Super-strong, super-tough and all-weather fatigue fracture resistant conductive hydrogel and preparation method and use thereof

Abstract

The application provides a super-strong, super-tough and all-weather anti-fatigue fracture conductive hydrogel which is prepared by using an ice template method and taking a conductive filler, a polymer and water as raw materials, wherein the polymer accounts for 1wt%-40wt% of the total amount of the raw materials; and the conductive filler accounts for 0.01mg / mL-10mg / mL of the total amount of the raw materials. The application also provides a preparation method and application of the hydrogel. The application realizes all-weather anti-fatigue fracture of the hydrogel material for the first time, and the prepared hydrogel has excellent mechanical properties in the orientation direction and can maintain the mechanical properties and conductivity in a wide temperature range. The realization of the super-high fatigue threshold and the diversified scene application provide an opportunity for the consideration of the related factors such as the industrialized production, low cost and durability of the flexible electronic field and the bionic material, and have a good development prospect. In addition, the preparation method of the application has universality for the toughening hydrogel of different polymers.

Description

Technical Field

[0001] This invention belongs to the field of flexible polymer materials, specifically relating to an ultra-strong, ultra-tough, all-weather fatigue-resistant conductive hydrogel, its preparation method, and its application. Background Technology

[0002] Hydrogels, as hydrophilic materials with water as their main component, are highly effective in simulating biological tissues and have therefore attracted widespread attention in the field of tissue engineering. Conductive hydrogels, by enabling electrical conduction, endow the material with additional functions, and these hydrogels have great application potential in wearable and implantable medical sensors, neural network simulation, soft robotics, and electrically stimulated drug delivery.

[0003] However, these applications typically require hydrogels to possess excellent mechanical properties and conductivity. Currently, hydrogels with these characteristics have been widely reported. For example, application number 202211009303.0, entitled "A Graphene-Based Conductive Hydrogel and Its Preparation Method and Application," discloses a graphene-based conductive hydrogel and its preparation method and application, belonging to the field of biomaterials technology. The preparation method includes the following steps: mixing graphene with a polyvinyl alcohol solution to obtain a graphene-based polyvinyl alcohol mixture; adding chitosan to the graphene-based polyvinyl alcohol mixture and mixing it evenly, then allowing it to stand for hydration to obtain a graphene-based polyvinyl alcohol-chitosan mixture; and immersing the graphene-based polyvinyl alcohol-chitosan mixture in a sodium citrate solution after freeze-thaw cycles to obtain a graphene-based conductive hydrogel. The graphene-based conductive hydrogel provided by this invention possesses excellent mechanical properties, conductivity, and flexibility; therefore, the graphene-based conductive hydrogel provided by this invention has broad application prospects in the field of flexible wearable sensors, as well as human-machine interfaces, electronic skin, and other fields. This patent uses a polyvinyl alcohol / chitosan dual-network hydrogel formed by a cyclic freeze-thaw method, which only increases the fracture energy generated by mechanical dissipation of the hydrogel, resulting in significantly poorer mechanical properties. Furthermore, the hydrogel prepared by this patent lacks fatigue fracture resistance and will face a series of problems such as performance distortion during long-term use. Application number 202310899061.5, invention title: A conductive hydrogel with anisotropic mechanoelectric properties, its preparation method and application, provides a conductive hydrogel with anisotropic mechanoelectric properties, its preparation method and application, relating to the field of conductive polymer materials technology. This invention uses a polymer and a paramagnetic electromagnetic nanocomposite as a mixed precursor liquid. The conductive hydrogel prepared by an ice template-assisted magnetic field induction method exhibits significant anisotropic mechanoelectric properties. Both the polymer chains and the electromagnetic nanocomposite are oriented, and the conductive hydrogel shows significant anisotropy in conductivity and sensitivity in orthogonal directions. When applied to wearable electronic devices, it can monitor signals in various complex scenarios. The material described in this patent lacks extreme environment tolerance and fatigue fracture resistance, posing certain problems for long-term application. Furthermore, the process of constructing a highly oriented structure using an ice template with the assistance of a magnetic field is more complex and lacks universality for non-magnetic conductive materials, limiting its application scope. Application number 202011053260.7, invention title: A Low-Temperature Resistant Biomimetic Conductive Hydrogel and its Preparation Method and Application, discloses a low-temperature resistant biomimetic conductive hydrogel and its preparation method and application, belonging to the field of materials preparation technology.First, agarose, monomers, photoinitiator, and crosslinking agent are added to water and stirred until homogeneous. After purging with nitrogen, the solution is heated to 90°C in a constant-temperature oil bath until the agarose dissolves, resulting in a homogeneous solution. The solution is then allowed to cool naturally at room temperature to form a gel, followed by irradiation with ultraviolet light. After drying at room temperature, the gel is immersed in a solution containing inorganic salts and an antifreeze agent, such as alginic acid, mannitol, betaine, glycine, or proline, to obtain a low-temperature resistant biomimetic conductive hydrogel. This invention is simple to operate, easy to prepare, and the preparation process is green, safe, and time-efficient, providing a pathway for preparing multifunctional, high-strength hydrogels. The obtained conductive hydrogel possesses excellent mechanical properties and conductivity, and can be widely applied in fields such as artificial skin, flexible sensors, tissue engineering, and supercapacitors.

[0004] With the rapid development of various fields, higher requirements are being placed on hydrogel materials: namely, the ability to resist fatigue fracture, that is, the ability to resist crack propagation under long-term cyclic loading. Although there are many reports of strong and tough hydrogels that can resist notch propagation under a single cycle of loading, the fatigue threshold (the minimum fracture energy required for crack propagation under cyclic loading) of these gels is generally below 100 J / m2, and fatigue fracture will still occur under long-term cyclic loading.

[0005] Furthermore, hydrogel materials inevitably face the following problems in practical applications: 1) When the operating temperature is below 0℃ (e.g., in high-latitude regions, mountains, cold storage, etc.), the water molecules in the hydrogel freeze, causing the hydrogel to lose its elasticity and fracture brittlely, leading to material and device failure; 2) During long-term use, especially when the operating temperature is high (e.g., in equatorial regions) or the ambient humidity is low (e.g., in desert regions), the water molecules in the hydrogel will continuously evaporate into the air, causing the hydrogel to dehydrate, resulting in unstable performance or even failure of hydrogel-based electronic devices. Although encapsulation with elastomers can effectively mitigate water molecule loss, it is still difficult to meet the requirements for long-term use in high-temperature and low-humidity environments.

[0006] The two issues mentioned above severely limit the long-term practical application of conductive hydrogels. Therefore, how to endow hydrogel materials with fatigue fracture resistance and freeze-thaw resistance through reasonable structural design, so as to meet the long-term reliability and tolerance of hydrogel-based devices under extreme environments (low temperature and high temperature), is currently a cutting-edge research direction in the field of hydrogels. Summary of the Invention

[0007] The purpose of this invention is to provide an ultra-strong, ultra-tough, and all-weather fatigue-resistant conductive hydrogel material, its preparation method, and its application.

[0008] This invention provides an ultra-strong, ultra-tough, and all-weather fatigue-fracture-resistant conductive hydrogel, which is prepared by an ice-templating method using conductive fillers, polymers, and water as raw materials. The polymer content ranges from 1 wt% to 40% of the total raw materials.

[0009] wt%; the amount of conductive filler used is 0.01 mg / mL to 10 mg / mL;

[0010] The polymer is selected from any one or a mixture of two or more of the following: chitosan, alginate, sodium alginate, guar gum, gelatin, xanthan gum, cellulose, sodium carboxymethyl cellulose, hydroxyethyl cellulose, polypyrrole, polyaniline, polyethylene glycol, polyvinyl alcohol, polyoxyethylene, polyacrylamide, polyacrylic acid, sodium polyacrylate, polymethacrylic acid, polyhydroxyethyl methacrylate, poly(ethylene glycol) methyl ether acrylate, polyacrylamide-acrylic acid copolymer, poly(3,4-ethylenedioxythiophene), and polystyrene sulfonate.

[0011] The conductive filler is selected from graphene, silver nanowires, copper nanowires, gold nanowires, and Ti3CNT. x Ti3C2T x V2T x Ti2CT x Any one or a mixture of two or more of the following: carbon nanotubes, copper oxide, aluminum oxide, zinc oxide, iron tetroxide, and ruthenium dioxide.

[0012] More preferably, the polymer accounts for 5 wt% to 25 wt% of the total raw materials; the conductive filler accounts for 0.1 mg / mL to 10 mg / mL.

[0013] More preferably, the polymer accounts for 5 wt% to 20 wt% of the total raw materials; the conductive filler accounts for 0.5 mg / mL to 5 mg / mL.

[0014] The raw materials also include an antifreeze agent, which is selected from any one or a mixture of two or more of methanol, ethanol, ethylene glycol, propylene glycol, glycerin, and sorbitol.

[0015] The raw materials mentioned are:

[0016] Cellulose accounts for 10 wt% of the total raw materials, graphene 2.0 mg / mL, and ethanol is used as the antifreeze agent; or

[0017] The amount of polyethylene glycol used accounts for 12.5 wt% of the total raw materials, carbon nanotubes 2.0 mg / mL, and the antifreeze agent is ethylene glycol; or

[0018] Polyvinyl alcohol accounts for 12.5 wt% of the total raw materials, carbon nanotubes are 1.0 mg / mL, and ethylene glycol is the antifreeze agent; or

[0019] Gelatin accounts for 10 wt% of the total raw materials, and Ti3C2T x 1.0 mg / mL, with glycerol as the antifreeze; or

[0020] Polyacrylamide accounted for 12.5 wt% of the total raw materials, and V2T x 2.0 mg / mL, with sorbitol as the antifreeze; or

[0021] Hydroxyethyl cellulose accounts for 15 wt% of the total raw materials, silver nanowires are 3.0 mg / mL, and glycerol is used as the antifreeze agent; or

[0022] Hydroxyethyl cellulose accounts for 15 wt% of the total raw materials, silver nanowires are 3.0 mg / mL, and glycerol is used as the antifreeze agent.

[0023] This invention also provides a method for preparing the aforementioned ultra-strong, ultra-tough, and all-weather fatigue-fracture resistant conductive hydrogel, which includes the following steps:

[0024] a. Raw materials: conductive filler, polymer, water, antifreeze;

[0025] b. Mix the conductive filler with the polymer solution and construct the oriented structure using the ice template method combined with freeze drying; c. After freeze drying, vacuum anneal and soak in an antifreeze agent to replace the solvent, thus obtaining the final product.

[0026] In step b, the freeze-drying is carried out in liquid nitrogen at a temperature of -196°C, under a temperature gradient formed by the transition from liquid nitrogen temperature to room temperature, and then freeze-dried at -80°C for more than 36 hours.

[0027] Step c: Vacuum annealing for 0–150 min; immersion time in antifreeze for 0–24 h;

[0028] In step c, vacuum annealing is performed for 30–120 min; preferably, vacuum annealing is performed for 60–120 min.

[0029] The soaking time of the antifreeze is 0 to 12 hours; preferably, the soaking time of the antifreeze is 0.25 to 4.0 hours.

[0030] In step c, after vacuum annealing, the gel is soaked in water for at least 24 hours.

[0031] This invention also provides applications of conductive hydrogels in the fields of artificial skin, soft robots, artificial ligaments, and flexible electronic devices.

[0032] This invention provides a method for preparing an ultra-strong, ultra-tough, and all-weather fatigue-resistant conductive hydrogel material. By combining the ice-templating method and annealing process with a solvent displacement strategy, a fatigue-resistant conductive hydrogel with extreme environmental tolerance was successfully prepared. The material surpasses the data reported in current literature in multiple aspects, including fatigue threshold, mechanical properties, and application scenarios.

[0033] In summary, this invention achieves all-weather fatigue fracture resistance in hydrogel materials for the first time. The prepared hydrogels exhibit excellent mechanical properties in the orientation direction and maintain their mechanical properties and conductivity over a wide temperature range. The realization of ultra-high fatigue thresholds and their application in diverse scenarios provides an opportunity for the industrial production of flexible electronics and biomimetic materials, considering factors such as low cost and durability, and has promising development prospects. Furthermore, the preparation method of this invention, based on the toughening of hydrogels using different polymers, has universal applicability.

[0034] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0035] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Attached Figure Description

[0036] Figure 1 This is a tensile curve of the ultra-strong, ultra-tough, and all-weather fatigue-resistant conductive hydrogel material prepared in Example 12 after 10,000 cycles at 200% strain at room temperature. Detailed Implementation

[0037] Example 1

[0038] First, a chitosan solution (prepared with deionized water to form a 20 wt% chitosan solution and then diluted) was diluted to 10 wt% and mixed with graphene to prepare a chitosan / graphene solution with a graphene concentration of 2.0 mg / mL.

[0039] The prepared solution was then injected into a mold made of polytetrafluoroethylene sheet and copper plate. An oriented structure was constructed using the ice template method. After freezing under a temperature gradient (liquid nitrogen temperature of -196℃, formed by the transition from liquid nitrogen temperature to room temperature) created by liquid nitrogen as a cold source, the solution was freeze-dried at -80℃ for more than 36 hours to obtain chitosan / graphene aerogel.

[0040] The obtained aerogel was annealed in vacuum at 100°C for 90 min and then soaked in water for more than 24 h until it reached equilibrium.

[0041] Finally, the prepared hydrogel was immersed in anhydrous ethanol (an antifreeze) for solvent replacement for 0.25 h to obtain the conductive hydrogel of the present invention. The performance test results are shown in Table 1.

[0042] The parameters and performance test results of Examples 2-34 are shown in Table 1.

[0043] The annealing times in Examples 35-40 were different, while other conditions were the same as in Example 34, wherein:

[0044] Example 35

[0045] The annealing time was controlled at 30 minutes.

[0046] Example 36

[0047] The annealing time was controlled at 60 minutes.

[0048] Example 37

[0049] The annealing time was controlled at 120 minutes.

[0050] Example 38

[0051] The annealing time was controlled at 150 min.

[0052] Example 39

[0053] The annealing time was controlled at 180 min.

[0054] Example 40

[0055] The annealing time was controlled at 210 min.

[0056] Comparative Example 1

[0057] The amount of conductive filler added was 0 mg / mL, the antifreeze soaking time was 0 min, and other conditions were the same as in Example 1. The performance test results are shown in Table 1.

[0058] Comparative Example 2

[0059] The antifreeze soaking time was 0 min, and other conditions were the same as in Example 1. The performance test results are shown in Table 1.

[0060] Comparative Example 3

[0061] The amount of conductive filler added was 0 mg / mL, and other conditions were the same as in Example 1. The performance test results are shown in Table 1.

[0062] Comparative Example 4

[0063] The amount of conductive filler added was 0 mg / mL, the antifreeze soaking time was 0 min, and other conditions were the same as in Example 17. The performance test results are shown in Table 1.

[0064] Comparative Example 5

[0065] The antifreeze soaking time was 0 min, and other conditions were the same as in Example 17. The performance test results are shown in Table 1.

[0066] Comparative Example 6

[0067] The amount of conductive filler added was 0 mg / mL, and other conditions were the same as in Example 17. The performance test results are shown in Table 1.

[0068] Comparative Example 7

[0069] The amount of conductive filler added was 0 mg / mL, the antifreeze soaking time was 0 min, and other conditions were the same as in Example 22. The performance test results are shown in Table 1.

[0070] Comparative Example 8

[0071] The antifreeze soaking time was 0 min, and other conditions were the same as in Example 22. The performance test results are shown in Table 1.

[0072] Comparative Example 9

[0073] The amount of conductive filler added was 0 mg / mL, the antifreeze soaking time was 0 min, and other conditions were the same as in Example 13. The performance test results are shown in Table 1.

[0074] Comparative Example 10

[0075] The antifreeze soaking time was 0 min, and other conditions were the same as in Example 13. The performance test results are shown in Table 1.

[0076] Hydrogels were prepared according to the above method, and then their performance was tested. The experimental results are shown in Table 1.

[0077] The mechanical performance evaluation criteria are as follows:

[0078]

[0079] In mechanical performance evaluation, the more "+" signs there are, the better the mechanical performance.

[0080] The electrical conductivity and antifreeze properties are evaluated as follows:

[0081] It does not have electrical conductivity or antifreeze properties: ×

[0082] Possesses conductive or antifreeze properties: √

[0083] In the table, "--" indicates that no relevant raw materials were added or no relevant experiments were conducted.

[0084] Table 1 Performance Test Results

[0085]

[0086]

[0087] The above results demonstrate that the hydrogels prepared using the method proposed in this invention possess excellent mechanical properties, unaffected by the type of polymer material or conductive filler. Furthermore, different types of antifreeze agents exhibit significant differences in stress and strain, with those soaked in antifreeze agents for 0.25–4 hours showing the best mechanical properties. In addition, applying the preparation method proposed in this invention to the preparation of hydrogels based on different polymer precursor materials also results in a significant improvement in mechanical properties compared to traditional methods.

[0088] in, Figure 1 This is a tensile curve of the notched, ultra-strong, ultra-tough, and all-weather fatigue-resistant conductive hydrogel material prepared in Example 12, after 10,000 cycles of tensile testing at 200% strain at room temperature. The horizontal and vertical axes represent stress and strain, respectively, indicating that the notch in the hydrogel material does not propagate after 10,000 cycles of tensile testing. The fracture of the "sacrificial bonds" (mainly reversible hydrogen bonds) constructed within the system provides strong energy dissipation, resulting in high mechanical strength, stable above 4 MPa, and excellent fatigue fracture resistance.

[0089] In summary, this invention provides a novel method for preparing fatigue-resistant, fracture-resistant conductive hydrogels. This not only broadens the application fields of toughened hydrogels but also offers new technical approaches and methods for preparing multifunctional toughened hydrogels based on other polymer materials. Furthermore, the sample preparation process is relatively simple, allows for a wide selection of materials, and yields hydrogel materials with high strength. This provides an opportunity for the industrial production of flexible electronics and biomimetic materials, considering factors such as low cost and durability, and demonstrates promising development prospects.

Claims

1. A super-strong, super-tough, and all-weather fatigue-fracture-resistant conductive hydrogel, characterized in that: Take the raw materials: conductive filler, polymer, water, and antifreeze. Mix the conductive filler with the polymer solution, and construct the oriented structure using the ice template method combined with freeze drying. After freeze drying, vacuum anneal and solvent replacement is performed by soaking in antifreeze. The soaking time of the antifreeze is 0.5~4.0 h. The polymer is cellulose, accounting for 10 wt% of the total raw materials; the conductive filler is graphene at 2.0 mg / mL; and the antifreeze agent is ethanol; or, The polymer is polyethylene glycol, accounting for 12.5 wt% of the total raw materials; the conductive filler is carbon nanotubes at 2.0 mg / mL; and the antifreeze agent is ethylene glycol; or, The polymer is polyvinyl alcohol, accounting for 12.5 wt% of the total raw materials; the conductive filler is carbon nanotubes at 1.0 mg / mL; and the antifreeze agent is ethylene glycol; or, The polymer is gelatin, accounting for 10 wt% of the total raw materials, and the conductive filler is Ti3C2T. x 1.0 mg / mL, with glycerol as the antifreeze; or, The polymer is hydroxyethyl cellulose, accounting for 15 wt% of the total raw materials; the conductive filler is silver nanowires at 3.0 mg / mL; and the antifreeze agent is glycerol.

2. A method for preparing the ultra-strong, ultra-tough, and all-weather fatigue fracture resistant conductive hydrogel according to claim 1, characterized in that: It includes the following steps: a. Raw materials: conductive filler, polymer, water, antifreeze; b. Mix the conductive filler with the polymer solution and construct the oriented structure using the ice template method combined with freeze drying; c. After freeze-drying, vacuum annealing and solvent replacement by soaking in an antifreeze agent are performed to obtain the final product.

3. The method for preparing the ultra-strong, ultra-tough, and all-weather fatigue fracture resistant conductive hydrogel according to claim 2, characterized in that: The freeze-drying described in step b involves freezing in liquid nitrogen at a temperature of -196°C, under a temperature gradient formed by the transition from liquid nitrogen temperature to room temperature, followed by freeze-drying at -80°C for more than 36 hours. Step c describes vacuum annealing for 0~150 min.

4. The method for preparing the ultra-strong, ultra-tough, and all-weather fatigue fracture resistant conductive hydrogel according to claim 3, characterized in that: Step c: Vacuum annealing for 30~120 min.

5. The method for preparing the ultra-strong, ultra-tough, and all-weather fatigue fracture resistant conductive hydrogel according to claim 4, characterized in that: Step c: Vacuum annealing for 60~120 min.

6. The method for preparing the ultra-strong, ultra-tough, and all-weather fatigue fracture resistant conductive hydrogel according to any one of claims 2-5, characterized in that: After vacuum annealing as described in step c, the gel is soaked in water for at least 24 hours.

7. The application of the conductive hydrogel according to claim 1 in the preparation of artificial skin, soft robots, artificial ligaments and flexible electronic devices.

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