Composite conductive hydrogel and its preparation method and application

Abstract

The present invention discloses a composite conductive hydrogel and its preparation method and application. The preparation method comprises: mixing polyvinyl alcohol, a moisture humectant and water, and then mixing with a polymerized monomer, a crosslinking agent, a photoinitiator and a water-soluble inorganic salt to obtain a mixed solution; subjecting the mixed solution to ultraviolet crosslinking film-forming treatment, and then subjecting the obtained 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 obtaining a unidirectional conductive hydrogel; mixing the moisture humectant with water, and then mixing with sodium acrylate, an acrylate monomer, a crosslinking agent, a photoinitiator and a water-soluble inorganic salt, and transferring the obtained mixed solution to the unidirectional conductive hydrogel for ultraviolet crosslinking film-forming treatment to obtain a composite conductive hydrogel. The method can achieve the differentiation of longitudinal and transverse conductivity of the composite conductive hydrogel and ensure its mechanical properties and viscosity.

Description

Technical Field

[0001] The invention belongs to the field of materials, and in particular relates to a composite 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 to at least a certain extent. To this end, one purpose of the present invention is to propose a composite conductive hydrogel and a preparation method and application thereof. The preparation method can not only realize the differentiation of longitudinal conductivity and transverse conductivity of the conductive hydrogel, but also the strength of the conductive hydrogel prepared is very good, and no additional non-woven fabric or other materials are required to increase the strength; at the same time, the prepared conductive hydrogel also has a large viscosity. When it is used in a massager, it can not only solve the installation problem at one time, but also be convenient and quick, and can also avoid the problem of difficulty in fixing or easy falling off during use, and the experience strength is also more comfortable.

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

[0005] The existing hydrogels on the market are homogeneous bodies, that is, the horizontal and vertical conductivity 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 needed to support (such as non-woven fabric) or increase the strength, or it needs to be disassembled piece by piece when in use, which is very inconvenient to operate. The inventors envision that polyvinyl alcohol and polymerized monomers can be used as film-forming substances, and the double three-dimensional network structure formed by the cross-linking polymerization of polyvinyl alcohol and the cross-linking polymerization of polymerized monomers is intertwined to form a double three-dimensional network structure to give the hydrogel material efficient water retention and excellent mechanical properties, so that no additional skeleton support is required to make up for the strength of the hydrogel material itself. However, the conductive hydrogel obtained by this method has poor viscosity and needs to be fixed to the massager body with the help of an adhesive.

[0006] To this end, according to a first aspect of the present invention, the present invention proposes a method for preparing a composite 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) performing a freezing treatment on the precursor film, 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 unidirectional conductive hydrogel;

[0011] (5) mixing the moisture retaining agent with water to obtain a third mixed solution;

[0012] (6) mixing sodium acrylate, acrylate monomer, crosslinking agent, photoinitiator, water-soluble inorganic salt and the third mixed solution and stirring to obtain a fourth mixed solution;

[0013] (7) transferring the fourth mixed solution to the unidirectional conductive hydrogel and performing a UV cross-linking film-forming treatment to form a homogeneous conductive hydrogel on the unidirectional conductive hydrogel to obtain a composite conductive hydrogel.

[0014] According to the method for preparing a composite conductive hydrogel in the above embodiment of the present invention, the inventors use a composite conductive hydrogel with a double-layer structure to simultaneously solve the problems of the longitudinal and transverse conductivity differentiation of the conductive hydrogel and the poor viscosity of the conductive hydrogel, that is, a conductive hydrogel with unidirectional conductivity advantage is pre-formed, and then a layer of unidirectional conductive viscous hydrogel is formed using it as a matrix. For unidirectional conductive hydrogels, on the one hand, polyvinyl alcohol and polymerized monomers are used as film-forming materials in the formulation system. The network structure formed by the cross-linking polymerization of polyvinyl alcohol and the network structure formed by the cross-linking polymerization of polymerized monomers are intertwined to form a double three-dimensional network structure, which gives the hydrogel material efficient water retention and excellent mechanical properties, without the need for additional skeleton support 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 direction according to a predetermined direction, thereby improving the conductivity and sensing sensitivity. Compared with the current hydrogel, which is homogeneous conductive, that is, the lateral and longitudinal conductivity are consistent, the unidirectional conductive hydrogel 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 on the side facing the skin, thereby solving the current situation that the conductive hydrogel cannot be partitioned into a single piece to achieve a multi-electrode EMS massage effect. For the isotropic conductive hydrogel, the formula system uses sodium acrylate and acrylate monomers as film-forming substances. The obtained isotropic conductive hydrogel not only has good mechanical properties, but also has high viscosity, and can be firmly combined with the unidirectional conductive hydrogel. When the composite conductive hydrogel is used in a massage device, the isotropic conductive hydrogel is in contact with the massage device body. Not only is the bonding force strong, which can prevent the conductive hydrogel from falling off, but it also does not affect the conductivity, so that the composite conductive hydrogel has the advantages of high viscosity and unidirectional conductivity.

[0015] In addition, the method for preparing a composite conductive hydrogel according to the above embodiment of the present invention may also have the following additional technical features:

[0016] In some embodiments of the present invention, the moisture humectant described in step (1) and the moisture humectant described in step (5) each independently comprises at least one of glycerol, methylpropanediol, 1,3-propylene glycol and 1,2-hexanediol.

[0017] In some embodiments of the present invention, the water described in step (1) and the water described in step (5) each independently include at least one of ultrapure water, distilled water and deionized water.

[0018] In some embodiments of the present invention, the cross-linking agent described in step (2) and the cross-linking agent described in step (6) each independently include at least one of polyamides, aliphatic amines, aromatic amines, and polyether amines.

[0019] In some embodiments of the present invention, the photoinitiator described in step (2) and the photoinitiator described in step (6) independently include at least one of the brands 2959, 1173, 907 and 184.

[0020] In some embodiments of the present invention, the water-soluble inorganic salt in step (2) and the water-soluble inorganic salt in step (6) independently include sodium chloride and / or lithium chloride.

[0021] In some embodiments of the present invention, in step (2), the polymerization monomer includes at least one of acrylamide, sodium acrylate and chitosan.

[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 in step (2) and step (6) is lithium chloride.

[0023] In some embodiments of the present invention, in step (6), the acrylic acid ester monomer includes at least one of 2-hydroxyethyl methacrylate, 2-ethoxyethyl acrylate and hydroxypropyl acrylate.

[0024] 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.

[0025] 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.

[0026] In some embodiments of the present invention, in step (2), the stirring time is 30 to 50 minutes.

[0027] 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.

[0028] In some embodiments of the present invention, 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.

[0029] In some embodiments of the present invention, the fragrance includes at least one of essence, balsam, essential oil and plant extract.

[0030] In some embodiments of the present invention, the cooling agent includes at least one of mint flavor, menthol and menthol.

[0031] In some embodiments of the present invention, step (3) includes: (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; (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.

[0032] In some embodiments of the present invention, a unidirectional conductive hydrogel with a desired thickness and shape is obtained by controlling the height and shape of the hydrogel forming area.

[0033] In some embodiments of the present invention, the height of the fixing plate located on the thermally conductive plate is greater than or equal to the thickness of the unidirectional conductive hydrogel.

[0034] In some embodiments of the present invention, in step (3), the height of the second mixed liquid in the hydrogel forming area is 0.6 to 1.2 mm, the ultraviolet cross-linking film-forming treatment is achieved by ultraviolet lamp irradiation, the ultraviolet cross-linking time is 0.5 to 2 minutes, and the ultraviolet lamp power is 0.1 to 4KW.

[0035] In some embodiments of the present invention, the fixing plate is a silicone template, and the transparent cover plate is a glass plate.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] In some embodiments of the present invention, in step (5), 2.5 to 13 parts by weight of a moisture humectant is mixed with 2 to 10 parts by weight of water.

[0041] In some embodiments of the present invention, in step (6), 1 to 5 parts by weight of sodium acrylate, 0.1 to 1 parts by weight of acrylate monomer, 0.0001 to 0.2 parts by weight of cross-linking agent, 0.00001 to 0.1 parts by weight of photoinitiator, 0.05 to 0.3 parts by weight of water-soluble inorganic salt and the third mixed solution are mixed and stirred at 20 to 80°C.

[0042] In some embodiments of the present invention, in the composite conductive hydrogel, a thickness ratio of the isotropic conductive hydrogel to the unidirectional conductive hydrogel is no greater than 1.

[0043] In some embodiments of the present invention, in the composite conductive hydrogel, a thickness ratio of the isotropic conductive hydrogel to the unidirectional conductive hydrogel is no greater than 0.8.

[0044] In some embodiments of the present invention, step (7) further includes: (7-1) defining a uniform conductive hydrogel forming area on the unidirectional conductive hydrogel using a fixing plate; (7-2) transferring the fourth mixed liquid to the uniform conductive hydrogel forming area and covering it with cellophane; (7-3) covering the cellophane with a transparent cover plate, and subjecting the fourth mixed liquid to ultraviolet radiation through the transparent cover plate and the cellophane, so that the fourth mixed liquid is cross-linked into a film, thereby forming a uniform conductive hydrogel on the unidirectional conductive hydrogel.

[0045] In some embodiments of the present invention, a homogeneous conductive hydrogel with a desired thickness and shape is formed on the unidirectional conductive hydrogel by controlling the height and shape of the homogeneous conductive hydrogel forming area.

[0046] In some embodiments of the present invention, the height of the fixing plate located on the unidirectional conductive hydrogel is the same as the thickness of the isotropic conductive hydrogel.

[0047] In some embodiments of the present invention, in step (7), 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 2-8 min, and the ultraviolet lamp power is 0.1-4 KW.

[0048] Based on the same inventive concept, according to the second aspect of the present invention, the present invention proposes a composite conductive hydrogel. According to an embodiment of the present invention, the composite conductive hydrogel comprises:

[0049] A unidirectional conductive hydrogel layer, the unidirectional conductive hydrogel layer comprising polyvinyl alcohol, a polymerizable monomer, a crosslinking agent, a photoinitiator, a water-soluble inorganic salt, a moisture humectant and water, the unidirectional conductive hydrogel having a microscopic porous structure in a thickness orientation, and the conductivity of the unidirectional conductive hydrogel in its surface orientation and thickness orientation is different;

[0050] A uniform conductive hydrogel layer, wherein the uniform conductive hydrogel layer is adhered to the unidirectional conductive hydrogel layer, the uniform conductive hydrogel comprises sodium acrylate, acrylate monomers, a crosslinking agent, a photoinitiator, a water-soluble inorganic salt, a moisture retaining agent and water, and the viscosity of the uniform conductive hydrogel layer is greater than that of the unidirectional conductive hydrogel layer.

[0051] According to the composite conductive hydrogel of the above embodiment of the present invention, regarding the unidirectional conductive hydrogel layer, 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 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. 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 a massager. When it is used in a massager, the installation problem can be solved at one time, which is convenient and fast; further, the unidirectional 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 strength; in addition, the unidirectional conductive hydrogel also has a certain viscosity, and can adhere to a variety of substrates, such as other types of hydrogels, metals, plastics, skin and other surfaces to form stable and reversible adhesion. Regarding the isotropic conductive hydrogel layer, its formula system uses sodium acrylate and acrylate monomers as film-forming substances. The obtained isotropic conductive hydrogel not only has good mechanical properties, but also has better viscosity than the unidirectional conductive hydrogel layer, and can be firmly combined with the unidirectional conductive hydrogel or other substrates. In summary, the composite conductive hydrogel has good mechanical properties, viscosity and longitudinal conductivity. When it is used in a massage device, the isotropic conductive hydrogel is in contact with the massage device body and the unidirectional conductive hydrogel is in contact with the skin. It is not only easy to install and has good firmness, but also can obtain a more comfortable experience strength.

[0052] In some embodiments of the present invention, the unidirectional conductive hydrogel layer comprises: 2 to 5 parts by weight of a moisture retaining agent, 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 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 a water-soluble inorganic salt, wherein the mass ratio of the polyvinyl alcohol to the polymerizable monomer is (0.6 to 2.4): 1; the isotropic conductive hydrogel layer comprises: 2.5 to 13 parts by weight of a moisture retaining agent, 2 to 10 parts by weight of water, 1 to 5 parts by weight of sodium acrylate, 0.1 to 1 parts by weight of an acrylate monomer, 0.0001 to 0.2 parts by weight of a cross-linking agent, 0.00001 to 0.1 parts by weight of a photoinitiator, and 0.05 to 0.3 parts by weight of a water-soluble inorganic salt.

[0053] In some embodiments of the present invention, the composite conductive hydrogel is prepared by the above-mentioned method for preparing the composite conductive hydrogel.

[0054] 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 composite conductive hydrogel adhered to the electrodes, wherein the composite conductive hydrogel includes the above-mentioned composite conductive hydrogel or a composite conductive hydrogel prepared by the above-mentioned method for preparing a composite conductive hydrogel. Compared with the prior art, the massage device is based on the advantages of unidirectional conductivity, high strength and high viscosity of the composite conductive hydrogel. It 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 strength. When it is used on a massage head with multiple electrodes in a massage device, the installation problem and the problem of easy shedding of the conductive hydrogel can be solved at one time, and the operation is convenient and quick.

[0055] In some embodiments of the present invention, the composite conductive hydrogel is adhered to the electrode through the unidirectional conductive hydrogel.

[0056] 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

[0057] 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:

[0058] Figure 1 The present invention is a flow chart of a method for preparing a unidirectional conductive hydrogel according to an embodiment of the present invention.

[0059] Figure 2 Schematic diagram of the structure of a device for performing freezing treatment according to an embodiment of the present invention.

[0060] Figure 3 Schematic diagram of unidirectional conductive hydrogel oriented crystallization according to one embodiment of the present invention.

[0061] Figure 4 Schematic diagram of the structure of a composite conductive hydrogel according to an embodiment of the present invention. DETAILED DESCRIPTION

[0062] 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.

[0063] According to the first aspect of the present invention, the present invention provides a method for preparing a composite conductive hydrogel. According to an embodiment of the present invention, the method is implemented by adopting the following inventive concept: Figure 4 The double-layer composite conductive hydrogel shown can solve the problems of the vertical and horizontal conductivity differentiation of the conductive hydrogel and the poor viscosity of the conductive hydrogel at the same time, that is, a conductive hydrogel with unidirectional conductivity is pre-formed, and then a layer of unidirectional conductive viscous hydrogel is formed with it as a matrix. When the composite conductive hydrogel is used in a massager, the unidirectional conductive hydrogel layer is in contact with the massager, and the conductive hydrogel with unidirectional conductivity is directed to the skin side. This method can not only achieve the differentiation of the longitudinal and lateral conductivity of the conductive hydrogel, but also the strength of the conductive hydrogel is very good, and no additional non-woven fabrics or other materials are required to increase the strength; at the same time, the conductive hydrogel prepared also has greater viscosity. When it is used in a massager, the installation problem can be solved at one time, which is convenient and quick, and it can also avoid the problem of difficulty in fixing or easy falling off during use, and the experience strength is also more comfortable.

[0064] According to an embodiment of the present invention, the method mainly includes two parts: one is to prepare a unidirectional conductive hydrogel (such as Figure 1 As shown), the second is to form a uniform conductive hydrogel on the unidirectional conductive hydrogel. Figures 1 to 4 The method for preparing the composite conductive hydrogel according to the above embodiment of the present invention is described in detail.

[0065] 1. Preparation of unidirectional conductive hydrogel mainly includes the following contents:

[0066] S100: Mix polyvinyl alcohol, moisture humectant and water and stir to obtain a first mixed solution

[0067] 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, one can start from the unidirectional conductive hydrogel layer and the isotropic conductive hydrogel layer respectively. For the unidirectional conductive hydrogel, 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 unidirectional conductive hydrogel with both toughness and hardness, thereby eliminating 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 unidirectional conductive hydrogel material, and the material strength is high, and no additional supporting substrate is required.

[0068] 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 unidirectional 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 to achieve the conductivity of the unidirectional conductive hydrogel; and the moisture humectant is mainly used to reduce the loss of water in the unidirectional conductive hydrogel, ensure the conductive stability of the unidirectional 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 unidirectional 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 unidirectional conductive hydrogel.

[0069] 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 mixing temperature, it is more conducive to the full dissolution of polyvinyl alcohol and improve its dissolution efficiency; and by controlling the above 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, 100,000, 120,000 or 130,000, etc. The inventors also found that the molecular weight of polyvinyl alcohol has a significant relationship with its crystallinity and the conductivity of the finally prepared conductive hydrogel. 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 strength 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 unidirectional 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 finally prepared unidirectional conductive hydrogel have a higher conductivity and a higher ratio of the longitudinal and transverse conductivity.

[0070] 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 unidirectional 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 finally prepared unidirectional conductive hydrogel at low temperatures, affect its internal crystal orientation and the conductive effect of the unidirectional conductive hydrogel, and if its dosage is too large, it will cause the surface viscosity of the unidirectional conductive hydrogel to be too small; and the moisture retaining agent is mainly used to prevent the loss of water in the unidirectional 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 unidirectional conductive hydrogel. If its dosage is too large, the entire conductive hydrogel will be The conductivity of the electrical system and the unidirectional 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 unidirectional conductive hydrogel, and the hydrogel conductivity and electrical performance experience are both poor. If the amount of water used is too much, it will unidirectionally cause the water content of the hydrogel to 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 unidirectional conductive hydrogel with expected conductivity, water retention and expected PVA crystal orientation.

[0071] 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.

[0072] According to an embodiment of the present invention, the polymerized monomer acts as a film-forming substance to provide flexibility for the unidirectional 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 unidirectional 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, without the need for an additional skeleton support to compensate for the strength of the material itself. 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.

[0073] 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 unidirectional conductive hydrogel. For example, when acrylamide, sodium acrylate or chitosan is selected to prepare the conductive hydrogel, the water retention of the obtained unidirectional conductive hydrogel is better, and when acrylamide is selected as the polymerizable monomer, the AC impedance of the obtained unidirectional 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.

[0074] 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). The above-mentioned selected in the present invention The photoinitiator of this type not only has an absorption wavelength that meets the requirements of ultraviolet lamp irradiation, but also has the advantages of low odor and / or high efficiency without yellowing. When used in a unidirectional conductive hydrogel, it is not only more conducive to generating free radicals to promote polymerization of polymerization monomers and improve film-forming properties, but also does not affect the odor and color of the hydrogel. For example, the photoinitiator with a grade 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 cross-linking agent 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 unidirectional conductive hydrogel in all directions are more uniform.

[0075] 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 unidirectional conductive hydrogel.

[0076] 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 0.020 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 proportions of polyvinyl alcohol can be 0.5, 0.8, 1.1, 1.4, 1.7 or 2, and the cross-linking agent can be 0.5 to 2. The weight proportion of can be 0.015, 0.017, 0.019, 0.021, 0.023 or 0.025, the weight proportion of photoinitiator can be 0.005, 0.008, 0.011, 0.014, 0.017 or 0.02, the weight proportion of inorganic salt can be 0.5, 0.8, 1.1, 1.4, 1.7 or 2, and the mass ratio of polyvinyl alcohol to 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 found that the solubility of polymerized monomers is usually the most difficult, while photoinitiators are easily decomposed under light of a specific wavelength. Inorganic salts are ionic compounds with good dispersibility. In the present invention, by dispersing the polymerized monomers, crosslinkers, photoinitiators and inorganic salts 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 photoinitiators. In addition, the inventors also found that if the amount of crosslinker 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 crosslinker 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 unidirectional 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 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, inflexible, and poor in 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 unidirectional conductive hydrogel finally obtained can have good film-forming properties, conductivity, water retention and mechanical properties.

[0077] 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 final unidirectional conductive hydrogel may have an expected fragrance, such as floral fragrance, fruity fragrance, etc.; by adding cooling agents, the final unidirectional conductive hydrogel may have a cool touch; by adding skin conditioning agents, the final unidirectional conductive hydrogel may have a certain skin conditioning effect.

[0078] 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 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 flavor and a certain cool touch. In addition, it should be noted that the amount of functional additives added to the unidirectional conductive hydrogel 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 unidirectional conductive hydrogel can be given a specific functional effect without significantly affecting the performance of the unidirectional conductive hydrogel itself.

[0079] S300: Performing UV cross-linking film-forming treatment on the second mixed solution to obtain a precursor film

[0080] 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. The greater the expected 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 unidirectional 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.

[0081] 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 combined with the conductive plate to control the flatness of the final unidirectional conductive hydrogel, 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 final unidirectional conductive hydrogel can be further ensured.

[0082] According to another specific embodiment of the present invention, a unidirectional conductive hydrogel of a desired thickness and shape can be obtained by controlling the height and shape of the hydrogel forming area, wherein the second mixed liquid can be made flush with or lower than the height of the hydrogel forming area, and when the second mixed liquid is flush with the height of the hydrogel forming area, the height of the fixing plate on the heat conducting plate is made the same as the thickness of the unidirectional conductive hydrogel, thereby more advantageously obtaining a unidirectional conductive hydrogel of a desired thickness; optionally, the height of the second mixed liquid can also be made lower than the height of the hydrogel forming area, even if the height of the fixing plate on the heat conducting plate is greater than the thickness of the unidirectional conductive hydrogel, thereby in subsequent operations the remaining height of the hydrogel forming area can be used to directly form a unidirectional conductive hydrogel on the unidirectional conductive hydrogel.

[0083] 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 final unidirectional conductive hydrogel. 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.

[0084] 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 freezing of the precursor film proceeds from the low temperature side to the room temperature side, and obtaining a unidirectional conductive hydrogel

[0085] 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 unidirectional 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 unidirectional conductive hydrogel. Since polyvinyl alcohol is a polymer material, after the ion channels are formed, even if the unidirectional 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.

[0086] 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 found that when the precursor film is frozen by the 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 unidirectional conductive hydrogel; and at the same freezing temperature, the longer the freezing time, the better the oriented crystallization effect of the liquid in the unidirectional conductive hydrogel. When the freezing time is extended to a certain time, continuing to extend the freezing time cannot cause further significant changes in the oriented crystallization effect of the unidirectional 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 unidirectional 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 unidirectional conductive hydrogel and ensure the freezing efficiency, thereby further improving its longitudinal conductivity.

[0087] 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 using liquid nitrogen through a heat conductive plate to allow the unidirectional conductive hydrogel to produce an excellent oriented crystallization effect.

[0088] 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 a unidirectional conductive hydrogel precursor film 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 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.

[0089] 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.

[0090] 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.

[0091] It should be noted that the "longitudinal conductivity" described in the present invention refers to the conductivity in the thickness direction of the conductive hydrogel, which is achieved by taking the thickness direction of the unidirectional 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.

[0092] 2. Forming a uniform conductive hydrogel on a unidirectional conductive hydrogel mainly includes the following contents:

[0093] S500: Mix the moisture humectant with water to obtain a third mixed solution

[0094] According to an embodiment of the present invention, by premixing the moisture retaining agent and water, the amount of water flowing in the subsequent dissolution process of sodium acrylate, acrylate monomers, crosslinking agents, photoinitiators, and inorganic salts can be avoided, ensuring that the final homogeneous conductive hydrogel has a suitable water content, thereby ensuring the conductivity of the homogeneous conductive hydrogel.

[0095] According to an embodiment of the present invention, in the process of preparing the isotropic conductive hydrogel, the mechanism of action of the water and moisture moisturizer used is the same as that of the unidirectional conductive hydrogel, which will not be described one by one here. Among them, the types of water and moisture moisturizer are not particularly limited, and those skilled in the art can choose according to actual needs. For example, the water can be at least one selected from ultrapure water, distilled water and deionized water, thereby further avoiding the negative impact of impurities or impurity ions in the water on the conductivity of the isotropic conductive hydrogel; the moisture moisturizer can be at least one selected from glycerol, methyl propanediol, 1,3-propylene glycol and 1,2-hexanediol, thereby further reducing the loss of water in the process of preparing the isotropic conductive hydrogel and improving the water retention of the isotropic conductive hydrogel.

[0096] According to a specific embodiment of the present invention, 2.5 to 13 parts by weight of a moisture retaining agent can be mixed with 2 to 10 parts by weight of water, wherein the type fraction of the moisture retaining agent can be 2.5, 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, 9.5, 10.5, 11.5, 12.5 or 13, etc., and the weight fraction of water can be 2, 3, 4, 5, 6, 7, 8, 9 or 10, etc. The inventors found that when preparing a uniform conductive hydrogel, the moisture retaining agent is mainly used to reduce the loss of water in the hydrogel. If the amount of moisture retaining agent is too small, it is difficult to achieve an obvious water retention effect and cannot effectively solve the problem of excessive water loss in the hydrogel. If the amount of moisture retaining agent is too large, the conductivity of the entire conductive system and the conductive hydrogel will deteriorate, and the moisture retaining agent will also be prone to precipitation. If the amount of water is too small, it will not only increase the difficulty of dissolving subsequent film-forming materials and raw materials such as cross-linking agents, but also limit the range of ion activity in the uniform conductive hydrogel, resulting in poor conductivity and electrical performance of the hydrogel. If the amount of water is too large, the water content of the hydrogel is too large, and the corresponding water loss rate is also faster, affecting the stability and performance of the hydrogel. In the present invention, by controlling the moisture retaining agent and water to the above relative amounts, it is more conducive to preparing a uniform conductive hydrogel with good water retention and stable conductivity.

[0097] S600: Sodium acrylate, acrylate monomer, crosslinking agent, photoinitiator, water-soluble inorganic salt and the third mixed solution are mixed and stirred to obtain a fourth mixed solution.

[0098] According to the embodiment of the present invention, sodium acrylate is used as the film-forming substance of the isotropic conductive hydrogel, and acrylate monomers are used to improve the viscosity and tensile strength of the finally prepared isotropic conductive hydrogel, thereby further solving the problem of poor mechanical properties and low viscosity of the conductive hydrogel. Among them, the cross-linking agent is used to cross-link and polymerize the linear polymer to form a three-dimensional network structure that is entangled with each other, thereby improving the mechanical properties and strength of the isotropic conductive hydrogel; the photoinitiator is used to generate free radicals to initiate the polymerization of sodium acrylate and acrylate monomers to promote film formation; and the inorganic salt is used to provide conductive ions.

[0099] According to a specific embodiment of the present invention, in the process of preparing the isotropic conductive hydrogel, the mechanism of action of the inorganic salt, crosslinking agent and photoinitiator used is the same as that of the unidirectional conductive hydrogel, which will not be described one by one here. Among them, the types of inorganic salts, crosslinking agents and photoinitiators are not particularly limited, and those skilled in the art can select them 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 found that lithium chloride not only has better conductivity, but also does not affect the solubility of the polymerizable monomer sodium acrylate, thereby further ensuring the conductive properties and film-forming properties of the isotropic conductive hydrogel; for another example, the crosslinking agent can be at least one selected from polyamides, aliphatic amines, aromatic amines and polyether amines. The use of the above-mentioned types of crosslinking agents is more conducive to promoting the crosslinking polymerization of linear polymers and forming uniform The stable double three-dimensional network structure makes the mechanical properties and strength of the isotropic conductive hydrogel more uniform in all directions; for another example, 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). The above-mentioned types of photoinitiators not only have absorption wavelengths that meet the requirements of ultraviolet light irradiation, but also have the advantages of low odor and / or high efficiency without yellowing. When used in the isotropic conductive hydrogel, it is not only more conducive to generating free radicals to promote the polymerization of sodium acrylate and acrylate monomers, improve film-forming properties, but also does not affect the odor and color of the hydrogel.

[0100] According to another specific embodiment of the present invention, the type of acrylate monomers in the present invention is not particularly limited, and those skilled in the art can select according to actual needs. For example, the acrylate monomers can include at least one of 2-hydroxyethyl methacrylate, 2-ethoxyethyl acrylate and hydroxypropyl acrylate, which can be more conducive to improving the viscosity and tensile strength of the isotropic conductive hydrogel. Therefore, on the one hand, there is no need for additional non-woven fabrics or other materials to increase the strength of the isotropic conductive hydrogel, and on the other hand, the isotropic conductive hydrogel can also have a certain flexibility.

[0101] According to another specific embodiment of the present invention, 1 to 5 parts by weight of sodium acrylate, 0.1 to 1 parts by weight of acrylate monomer, 0.0001 to 0.2 parts by weight of crosslinking agent, 0.00001 to 0.1 parts by weight of photoinitiator, 0.05 to 0.3 parts by weight of water-soluble inorganic salt and the third mixed solution can be mixed and stirred at 20 to 80° C. For example, the weight parts of sodium acrylate can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5, the weight parts of acrylate monomer can be 0.1, 0.3, 0.5, 0.7, 0.9 or 1, and the weight parts of crosslinking agent can be 0.005, 0.01, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18 or 0.20. The weight proportion of the photoinitiator can be 0.00005, 0.0001, 0.0005, 0.001, 0.005, 0.01, 0.015, 0.02, 0.05, 0.08 or 0.1, etc., and the weight proportion of the inorganic salt can be 0.05, 0.1, 0.12, 0.15, 0.18, 0.2, 0.24, 0.28 or 0.3, etc. The inventors have found that, for a moisturizing agent solution composed of 2.5 to 13 parts by weight of a moisture-moisturizing agent and 2 to 10 parts by weight of water, if the content of sodium acrylate is too little, it is not only not conducive to film formation, but also equivalent to an excess of moisture-moisturizing agent and water, which will have an adverse effect on the conductivity and water loss rate of the isotropic conductive hydrogel and easily lead to the precipitation of the moisture-moisturizing agent. If the content of sodium acrylate is too much, the water retention and conductivity of the isotropic conductive hydrogel will decrease. If the mass ratio of sodium acrylate to acrylate monomers is too large, the effect on improving the viscosity and tensile strength of the isotropic conductive hydrogel is not obvious. If the mass ratio of sodium acrylate to acrylate monomers is too small, although excellent viscosity can be obtained, the isotropic conductive hydrogel will be too soft and prone to drawing, which is not conducive to the later addition. The use of conductive hydrogel; if the amount of cross-linking agent is too much, it will lead to excessive cross-linking, the density of the formed three-dimensional network structure is too large, the hydrogel system is too hard, and the touch is affected. If the cross-linking agent is too little, the three-dimensional network formed will be incomplete, the hydrogel mechanical properties will be poor, 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 be less, and the polymer formed by the monomer will be less, which is not conducive to improving the strength and polymerization degree of the isotropic conductive hydrogel; if the amount of inorganic salt is too little, it will affect the macroscopic conductivity, and with the increase of the amount of inorganic salt, although the conductivity of the hydrogel can be improved, if the amount of inorganic salt is too high, it will not only affect the solubility of the polymerized monomer sodium acrylate, resulting in a decrease in the polymerization degree of the monomer, but also increase the cost of raw materials. In the present invention, by controlling each raw material component to the above ratio, the finally obtained isotropic conductive hydrogel can have good film-forming property, conductivity, water retention, viscosity and tensile strength.

[0102] According to an embodiment of the present invention, a functional additive may be further added to the fourth mixed solution, wherein the functional additive may include at least one of a fragrance, a cooling agent, and a skin conditioning agent. It should be noted that the types and effects of the fragrance, cooling agent, and skin conditioning agent used in the uniform conductive hydrogel are the same as those of the unidirectional conductive hydrogel, and will not be described one by one here. Thus, the uniform conductive hydrogel can also have at least one of the expected fragrance, cool touch, and skin conditioning effects, so that even if the uniform conductive hydrogel is in contact with the skin, it can achieve a good touch or conditioning effect. In addition, it should be noted that the amount of the functional additive used in the uniform conductive hydrogel is not particularly limited, and those skilled in the art can select it according to actual needs. For example, the amount of the cooling agent added may not be greater than 0.1wt% of the uniform conductive hydrogel, and the amount of the fragrance added may not be greater than 0.1wt% or 0.1mL of the uniform conductive hydrogel, etc., thereby giving the conductive hydrogel a specific functional effect without significantly affecting the performance of the conductive hydrogel itself.

[0103] S700: transferring the fourth mixed solution to the unidirectional conductive hydrogel and performing UV cross-linking film-forming treatment to form a homogeneous conductive hydrogel on the unidirectional conductive hydrogel to obtain a composite conductive hydrogel

[0104] According to an embodiment of the present invention, the ultraviolet cross-linking film-forming treatment of the fourth mixed liquid can be achieved by ultraviolet lamp irradiation. For the raw material composition and ratio of the isotropic conductive hydrogel in the present invention, when the film thickness is 0.6-1.2 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, the ultraviolet cross-linking time can be 2-8 min, for example, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min or 8 min, and the ultraviolet lamp power can be 0.1-4 KW, for example, 0.1 KW, 0.5 KW, 1 KW, 1.5 KW, 2 KW, 2.5 KW, 3 KW, 3.5 KW. W or 4KW, etc. The inventors found that for the raw material ratio of the isotropic conductive hydrogel of the present invention, the UV cross-linking time and the UV irradiation power will affect the cross-linking degree. Under the same film thickness, the smaller the UV irradiation power, the longer the required UV cross-linking time. 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 isotropic conductive hydrogel to be too hard and affect the touch of the conductive hydrogel. Based on the isotropic conductive hydrogel 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 of the fourth mixed liquid, but also avoid the problem of excessive cross-linking.

[0105] According to a specific embodiment of the present invention, in the composite conductive hydrogel, the thickness ratio of the isotropic conductive hydrogel to the unidirectional conductive hydrogel may be no greater than 1, for example, it may be 0.2, 0.4, 0.6, 0.8 or 1, etc. The inventors found that the viscosity of the unidirectional conductive hydrogel is poor. If the thickness of the isotropic conductive hydrogel is too thin, it will not have a good adhesion effect, which is not conducive to the stable combination of the two and the fixation of the composite conductive hydrogel to a specific device. If the thickness of the isotropic conductive hydrogel is too thick, it will affect the longitudinal guidance rate of the entire composite conductive hydrogel. In the present invention, by controlling the thickness ratio of the isotropic conductive hydrogel to the unidirectional conductive hydrogel to the above range, the composite conductive hydrogel can have both good viscosity and longitudinal guidance. Preferably, the thickness ratio of the isotropic conductive hydrogel to the unidirectional conductive hydrogel in the composite conductive hydrogel may be no greater than 0.8, thereby further ensuring that the composite conductive hydrogel has good longitudinal conductivity.

[0106] According to another specific embodiment of the present invention, transferring the fourth mixed liquid to the unidirectional conductive hydrogel and performing ultraviolet cross-linking film-forming treatment may further include: using a fixing plate to define a uniform conductive hydrogel forming area on the unidirectional conductive hydrogel; transferring the fourth mixed liquid to the uniform conductive hydrogel forming area and covering it with cellophane; covering the cellophane with a transparent cover plate, and ultraviolet irradiating the fourth mixed liquid through the transparent cover plate and the cellophane, so as to cross-link the fourth mixed liquid to form a film, and form a uniform conductive hydrogel on the unidirectional conductive hydrogel. This can further ensure the flatness and uniformity of the final composite conductive hydrogel.

[0107] According to another specific embodiment of the present invention, a homogeneous conductive hydrogel of expected thickness and shape can be formed on the unidirectional conductive hydrogel by controlling the height and shape of the homogeneous conductive hydrogel forming area, which is more conducive to controlling the thickness ratio of the homogeneous conductive hydrogel and the unidirectional conductive hydrogel; preferably, the fourth mixed liquid can be flush with the height of the homogeneous conductive hydrogel forming area, even if the height of the fixed plate located on the unidirectional conductive hydrogel is the same as the thickness of the homogeneous conductive hydrogel, which can more advantageously obtain a composite conductive hydrogel with an expected thickness ratio. It should be noted that the materials of the fixed plate and the transparent cover plate in this process are not particularly limited, and those skilled in the art can choose according to actual needs. For example, the fixed plate can be a silicone template, and the transparent cover plate can be a glass plate.

[0108] In summary, according to the method for preparing a composite conductive hydrogel according to the above embodiment of the present invention, the inventors use a composite conductive hydrogel with a double-layer structure to simultaneously solve the problems of the longitudinal and transverse conductivity differentiation of the conductive hydrogel and the poor viscosity of the conductive hydrogel, that is, a conductive hydrogel with unidirectional conductivity advantage is pre-formed, and then a layer of unidirectional conductive viscous hydrogel is formed using it as a matrix. For unidirectional conductive hydrogels, on the one hand, polyvinyl alcohol and polymerized monomers are used as film-forming materials in the formulation system. The network structure formed by the cross-linking polymerization of polyvinyl alcohol and the network structure formed by the cross-linking polymerization of polymerized monomers are intertwined to form a double three-dimensional network structure, which gives the hydrogel material efficient water retention and excellent mechanical properties, without the need for additional skeleton support 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 direction according to a predetermined direction, thereby improving the conductivity and sensing sensitivity. Compared with the current hydrogel, which is homogeneous conductive, that is, the lateral and longitudinal conductivity are consistent, the unidirectional conductive hydrogel 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 on the side facing the skin, thereby solving the current situation that the conductive hydrogel cannot be partitioned into a single piece to achieve a multi-electrode EMS massage effect. For the isotropic conductive hydrogel, the formula system uses sodium acrylate and acrylate monomers as film-forming substances. The obtained isotropic conductive hydrogel not only has good mechanical properties, but also has high viscosity, and can be firmly combined with the unidirectional conductive hydrogel. When the composite conductive hydrogel is used in a massage device, the isotropic conductive hydrogel is in contact with the massage device body. Not only is the bonding force strong, it can prevent the conductive hydrogel from falling off, but also does not affect the conductivity, so that the composite conductive hydrogel has the advantages of high viscosity and unidirectional conductivity. Therefore, the preparation method can not only realize 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 fabrics or other materials are required to increase the strength; at the same time, the conductive hydrogel prepared also has high viscosity. When it is used in a massager, it can not only solve the installation problem at one time, but also be convenient and quick, and can also avoid the problem of difficulty in fixing or easy falling off during use, and the experience strength is also more comfortable.

[0109] According to the second aspect of the present invention, the present invention proposes a composite conductive hydrogel. According to an embodiment of the present invention, the composite conductive hydrogel includes: a unidirectional conductive hydrogel layer and a homogeneous conductive hydrogel layer. Among them, the unidirectional conductive hydrogel layer includes polyvinyl alcohol, a polymerized monomer, a crosslinking agent, a photoinitiator, a water-soluble inorganic salt, a moisture humectant and water, the unidirectional conductive hydrogel has a microscopic porous structure in the thickness orientation, and the conductivity of the unidirectional conductive hydrogel in its surface orientation and thickness orientation is different; the homogeneous conductive hydrogel layer adheres to the unidirectional conductive hydrogel layer, the homogeneous conductive hydrogel includes sodium acrylate, an acrylate monomer, a crosslinking agent, a photoinitiator, a water-soluble inorganic salt, a moisture humectant and water, and the viscosity of the homogeneous conductive hydrogel layer is greater than that of the unidirectional conductive hydrogel layer. The composite conductive hydrogel has good mechanical properties, viscosity and longitudinal conductivity. When it is used in a massage device, the homogeneous conductive hydrogel contacts the massage device body and the unidirectional conductive hydrogel contacts the skin. It is not only easy to install and has good firmness, but also can obtain a more comfortable experience strength.

[0110] According to the composite conductive hydrogel of the above embodiment of the present invention, regarding the unidirectional conductive hydrogel layer, 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 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. 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 a massager. When it is used in a massager, the installation problem can be solved at one time, which is convenient and fast; further, the unidirectional 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 strength; in addition, the unidirectional conductive hydrogel also has a certain viscosity, and can adhere to a variety of substrates, such as other types of hydrogels, metals, plastics, skin and other surfaces to form stable and reversible adhesion. Regarding the isotropic conductive hydrogel layer, its formula system uses sodium acrylate and acrylate monomers as film-forming substances. The obtained isotropic conductive hydrogel not only has good mechanical properties, but also has better viscosity than the unidirectional conductive hydrogel layer, and can be firmly combined with the unidirectional conductive hydrogel or other substrates. In summary, the composite conductive hydrogel has good mechanical properties, viscosity and longitudinal conductivity. When it is used in a massage device, the isotropic conductive hydrogel is in contact with the massage device body and the unidirectional conductive hydrogel is in contact with the skin. It is not only easy to install and has good firmness, but also can obtain a more comfortable experience. It should be noted that the inventive concept of the composite conductive hydrogel is the same as the above-mentioned method for preparing the composite conductive hydrogel. The characteristics and effects described for the above-mentioned method for preparing the composite conductive hydrogel are also applicable to the composite conductive hydrogel, and will not be repeated here.

[0111] It should be noted that the microporous structure of the unidirectional 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 unidirectional conductive 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 unidirectional conductive hydrogel and does not affect the flatness of the surface of the unidirectional conductive hydrogel.

[0112] According to a specific embodiment of the present invention, the unidirectional conductive hydrogel layer includes: 2 to 5 parts by weight of a moisture retaining agent, 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 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 a water-soluble inorganic salt, and the mass ratio of polyvinyl alcohol to the polymerizable monomer is (0.6 to 2.4): 1; the isotropic conductive hydrogel layer includes: 2.5 to 13 parts by weight of a moisture retaining agent, 2 to 10 parts by weight of water, 1 to 5 parts by weight of sodium acrylate, 0.1 to 1 parts by weight of an acrylate monomer, 0.0001 to 0.2 parts by weight of a cross-linking agent, 0.00001 to 0.1 parts by weight of a photoinitiator and 0.05 to 0.3 parts by weight of a water-soluble inorganic salt. In the present invention, by controlling the composite conductive hydrogel to be composed of the above-mentioned raw materials, it can be further ensured that the composite conductive hydrogel has good longitudinal conductivity, which is significantly different from the transverse conductivity, and has good 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. At the same time, it has greater viscosity. When it is used in a massager, the installation problem and the problem of easy shedding of the conductive hydrogel can be solved at one time. It is not only convenient and quick, but also more comfortable to experience.

[0113] According to another specific embodiment of the present invention, the composite conductive hydrogel is prepared by the above-mentioned method for preparing the composite conductive hydrogel, which can further facilitate obtaining a conductive hydrogel having excellent properties such as good longitudinal conductivity, mechanical strength, viscosity, and water retention.

[0114] 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, an electrode arranged on the massage device body, and a conductive hydrogel adhered to the electrode, wherein the conductive hydrogel includes the above-mentioned composite conductive hydrogel or a composite conductive hydrogel prepared by the above-mentioned method for preparing a composite conductive hydrogel. Compared with the prior art, the massage device is based on the advantages of unidirectional conductivity, high strength and high viscosity of the composite 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 and the problem that the conductive hydrogel is easy to fall off 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 composite conductive hydrogel and the method for preparing the composite conductive hydrogel are also applicable to the massage device, and will not be repeated here one by one.

[0115] According to a specific embodiment of the present invention, the composite conductive hydrogel in the massage device can be adhered to the electrode of the massage device through the isotropic conductive hydrogel. Considering that in the composite conductive hydrogel, the unidirectional conductive hydrogel has better longitudinal conductivity, while the isotropic conductive hydrogel has greater viscosity, a more comfortable experience can be provided by directly contacting the unidirectional conductive hydrogel with the skin. By adhering the isotropic conductive hydrogel to the electrode of the massage device, the bonding strength between the composite conductive hydrogel and the electrode can be improved to prevent it from falling off during use.

[0116] 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.

[0117] General approach

[0118] The method for preparing a composite 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 the 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 it, and ultraviolet crosslinking for 0.5-2 mi n, the power of the UV lamp is 0.1~4KW; 5) Move the fixing clip as far as possible to the middle, fill the Dewar flask with liquid nitrogen, place the heat conducting plate downward and the cover plate upward on the Dewar flask, and freeze for 3~10 minutes; in this way, the temperature of the side close to the heat conducting plate is -80℃~-200℃, and the other side is at room temperature, so that the liquid freezes from bottom to top to form corresponding icicles; 6) After mixing the moisture moisturizer with water, add sodium acrylate, acrylate monomer, crosslinking agent, photoinitiator and inorganic salt in turn, stir and dissolve at 20~80℃, and then add additives; 7) Put (silicone template) on the unidirectional conductive hydrogel (glass plate when evaluating the unidirectional conductive layer separately), evenly apply the solution obtained in step 6), cover with a layer of cellophane, and then cover with a transparent cover plate without clamping, UV crosslink for 2~8min, power 0.1~4KW.

[0119] 1. Preparation of unidirectional conductive hydrogel and evaluation of its performance

[0120] Please refer to Example 1.1, Example 1.2 and Comparative Example 1.1 and Comparative Example 1.2 for details.

[0121] The raw material ratios and evaluation results of Example 1.1, Example 1.2, and Comparative Examples 1.1 and 1.2 are shown in Table 1. The controlled process parameters are the same. In step 1), the polyvinyl alcohol dissolution temperature is 90°C, the stirring time is 2h, and the average molecular weight of polyvinyl alcohol is 77000; in step 2), the stirring and dissolving time is 40min; in step 4), the ultraviolet crosslinking time 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 unidirectional conductive hydrogel is 1mm. Among them, the experience strength is tested by using the obtained conductive hydrogel in a massager.

[0122] It can be seen from Example 1.1, Example 1.2, Comparative Example 1.1 and Comparative Example 1.2 that the mass ratio of polyvinyl alcohol to polymerized monomer is too large or too small, which 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. In fact, the mass ratio of polyvinyl alcohol to polymerized monomer has a significant effect on the water retention, AC impedance, conductivity, mechanical properties and experience strength of the conductive hydrogel. With the increase of the mass ratio of polyvinyl alcohol to polymerized monomer, 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. The mass ratio of polyvinyl alcohol to polymerized monomer is too large, which will cause the overall performance of the hydrogel material to be hard, without flexibility, and poor water retention; and the mass ratio of polyvinyl alcohol to polymerized monomer is too small, although the hydrogel material has excellent tensile strength, it is not conducive to forming an oriented conductive channel 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 monomer is controlled to be greater than 1 / 3 and less than 1 / 0.4 is better.

[0123] Table 1 Comparison of raw material ratios and evaluation results of unidirectional conductive hydrogels

[0124]

[0125]

[0126] 2. Preparation of uniformly conductive hydrogels and evaluation of their properties

[0127] Please refer to Examples 2.1 to 2.5 and Comparative Examples 2.1 to 2.2 for details.

[0128] The raw material ratios and evaluation results of Examples 2.1 to 2.5 and Comparative Examples 2.1 to 2.2 are shown in Table 2. The controlled process parameter conditions are the same. In step 6), the dissolution temperature is 60° C.; in step 7), the UV cross-linking time is 4 min, the UV lamp power is 0.2 KW, and the thickness of the obtained isotropic conductive hydrogel is 1 mm.

[0129] It can be seen from Examples 2.1 to 2.5 and Comparative Examples 2.1 to 2.2 that under the same conditions, as the mass ratio of moisturizer to pure water decreases, the crosslinking resistance of the conductive hydrogel decreases, and the surface viscosity decreases first and then increases; in addition, the mass ratio of sodium acrylate to acrylate has a significant effect on the tensile strength, viscosity and crosslinking resistance of the conductive hydrogel. In fact, as the mass ratio of sodium acrylate to acrylate decreases, the surface viscosity of the conductive hydrogel gradually increases as a whole. In addition, when the total amount of sodium acrylate and hydroxyethyl acrylate increases, the amount of crosslinker and photoinitiator required also increases. In actual operation, in Comparative Example 2.1, when the weight ratio of sodium acrylate to hydroxyethyl acrylate is greater than 2.2 times, the material has poor processing performance, is very soft, and is difficult to form.

[0130] Table 2 Comparison of raw material ratios and evaluation results of uniformly conductive hydrogels

[0131]

[0132]

[0133] 3. Preparation of composite conductive hydrogels and evaluation of their properties

[0134] Please refer to Examples 3.1 to 3.4 and Comparative Examples 3.1 to 3.2 for details.

[0135] The raw material ratios, controlled process parameters and evaluation results of Examples 3.1 to 3.4 and Comparative Examples 3.1 to 3.2 are shown in Table 3.

[0136] From Table 3, it can be seen that under the same conditions, the thickness ratio of the isotropic conductive hydrogel and the unidirectional conductive hydrogel will significantly affect the longitudinal and transverse conductivity ratio of the composite conductive hydrogel and the bonding strength between the composite conductive hydrogel and the substrate. When the thickness ratio of the isotropic conductive hydrogel and the unidirectional conductive hydrogel is not greater than 1, the longitudinal and transverse conductivity ratio of the composite conductive hydrogel is larger, and the experience of using it in the massager is better.

[0137] Table 3 Comparison of raw material ratios and evaluation results of composite conductive hydrogels

[0138]

[0139]

[0140] 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.

[0141] 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 composite 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) freezing the precursor film, wherein one side of the precursor film is kept at room temperature and the other side is kept at low temperature during the freezing process, 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 unidirectional conductive hydrogel; (5) mixing the moisture retaining agent with water to obtain a third mixed solution; (6) mixing sodium acrylate, acrylate monomer, crosslinking agent, photoinitiator, water-soluble inorganic salt and the third mixed solution and stirring to obtain a fourth mixed solution; (7) transferring the fourth mixed solution to the unidirectional conductive hydrogel and performing a UV cross-linking film-forming treatment to form a homogeneous conductive hydrogel on the unidirectional conductive hydrogel to obtain a composite 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; In step (6), the acrylic acid ester monomer includes at least one of 2-hydroxyethyl methacrylate, 2-ethoxyethyl acrylate and hydroxypropyl acrylate.

2. The method according to claim 1, characterized in that The moisture humectant described in step (1) and the moisture humectant described in step (5) independently include 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 The water in step (1) and the water in step (5) each independently include at least one of ultrapure water, distilled water and deionized water.

4. The method according to claim 1, characterized in that: The cross-linking agent described in step (2) and the cross-linking agent described in step (6) each independently comprises at least one of polyamides, aliphatic amines, aromatic amines, and polyether amines.

5. The method according to claim 1, characterized in that The photoinitiator described in step (2) and the photoinitiator described in step (6) independently include at least one of the brands 2959, 1173, 907 and 184.

6. The method according to claim 1, characterized in that The water-soluble inorganic salt in step (2) and the water-soluble inorganic salt in step (6) independently include sodium chloride and / or lithium chloride.

7. 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.

8. 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.

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) 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 unidirectional 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 greater than or equal to the thickness of the unidirectional conductive hydrogel.

17. The method according to claim 16, characterized in that In step (3), the height of the second mixed liquid in the hydrogel forming area 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 15, 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 15, 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 15, 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 In step (5), 2.5 to 13 parts by weight of a moisture humectant is mixed with 2 to 10 parts by weight of water.

23. The method according to claim 22, characterized in that In step (6), 1 to 5 parts by weight of sodium acrylate, 0.1 to 1 parts by weight of acrylate monomer, 0.0001 to 0.2 parts by weight of cross-linking agent, 0.00001 to 0.1 parts by weight of photoinitiator, 0.05 to 0.3 parts by weight of water-soluble inorganic salt and the third mixed solution are mixed and stirred at 20 to 80°C.

24. The method according to claim 1, characterized in that In the composite conductive hydrogel, a thickness ratio of the isotropic conductive hydrogel to the unidirectional conductive hydrogel is no greater than 1.

25. The method according to claim 1, characterized in that In the composite conductive hydrogel, a thickness ratio of the isotropic conductive hydrogel to the unidirectional conductive hydrogel is no greater than 0.

8.

26. The method according to claim 1, characterized in that Step (7) further includes: (7-1) defining a uniform conductive hydrogel forming area on the unidirectional conductive hydrogel using a fixing plate; (7-2) transferring the fourth mixed solution to the uniformly conductive hydrogel forming area and covering it with cellophane; (7-3) Covering the cellophane with a transparent cover plate, and irradiating the fourth mixed solution with ultraviolet light through the transparent cover plate and the cellophane so as to cross-link the fourth mixed solution into a film, thereby forming a homogeneous conductive hydrogel on the unidirectional conductive hydrogel.

27. The method according to claim 26, characterized in that A homogeneous conductive hydrogel with a desired thickness and shape is formed on the unidirectional conductive hydrogel by controlling the height and shape of the homogeneous conductive hydrogel forming area.

28. The method according to claim 26, characterized in that The height of the fixing plate located on the unidirectional conductive hydrogel is the same as the thickness of the isotropic conductive hydrogel.

29. The method according to claim 28, characterized in that In step (7), 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 2-8 min, and the power of the ultraviolet lamp is 0.1-4 kW.

30. A composite conductive hydrogel prepared by the method according to any one of claims 1 to 29, characterized in that: include: A unidirectional conductive hydrogel layer, wherein the unidirectional conductive hydrogel layer comprises polyvinyl alcohol, a polymerizable monomer, a crosslinking agent, a photoinitiator, a water-soluble inorganic salt, a moisture humectant and water, wherein the unidirectional conductive hydrogel has a microscopic porous structure in a thickness orientation, and the conductivity of the unidirectional conductive hydrogel in its surface orientation and thickness orientation is different; a uniform conductive hydrogel layer, wherein the uniform conductive hydrogel layer is adhered to the unidirectional conductive hydrogel layer, the uniform conductive hydrogel comprises sodium acrylate, acrylate monomers, a crosslinking agent, a photoinitiator, a water-soluble inorganic salt, a moisture humectant and water, and the viscosity of the uniform conductive hydrogel layer is greater than that of the unidirectional conductive hydrogel layer, The mass ratio of the polyvinyl alcohol to the polymerization monomer is (0.6-1.5):

1.

31. The composite conductive hydrogel according to claim 30, characterized in that: The unidirectional conductive hydrogel layer 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 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 a water-soluble inorganic salt; The isotropic conductive hydrogel layer comprises: 2.5 to 13 parts by weight of a moisture retaining agent, 2 to 10 parts by weight of water, 1 to 5 parts by weight of sodium acrylate, 0.1 to 1 parts by weight of an acrylate monomer, 0.0001 to 0.2 parts by weight of a cross-linking agent, 0.00001 to 0.1 parts by weight of a photoinitiator, and 0.05 to 0.3 parts by weight of a water-soluble inorganic salt.

32. A massage device, characterized in that: The invention comprises a massage device body, an electrode arranged on the massage device body and a composite conductive hydrogel adhered to the electrode, wherein the composite conductive hydrogel comprises the composite conductive hydrogel described in any one of claims 30 to 31 or a composite conductive hydrogel prepared by the method described in any one of claims 1 to 29.

33. The massage device according to claim 32, characterized in that The composite conductive hydrogel is adhered to the electrode through the conductive hydrogel.

Images