cold source flow control valve is provided on the pipeline.

24. A conductive hydrogel prepared by the method according to any one of claims 1 to 23, characterized in that: include: Polyvinyl alcohol, a polymerizable monomer, a cross-linking agent, a photoinitiator, a water-soluble inorganic salt, a moisture humectant and water. The conductive hydrogel has a microscopic porous structure in a thickness orientation, and the conductivity of the conductive hydrogel in its surface orientation and thickness orientation is different.

25. The conductive hydrogel according to claim 24, characterized in that include: 2 to 5 parts by weight of the moisture moisturizing agent, 5 to 8 parts by weight of the water, 0.5 to 2 parts by weight of the polyvinyl alcohol, 0.5 to 2 parts by weight of the polymerizable monomer, 0.015 to 0.025 parts by weight of the cross-linking agent, 0.005 to 0.02 parts by weight of the photoinitiator, and 0.5 to 2 parts by weight of the inorganic salt, wherein the mass ratio of the polyvinyl alcohol to the polymerizable monomer is (0.6 to 1.5):

1.

26. A massage device, characterized in that: The massage device comprises a massage device body, an electrode arranged on the massage device body and a conductive hydrogel adhered to the electrode, wherein the conductive hydrogel is the conductive hydrogel according to any one of claims 24 to 25 or the conductive hydrogel prepared by the method according to any one of claims 1 to 23.

27. The massage device according to claim 26, characterized in that It also includes a conductive glue, and the conductive hydrogel is adhered to the electrode through the conductive glue.

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