Multistage pore conductive gel, preparation method thereof and friction nano generator

Abstract

The invention particularly relates to hierarchical porous conductive gel, a preparation method thereof and a friction nano-generator. Aiming at the defects of mechanical property and electric conductivity of the existing conductive gel material, the invention provides the conductive gel with a multi-stage pore structure, food-grade raw materials are adopted, and the multi-stage pore structure is realized through a freeze-drying method and an interactive embedding mode of gel with different densities; the moist environment of an internal ion solution can be kept for a long time, and good stability and flexibility are achieved. The invention also provides a friction nano-generator using the gel material as a conductive medium, and the friction nano-generator has good electrical properties and good application prospects when applied to wearable electronic equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of conductive gels, and in particular relates to a multi-level porous conductive gel with long-term stability, high conductivity and good mechanical properties, a preparation method of the conductive gel and a friction nanogenerator using the conductive gel. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] With the growing demand for environmental protection and sustainable development, gel, a natural, polymeric material, has become a key material in numerous fields due to its excellent biodegradability, biocompatibility, and adaptability. In industries such as medicine, food packaging, electronic equipment, and sensors, gels are widely used in wound dressings, biodegradable packaging, intelligent soft robotics, and environmental monitoring. In particular, in triboelectric nanogenerator technology, gels are considered a core functional material due to their unique advantages, including high flexibility and stretchability. These properties hold great promise for their application in wearable devices, offering new possibilities for the development of flexible electronic nanoenergy devices.

[0004] However, most gel materials currently used in triboelectric nanogenerators (TGNs) suffer from poor safety, stability, conductivity, and mechanical properties. These issues have limited their application in TGNs. For example, many gels use toxic monomers, initiators, or crosslinkers during their preparation. These chemical residues can cause environmental and physiological toxicity, posing a significant safety hazard in wearable devices. Furthermore, conventional gels are prone to dehydration and drying, significantly reducing their conductivity and compromising the long-term stability of TGNs. Furthermore, conventionally prepared gels exhibit low conductivity, making efficient charge transfer difficult. Finally, due to their low mechanical strength, they are susceptible to structural damage under long-term stress, significantly limiting their application in TGNs. Therefore, there is an urgent need to develop gel materials with high safety, long-term stability, high conductivity, and excellent mechanical properties to meet the practical needs of TGN technology and promote the commercialization and large-scale application of this emerging energy technology. Summary of the Invention

[0005] In response to the shortcomings of the prior art, the present invention aims to provide a conductive gel material that combines high safety, long-term stability, high conductivity, and excellent mechanical properties. To achieve this technical objective, the present invention employs a method for creating a multi-pore structure by distributing gel precursors of varying densities during the gel preparation process. This improves the gel material's ability to retain ionic solutions, ultimately providing a conductive gel material with excellent mechanical strength, flexibility, and stability. This material can be widely used in a variety of fields, including triboelectric nanogenerators, wearable devices, food packaging, and toys.

[0006] Based on the above technical effects, the present invention provides the following technical solutions: In a first aspect, a method for preparing a multi-level porous conductive gel is provided, comprising the following steps: (1) The base polymer, antibacterial agent, pH regulator, chelating agent and moisturizing agent were mixed in a mass ratio of 1: 0.07-0.38: 0.04-0.19: 0.11-0.25: 0.07-0.18: 13.57-26.25, and water was added and stirred at room temperature for 0.5-3 h. The mixture was further stirred in a water bath at 35-50 °C for 0.2-3 h. The pore-forming agent was then added and stirred quickly. The mixture was heated to 70-80 °C and kept warm for 0.1-0.5 h to obtain a primary gel, which was then freeze-dried to obtain the first gel. (2) Add water to the base polymer, antibacterial agent, pH regulator, chelating agent and moisturizing agent and stir in a water bath at 40-60°C for 0.2-3h. After raising the temperature to 70-85°C, add the thickener and defoaming agent and continue stirring for 0.2-2h to obtain a second gel; the mass ratio of the base polymer, antibacterial agent, pH regulator, chelating agent, moisturizing agent, thickener and defoaming agent is 1: 0.07-0.38: 0.04-0.19: 0.11-0.25: 0.07-0.18: 6.43-13.75: 0.01-0.13: 0.007-0.05; (3) In a closed space, slowly add the second gel at a temperature of 70-85°C to the first gel, maintain the ambient vacuum at 15-20 kPa to allow the second gel to completely penetrate the first gel to obtain a composite gel, and freeze-dry to obtain a gel complex; (4) Immerse the gel complex in a 0.05-1 mol / L salt or ion solution, treat it at a vacuum of 10-15 kPa and room temperature for 10-30 min, and stir it magnetically at 100-200 rpm to obtain a multi-level porous conductive gel.

[0007] In the above step (1), there are the following preferred technical solutions: The matrix polymer includes but is not limited to one or more of hydroxypropyl methylcellulose, chitosan, sodium hyaluronate, gelatin, xanthan gum, sodium alginate, pectin, casein, and soy protein mixed in any proportion.

[0008] The antibacterial agent is any one of potassium sorbate, tea tree oil, garlic extract, mint oil, rosemary extract, turmeric extract, lauryl alcohol, citric acid, lactic acid, and hydrochloride.

[0009] The pH regulator is any one of citric acid, lactic acid, sodium citrate, sodium acetate, and sodium bicarbonate.

[0010] The complexing agent is any one of citric acid, sodium gluconate, tannic acid and gluconic acid.

[0011] The moisturizing agent is any one of glycerin, hyaluronic acid, panthenol, trehalose, squalene and shea butter.

[0012] The pore-forming agent is any one of ammonium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, zinc carbonate, ammonium nitrate, and ammonium nitrite.

[0013] The mass ratio of the pore-forming agent to the matrix polymer is 1:8-35.

[0014] After adding the pore-forming agent, microwave heating is preferably used to promote thermal decomposition of the pore-forming agent, with the power of the microwave being 100-600W.

[0015] The primary gel is washed with deionized water multiple times until no residual pore-forming agent components are detected in the washing solution; after washing, it is naturally dried at room temperature and then freeze-dried. The freeze-drying procedure is as follows: freezing (-40~-20°C, 5.5~6.5h), heating (-20~-10°C, 2~4h), sublimation (-10~0°C, vacuum degree of 5~10Pa, 12~24h) and post-drying (25~30°C, 2~4h).

[0016] In the above step (2), there are the following preferred technical solutions: The matrix polymer, antibacterial agent, pH regulator, chelating agent, and moisturizing agent are within the same defined ranges as those in step (1). However, each of the above components in the first gel and the second gel can be selected independently, and it is not required that each type of component in the two gels must be completely consistent. Taking the matrix polymer as an example, in one feasible embodiment, hydroxypropyl methylcellulose is used in the first gel and chitosan is used in the second gel.

[0017] The thickener is any one of carbomer, xanthan gum, gelatin, modified starch, methyl cellulose, low methoxyl pectin, gum arabic and pectin.

[0018] The defoaming agent is any one of olive oil, rapeseed oil, coconut oil, dimethyl silicone oil, saponin, lecithin, calcium chloride, and sodium bicarbonate.

[0019] In the above step (3), there are the following preferred technical solutions: The freeze-drying procedure is as follows: freezing (-40~-20°C, 5.5~6.5h), heating (-20~-10°C, 2~4h), sublimation (-10~0°C, vacuum degree of 5~10Pa, 12~24h) and post-drying (25~30°C, 2~4h).

[0020] The above step (4) also has the following preferred technical solution: The salt or ion solution is any one of aqueous solutions of sodium citrate, sodium lactate, sodium malate, sodium chloride, potassium chloride, magnesium chloride, and sodium bicarbonate.

[0021] The second aspect of the present invention provides a multi-level porous conductive gel prepared by the method described in the first aspect.

[0022] During the preparation process, the gel body is divided into two parts, a first gel and a second gel, and prepared in two separate steps. This not only achieves a multi-level hierarchical pore structure within the gel, but also allows for the embedded composite of two gels of different densities. This structure has the advantages of allowing the ionic solution to diffuse and be incorporated more evenly into the gel structure, while effectively preventing water loss from the gel, thereby maintaining stability and flexibility for a longer period of time. The present invention has demonstrated that the gel material exhibits excellent mechanical properties, outstanding tensile strength and flexibility, and good electrical conductivity, making it highly suitable for use in wearable electronic devices. In particular, the tensile strain properties of the gel in triboelectric nanogenerators (TGNs) ensure stable output even in complex bending and folding configurations.

[0023] Therefore, the third aspect of the present invention provides the use of the multi-level porous conductive gel described in the second aspect in the preparation of a friction nanogenerator.

[0024] In a fourth aspect, a triboelectric nanogenerator is provided, comprising a positive electrode friction pair and a negative electrode friction pair arranged opposite to each other and fixed by a pair of elastic bodies; Among them, the positive electrode friction pair includes a first substrate, a first gel, a positive friction layer and a first wire. The main part of the flexible substrate protrudes to one side in the shape of a "J". The multi-level porous conductive gel described in the second aspect is fixed in the cavity and covers the positive friction layer to realize the encapsulation of the multi-level porous conductive gel. One end of the first wire is fixed in the gap between the multi-level porous conductive gel and the flexible substrate, and the other end extends to the outside of the flexible substrate; the negative electrode friction pair includes a second substrate, a second gel, a negative friction layer and a second wire, which is set up in the same way as the positive electrode friction pair. The difference is that the negative friction layer and the positive friction layer are materials with different triboelectric properties, and the extension direction of the second wire is opposite to that of the first wire.

[0025] The above-mentioned triboelectric nanogenerator also has the following preferred technical solutions: The first substrate and the second substrate are made of flexible materials so as to better fit the gel and adapt to various complex deformations of the wearable device. A feasible material is Ecoflex.

[0026] The first conductive wire and the second conductive wire are metal wires, and those skilled in the art can make conventional selections based on factors such as cost, such as copper wire, iron wire, etc.

[0027] The elastomer may be made of materials such as silicone rubber, rubber, polyurethane, polyester, and styrene elastomer materials. The purpose is to enable the positive friction layer and the negative friction layer to contact under the action of external force, and to maintain a certain distance between the two in a static state.

[0028] The positive friction layer and the negative friction layer may be made of materials such as nylon, polyimide, polylactic acid, collagen, silk, zinc oxide nanowires, polydimethylsiloxane, fluorinated PDMS, polyvinylidene fluoride, polytetrafluoroethylene, PVDF / MXene nanofibers, and carbon nanotube-doped elastomers. In one embodiment verified by the present invention, the positive friction layer is made of polydimethylsiloxane, and the negative friction layer is made of polytetrafluoroethylene.

[0029] Compared with the prior art, the present invention has the following beneficial effects: 1. The reaction precursors used in the present invention are all food-grade high-safety materials, ensuring the non-toxicity and degradability of the prepared gel, meeting the requirements of environmental friendliness and biosafety.

[0030] 2. Through freeze-drying and the interactive embedding of gels of different densities, a multi-level hierarchical pore structure is prepared, which can better prevent the loss of water or ion solution, achieve long-term stability and good flexibility.

[0031] 3. The flexible friction nanogenerator constructed based on this gel not only exhibits excellent electrical output performance, but can also be used in a variety of different scenarios, such as wearable clothing and direct contact with human skin, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0033] Figure 1 This is a graph showing the tensile strength of the multi-level porous conductive gel described in Example 1; Figure 2 Schematic diagram of the structure of the triboelectric nanogenerator described in Example 2; Figure 3 2 is a front view of the triboelectric nanogenerator described in Example 2; above Figure 2-Figure 3 In the figure, 101 is the first substrate, 102 is the first gel, 103 is the positive friction layer, 104 is the first conductor, 105 is the first elastomer, 201 is the first substrate, 202 is the first gel, 203 is the negative friction layer, 204 is the second conductor, and 205 is the second elastomer. DETAILED DESCRIPTION

[0034] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0036] In the context of this specification, the word "comprising" is understood to mean "including especially". It should not be interpreted as "consisting only of".

[0037] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0038] Example 1 In this embodiment, a multi-level porous conductive gel is provided, and its preparation method is as follows: (1) Add 2 g of hydroxypropyl methylcellulose, 2 g of chitosan, 2 g of gelatin, 1.0 g of potassium sorbate, 0.5 g of citric acid, 0.9 g of sodium gluconate, and 0.5 mL of glycerol to 100 mL of deionized water and stir at room temperature for 1 h. Stir the mixture in a 40 °C water bath for another 1 h, then add 0.3 g of ammonium carbonate (pore former) and stir rapidly for 0.1 h to form a uniformly dispersed mixture. The mixed solution was transferred to a microwave reaction device and heated to 75°C with a microwave power of 300W and kept warm for 0.2h to induce thermal decomposition of the pore-forming agent. The mixture was then rapidly cooled to room temperature to obtain a primary gel. The primary gel was washed multiple times with deionized water until no residual pore-forming agent components were detected in the washing liquid. After washing, the mixture was naturally dried at room temperature and then freeze-dried, including: freezing (-30°C, 5h), heating (-15°C, 3h), sublimation (-5°C, vacuum degree of 6Pa, 18h) and post-drying (25°C, 2h) to obtain a first gel with a three-dimensional hierarchical pore structure. The first gel also served as the template and matrix of the final product.

[0039] (2) Add 2 g of hydroxypropyl methylcellulose, 2 g of chitosan, 2 g of gelatin, 1.0 g of potassium sorbate, 0.5 g of citric acid, 0.9 g of sodium gluconate and 0.5 mL of glycerol to 50 mL of deionized water and stir in a 40 °C water bath for 1 h. After raising the water bath temperature to 75 °C, add 0.1 g of xanthan gum and 0.1 g of coconut oil and continue stirring for 1 h to obtain a second gel with a lower water content.

[0040] (3) In a closed space, slowly add the second gel at a temperature of 80°C to the first gel while maintaining a vacuum degree of 16 kPa, so that the second gel gradually penetrates into the three-dimensional pore structure of the first gel; continue this operation until the penetration process is complete, and obtain a composite gel containing the first gel and the second gel. The composite gel is dried according to a freeze-drying process of freezing (-30°C, 5), heating (-15°C, 3h), sublimation (-5°C, vacuum degree of 6Pa, 18h) and post-drying (25°C, 2h) to obtain a structurally stable gel complex.

[0041] (4) The gel complex was immersed in a 0.08 mol / L sodium chloride ion solution and treated at room temperature under a vacuum of 12 kPa for 20 min while being magnetically stirred at 150 rpm to allow the ions to diffuse uniformly and be doped into the gel structure. The conductivity of the gel complex was as high as 15.2 S / m, and the tensile performance test showed that the gel had excellent mechanical properties ( Figure 1 ), its tensile strength reaches 10.12MPa and its elongation at break reaches 1067.2%, showing high strength and flexibility.

[0042] Example 2 In this embodiment, a friction nanogenerator for a wearable device is provided. The structure of the friction nanogenerator is as follows: Figure 2 or Figure 3 As shown, it includes a positive friction pair and a negative friction pair, which are fixed by a first elastic body 105 and a second elastic body 205.

[0043] The positive friction pair includes a first substrate 101, a first gel 102, a positive friction layer 103, and a first conductor 104. The first substrate 101 is an Ecoflex substrate, with the main body protruding to one side in a "J" shape. The cavity holds the first gel 102. The first conductor 104 is a copper wire, with one end positioned between the first gel 102 and the first substrate 101 and the other end extending outward along the edge of the first substrate 101. The positive friction layer 103 is made of polydimethylsiloxane.

[0044] The assembly method of the above-mentioned positive electrode friction pair is as follows: An Ecoflex substrate was processed into a "J"-shaped structure to serve as first substrate 101. One end of a first conductor 104 was placed on the protrusion of first substrate 101. The gel prepared in Example 1 was rapidly heated to a viscous state, and the bottom of the gel was then laminated to the copper conductor and Ecoflex, ensuring close contact. This formed first gel 102. Subsequently, the top of the gel was rapidly heated to a viscous state and then laminated to polytetrafluoroethylene, forming positive friction layer 103. Polyvinyl chloride tape secured positive friction layer 103 to first substrate 101.

[0045] The above-mentioned negative electrode friction pair includes a second substrate 201, a second gel 202, a negative friction layer 203, and a second wire 204. Its structure and preparation steps are the same as those of the positive electrode friction pair. The difference is that the material of the negative friction layer 203 is polytetrafluoroethylene.

[0046] The first and second elastomers 105 and 205 are made of silicone rubber, and the triboelectric nanogenerator is an elastically deformable integrated structure. When an external force presses on the polydimethylsiloxane surface of the positive friction pair, the device's contact and separation process is achieved, generating electrical energy output.

[0047] According to the national standard GB / T 45525.2-2025 "Nanotechnology Nanogenerators Part 2: Test Methods for Electrical Performance of Triboelectric Nanogenerators", the open circuit voltage of the triboelectric nanogenerator was measured to be 40.7V, the short-circuit current Isc was 0.3μA, and the short-circuit transfer charge was 10.3nC, showing excellent electrical output performance and the potential for application in flexible wearable electronic devices.

[0048] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a multi-level porous conductive gel, characterized in that: The steps include: (1) The base polymer, antibacterial agent, pH regulator, chelating agent and moisturizing agent were mixed in a mass ratio of 1: 0.07-0.38: 0.04-0.19: 0.11-0.25: 0.07-0.18: 13.57-26.25, and water was added and stirred at room temperature for 0.5-3 h. The mixture was further stirred in a water bath at 35-50 °C for 0.2-3 h. The pore-forming agent was then added and stirred quickly. The mixture was heated to 70-80 °C and kept warm for 0.1-0.5 h to obtain a primary gel, which was then freeze-dried to obtain the first gel. (2) Add water to the base polymer, antibacterial agent, pH regulator, chelating agent and moisturizing agent and stir in a water bath at 40-60°C for 0.2-3h. After raising the temperature to 70-85°C, add the thickener and defoaming agent and continue stirring for 0.2-2h to obtain a second gel; the mass ratio of the base polymer, antibacterial agent, pH regulator, chelating agent, moisturizing agent, thickener and defoaming agent is 1: 0.07-0.38: 0.04-0.19: 0.11-0.25: 0.07-0.18: 6.43-13.75: 0.01-0.13: 0.007-0.05; (3) In a closed space, slowly add the second gel at a temperature of 70-85°C to the first gel, maintain the ambient vacuum at 15-20 kPa to allow the second gel to completely penetrate the first gel to obtain a composite gel, and freeze-dry to obtain a gel complex; (4) Immerse the gel complex in a 0.05-1 mol / L salt or ion solution, treat it at a vacuum of 10-15 kPa and room temperature for 10-30 min, and stir it magnetically at 100-200 rpm to obtain a multi-level porous conductive gel.

2. The method for preparing the multi-level porous conductive gel according to claim 1, wherein: In step (1), the matrix polymer is one or more of hydroxypropyl methylcellulose, chitosan, sodium hyaluronate, gelatin, xanthan gum, sodium alginate, pectin, casein, and soy protein mixed in any proportion; The antibacterial agent is any one of potassium sorbate, tea tree oil, garlic extract, peppermint oil, rosemary extract, turmeric extract, lauryl alcohol, citric acid, lactic acid, and hydrochloric acid; The pH regulator is any one of citric acid, lactic acid, sodium citrate, sodium acetate, and sodium bicarbonate; The complexing agent is any one of citric acid, sodium gluconate, tannic acid, and gluconic acid; The moisturizing agent is any one of glycerin, hyaluronic acid, panthenol, trehalose, squalene, and shea butter; The pore-forming agent is any one of ammonium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, zinc carbonate, ammonium nitrate, and ammonium nitrite; The mass ratio of the pore-forming agent to the matrix polymer is 1:8-35; After adding the pore-forming agent, preferably microwave heating is used to promote thermal decomposition of the pore-forming agent, wherein the power of the microwave is 100-600W; The primary gel is washed multiple times with deionized water until no residual pore-forming agent components are detected in the washing solution; after washing, it is naturally dried at room temperature and then freeze-dried. The freeze-drying procedure is as follows: freezing at -40~-20°C for 5.5~6.5 hours, heating to -20~-10°C and maintaining for 2~4 hours, heating to -10~0°C, maintaining a vacuum degree of 5~10 Pa for 12~24 hours for sublimation, and drying at 25~30°C for 2~4 hours.

3. The method for preparing the multi-level porous conductive gel according to claim 1, wherein: In step (2), the thickener is any one of carbomer, xanthan gum, gelatin, modified starch, methyl cellulose, low methoxyl pectin, gum arabic, and pectin; The defoaming agent is any one of olive oil, rapeseed oil, coconut oil, dimethyl silicone oil, saponin, lecithin, calcium chloride, and sodium bicarbonate.

4. The method for preparing the multi-level porous conductive gel according to claim 1, wherein: In step (3), the freeze-drying procedure is as follows: freezing at -40~-20°C for 5.5~6.5h, heating to -20~-10°C and maintaining for 2~4h, heating to -10~0°C, maintaining a vacuum degree of 5~10Pa for 12~24h for sublimation, and drying at 25~30°C for 2~4h.

5. The method for preparing the multi-level porous conductive gel according to claim 1, wherein: In step (4), the salt or ion solution is any one of an aqueous solution of sodium citrate, sodium lactate, sodium malate, sodium chloride, potassium chloride, magnesium chloride, and sodium bicarbonate.

6. A multi-level porous conductive gel prepared by the method according to any one of claims 1 to 5.

7. Use of the multi-level porous conductive gel according to claim 6 in the preparation of a triboelectric nanogenerator.

8. A triboelectric nanogenerator, characterized in that: It includes a positive friction pair and a negative friction pair arranged opposite to each other, which are fixed by a pair of elastomers; wherein, the positive friction pair includes a first substrate, a first gel, a positive friction layer and a first wire, the main part of the flexible substrate protrudes to one side in a "J" shape, the multi-level porous conductive gel is fixed in the cavity and covers the positive friction layer to achieve the encapsulation of the multi-level porous conductive gel, one end of the first wire is fixed in the gap between the multi-level porous conductive gel and the flexible substrate, and the other end extends to the outside of the flexible substrate; the negative friction pair includes a second substrate, a second gel, a negative friction layer and a second wire, and is arranged in the same way as the positive friction pair, the difference being that the negative friction layer and the positive friction layer are made of materials with different triboelectric properties, and the extension direction of the second wire is opposite to that of the first wire.

9. The triboelectric nanogenerator according to claim 8, wherein: The first substrate and the second substrate are made of flexible materials; The first conductive wire and the second conductive wire are metal wires; The elastomer is selected from silicone rubber, rubber, polyurethane, polyester or styrene elastomer materials; The positive friction layer and the negative friction layer are selected from nylon, polyimide, polylactic acid, collagen, silk, zinc oxide nanowire, polydimethylsiloxane, fluorinated PDMS, polyvinylidene fluoride, polytetrafluoroethylene, PVDF / MXene nanofiber or carbon nanotube-doped elastomer.

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