A myofibrillar protein-based double-network conductive hydrogel, and a preparation method and application thereof

Abstract

The application provides a kind of double network conductive hydrogel based on myofibrillar protein and its preparation method and application, it is related to biomaterial field.The preparation method includes the following steps: myofibrillar protein solution and oxidized dextran solution are mixed uniformly, obtain mixed solution 1;Mixed solution 1 is mixed uniformly with sodium alginate solution and 1-butyl-3-methyl imidazole chloride salt, obtain mixed solution 2;Mixed solution 2 is heated, and cooling is formed, is soaked in calcium chloride solution and carries out ion crosslinking, obtains double network conductive hydrogel.The application innovatively uses natural myofibrillar protein as gel raw material, deeply excavates the structure potential of myofibrillar protein, uses double network synergistic enhancement strategy to overcome the defect of pure natural protein gel brittle, and combined with green ionic liquid as conductive filler, the prepared hydrogel has excellent mechanical properties, stable ionic conductivity, good biocompatibility and degradability.

Description

Technical Field

[0001] This invention relates to the field of biomaterials, specifically to a dual-network conductive hydrogel based on myofibrillar protein, its preparation method, and its applications. Background Technology

[0002] With the booming development of the Internet of Things and smart wearable devices, flexible sensing materials that combine comfort, multifunctionality, and biocompatibility have become a hot research topic. Hydrogels, due to their high water content, soft texture, and tunable properties, are considered ideal matrices for biomimetic skin and the construction of flexible sensors. However, currently widely used synthetic polymer hydrogels such as polyacrylamide and polyvinyl alcohol often contain monomers (such as acrylamide, a Group 2A carcinogen), crosslinking agents, and initiators that are generally biotoxic. Even if the polymer is non-toxic after polymerization, monomer residues or polymer decomposition may still exist, severely limiting their safe application in health monitoring, implantable medical devices, and other scenarios. Therefore, renewable and environmentally friendly natural polymers are increasingly becoming the most promising alternative to traditional synthetic materials.

[0003] Natural proteins (such as collagen and silk fibroin) are ideal materials for constructing hydrogels due to their inherent biocompatibility and biodegradability. However, these pure natural protein hydrogels often have inherent defects in mechanical properties, such as low strength and poor toughness, making them difficult to repeatedly stretch and deform, which seriously restricts their application as flexible sensing materials.

[0004] Achieving flexible sensing not only requires a biocompatible gel framework, but also presents challenges in endowing hydrogels with stable and reliable electrical sensing functions. Currently used conductive fillers, such as metal nanoparticles and carbon nanotubes, have a large mechanical mismatch between their high modulus and the soft hydrogel matrix, which easily leads to weak interfacial bonding, poor device tensile strength, and signal response hysteresis.

[0005] Therefore, how to construct a novel hydrogel material that combines excellent mechanical properties, stable ionic conductivity, good biocompatibility, and biodegradability is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of existing sensing hydrogels in that they are difficult to simultaneously achieve biocompatibility, mechanical properties and ionic conductivity stability, thereby providing a dual-network conductive hydrogel based on myofibril protein, its preparation method and application.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a dual-network conductive hydrogel based on myofibrillar protein, comprising the following steps: S1. Mix the myofibrillar protein solution and the oxidized dextran solution evenly to obtain mixture 1; S2. Mix the mixture 1 with sodium alginate solution and 1-butyl-3-methylimidazolium chloride to obtain mixture 2. S3. The mixture 2 is heated, cooled and shaped, and then immersed in calcium chloride solution for ionic cross-linking to obtain a double-network conductive hydrogel.

[0009] Further, in step S1, the myofibrillar protein solution is obtained by dissolving myofibrillar protein in PBS buffer.

[0010] Furthermore, the PBS buffer solution has the following composition: 0.6 mol / L NaCl, 20 mmol / L K2HPO4 / KH2PO4, and pH 7.0.

[0011] Further, in step S1, the protein concentration in the myofibrillar protein solution is 20-50 mg / mL, preferably 40 mg / mL.

[0012] Further, in step S1, the concentration of the oxidized dextran solution is 20~25 mg / mL, preferably 20 mg / mL.

[0013] Furthermore, in step S1, the oxidized dextran solution is prepared using the sodium periodate oxidation method.

[0014] Further, in step S1, the degree of oxidation of the oxidized dextran in the oxidized dextran solution is 90.23 ± 0.96%, preferably 90.23%.

[0015] Further, in step S1, the aldehyde content of the oxidized dextran in the oxidized dextran solution is 5.67 ± 0.08 nmol / g, preferably 5.67 nmol / g.

[0016] Further, in step S1, the mass ratio of myofibrillar protein to oxidized dextran in the mixture 1 is 5~20:1, preferably 10:1.

[0017] Further, in step S1, the mixing conditions are: stirring at 800~1500 rpm for 10~15 min, preferably stirring at 1000 rpm for 10 min.

[0018] Further, in step S2, the concentration of the sodium alginate solution is 25~30 mg / mL, preferably 30 mg / mL.

[0019] Further, in step S2, the volume ratio of the sodium alginate solution to the myofibrillar protein solution is 1:5 to 1:2, preferably 1:3.

[0020] Further, in step S2, the mixing conditions are as follows: after mixing the mixture 1 with the sodium alginate solution, stir at 800~1500 rpm for 10~15 min, and then add 1-butyl-3-methylimidazolium chloride and disperse it evenly.

[0021] Further, in step S2, the mixing conditions are as follows: after mixing the mixture 1 with the sodium alginate solution, stir at 1000 rpm for 10 min, and then add 1-butyl-3-methylimidazolium chloride and disperse evenly.

[0022] Further, in step S2, the molar volume ratio of the 1-butyl-3-methylimidazolium chloride to the myofibrillar protein solution is not greater than 1:30 mol / mL, preferably 1:30 mol / mL.

[0023] Furthermore, in step S3, the heating temperature is 50~55 ℃, preferably 55 ℃.

[0024] Furthermore, in step S3, the heating time is 2.5 to 3.5 hours, preferably 3 hours.

[0025] Further, in step S3, the concentration of the calcium chloride solution is 10~30 mg / mL, preferably 20 mg / mL.

[0026] Further, in step S3, the ratio of the sum of the volumes of the mixture 1 and the sodium alginate solution to the volume of the calcium chloride solution is 1 to 3:1, preferably 2:1.

[0027] Furthermore, in step S3, the soaking time is 2 to 4 hours, preferably 3 hours.

[0028] Furthermore, in step S3, the soaking is carried out at room temperature.

[0029] Furthermore, in step S3, before the heating treatment, the mixture 2 is centrifuged at 300-500 rpm for 3-5 min to remove air bubbles.

[0030] Furthermore, in step S3, before the heating treatment, the mixture 2 is centrifuged at 500 rpm for 3 min to remove air bubbles.

[0031] Furthermore, the method for preparing myofibrillar protein in the myofibrillar protein solution includes the following steps: after removing fat and connective tissue from chicken, mince the chicken into a paste; mix the minced chicken with a standard salt solution and homogenize it, then centrifuge to collect the precipitate; mix the precipitate with a KCl solution and homogenize it, then centrifuge to collect the precipitate, thus obtaining the myofibrillar protein.

[0032] Furthermore, the mass ratio of the minced meat to the standard salt solution is 1:3 to 5, preferably 1:4.

[0033] Furthermore, the standard salt solution has the following composition: 0.1 mol / L KCl, 20 mmol / L K2HPO4 / KH2PO4, 2 mmol / L EGTA, 1 mmol / L MgCl2, and pH 7.0.

[0034] Furthermore, the process of adding standard salt solution, mixing and homogenizing, and centrifuging to collect the precipitate is repeated 1 to 3 times.

[0035] Furthermore, the mass ratio of the precipitate to the KCl solution is 1:3~5, preferably 1:4.

[0036] Furthermore, the concentration of the KCl solution is 0.1~0.2 mol / L, preferably 0.1 mol / L.

[0037] Furthermore, the process of adding KCl solution, mixing, homogenizing, and centrifuging to collect the precipitate is repeated 1 to 3 times.

[0038] Furthermore, the homogenization conditions are as follows: homogenize at 0~4 ℃ and 6000~8000 rpm for 1~2 min, with an interval of 20~30 s every working time.

[0039] Furthermore, the homogenization conditions were as follows: homogenization at 4 ℃ and 8000 rpm for 1 min, with a break every 20 s.

[0040] Furthermore, the centrifugation conditions were: 0~4 ℃, 2000~5000 rpm for 10~15 min.

[0041] Furthermore, the centrifugation conditions were: 4 ℃, 2000 rpm for 10 min.

[0042] Furthermore, the preparation method of the oxidized dextran solution includes the following steps: dissolving dextran in deionized water, adding sodium periodate, reacting under light-protected conditions, and after the reaction is complete, adding ethylene glycol to the reaction solution to terminate the reaction, and dialyzing the product obtained after the reaction in deionized water. After the dialysis is completed, the solution in the dialysis bag is collected to obtain the oxidized dextran solution.

[0043] Furthermore, the mass-to-volume ratio of the dextran to the deionized water is 4-5 g:100 mL, preferably 5 g:100 mL.

[0044] Furthermore, the molecular weight of the dextran is 60-70 kDa, preferably 70 kDa.

[0045] Furthermore, the molar ratio of the dextran, the sodium periodate, and the ethylene glycol is 1:1:1.

[0046] Furthermore, the reaction time is 20-30 h, preferably 24 h.

[0047] Furthermore, the reaction proceeds at room temperature.

[0048] Furthermore, the molecular weight cutoff of the dialysis bag is 3000~4000 Da, preferably 3500 Da.

[0049] Furthermore, the dialysis time is 40-50 hours, preferably 48 hours.

[0050] Secondly, the present invention provides a dual-network conductive hydrogel based on myofibrillar protein obtained by the preparation method described above.

[0051] Thirdly, the present invention provides the application of the myofibrillar protein-based dual-network conductive hydrogel obtained by the above preparation method in the preparation of flexible sensors.

[0052] Fourthly, the present invention provides a flexible sensor comprising a dual-network conductive hydrogel based on myofibrillar protein obtained by the aforementioned preparation method.

[0053] Fifthly, the present invention provides a method for fabricating the flexible sensor, comprising the following steps: cutting the myofibril-based dual-network conductive hydrogel into hydrogel sheets; attaching pressure-sensitive adhesive tape or flexible film to the upper and lower surfaces of the hydrogel sheets, and exposing both ends of the hydrogel sheets; clamping the exposed ends of the hydrogel sheets with conductive metal sheets, and connecting wires to the conductive metal sheets at both ends.

[0054] Furthermore, the pressure-sensitive tape is a 3M VHB tape.

[0055] Furthermore, the flexible film is a polydimethylsiloxane film.

[0056] Furthermore, the thickness of the hydrogel sheet is 2-3 mm, preferably 2.5 mm.

[0057] Furthermore, the conductive metal sheet is a soft copper sheet.

[0058] Furthermore, the wires connected to both ends of the hydrogel sheet are connected to a digital source meter to test the real-time resistance change curve over time; the voltage of the digital source meter is set to 4~5 V, preferably 5 V.

[0059] Sixthly, the present invention provides the application of the flexible sensor described above or the flexible sensor obtained by the preparation method described above in the preparation of human motion monitoring sensors, micro-expression monitoring sensors, speech recognition sensors or handwriting recognition sensors.

[0060] The crosslinking mechanism of the dual-network conductive hydrogel provided by this invention is as follows: Figure 1 As shown, the specific principle is as follows: Myofibrillar protein solution and oxidized dextran solution are mixed, then sodium alginate solution is added to the mixture, and an ionic liquid (1-butyl-3-methylimidazolium chloride) is introduced as a conductive filler. After uniform mixing and thermal induction molding, a Schiff base reaction occurs between the amino groups of myofibrillar protein (MP) and the aldehyde groups of oxidized dextran (ODex), forming a first covalent cross-linked network. Myofibrillar protein (MP) and sodium alginate (SA) are connected by hydrogen bonds. Further immersion in calcium chloride solution allows sodium alginate (SA) to react with calcium chloride... 2+ Ionic crosslinking is performed, and the two layers of "eggshell" structure physical network are formed by ionic bonding. Ionic liquids (ILs) are distributed in the network gel structure, thereby constructing a double-network conductive hydrogel.

[0061] Myofibrillar protein is a fibrous protein with the highest structural similarity to human skin. Its molecular chain is rich in various active amino acids and functional groups, exhibiting good biocompatibility and skin affinity. Furthermore, the global poultry industry generates a large amount of waste, and its byproducts are rich in high-quality protein resources such as myofibrillar protein (MP). These byproducts are often processed into low-value feed or fertilizer, or even discarded, leading to environmental problems. This invention, by converting proteins recovered from byproducts into a novel hydrogel material, helps reduce waste and promote environmental sustainability. Currently, there are no reports on the preparation of high-performance sensing hydrogels based on myofibrillar protein.

[0062] The technical solution of this invention has the following advantages: 1. This invention innovatively uses natural myofibrillar protein as a gel raw material, deeply explores the structural potential of myofibrillar protein, and adopts a dual-network synergistic enhancement strategy (based on polysaccharide to construct a dual-network gel structure) to overcome the brittleness of pure natural protein gels. The prepared hydrogel has excellent mechanical properties, such as excellent mechanical strength, toughness, recoverability, elasticity, and fatigue resistance.

[0063] 2. This invention adopts a high-efficiency and high-value-added technical route to transform protein-rich livestock and poultry by-products into functional materials with high added value. This is not only an urgent need for the sustainable development of the food industry, but also of great significance for achieving efficient resource utilization.

[0064] 3. Compared with synthetic hydrogels that use traditional toxic monomers (such as acrylamide) and chemical crosslinking agents, the present invention completely avoids the use of biotoxic substances, all components have good biosafety, and the hydrogel material obtained has good biocompatibility and degradability.

[0065] 4. Compared to composite materials using solid conductive fillers (such as carbon nanotubes and metal nanowires), this invention selects ionic liquids, a green conductive filler, which has good compatibility with polymer networks and high ionic conductivity, laying the foundation for achieving high tensile strength and low hysteresis sensing performance. Simultaneously, 1-butyl-3-methylimidazolium chloride can bind to the natural protein network through multiple molecular interactions (such as hydrogen bonds and ionic bonds), providing both conductivity and a synergistic effect of strengthening and toughening. The use of ionic liquids effectively avoids problems such as weak interfacial bonding and large signal hysteresis caused by modulus mismatch, achieving superior sensing performance.

[0066] 5. The preparation method provided by the present invention is simple and mild, and does not require complex synthesis steps or expensive equipment (such as high-strength homogenization, freeze drying, etc.). It can be formed mainly through physical mixing and controllable gelation process, and has good potential for process scale-up and economy.

[0067] 6. The dual-network conductive hydrogel prepared by this invention has the properties of stretchability, biocompatibility and biodegradability. It can accurately convert mechanical deformation into stable resistance signal changes. This material is suitable for developing high-performance, environmentally friendly skin-like flexible sensing elements and shows broad application prospects in fields such as human motion monitoring and physiological signal capture. It is particularly suitable for biocompatible wearable health monitoring scenarios.

[0068] 7. This invention provides a flexible sensor based on a dual-network conductive hydrogel. By connecting conductive metal sheets and wires to both ends of the hydrogel sheet, sensing signals are acquired. Pressure-sensitive adhesive tape is attached to the surface of the hydrogel sheet to prevent moisture evaporation. When fixed to joints on the body (such as finger joints, wrist joints, elbow joints, and knee joints), it can be used to create a human motion detection sensor; when fixed to the face (such as the chin or forehead), it can be used to create a micro-expression detection sensor; when fixed to the neck and throat, it can be used to create a voice recognition sensor; and a flexible film is attached to the surface of the hydrogel as a writing pad to create a writing recognition sensor. Attached Figure Description

[0069] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0070] Figure 1 This is a diagram illustrating the crosslinking mechanism of the dual-network conductive hydrogel provided by the present invention; Figure 2 This is a comparison diagram of the system state before and after gel formation in Example 1 of the present invention; Figure 3 This is an appearance diagram of the dual-network conductive hydrogel prepared in Example 1 of the present invention; Figure 4 These are comparative images of the appearance of different protein solutions in Experimental Example 1 of the present invention. The left image is a myofibril protein solution, the middle image is a soy protein isolate solution, and the right image is a gelatin solution. Figure 5 These are comparative images of the gelation results of dual-network conductive hydrogels constructed based on different proteins in Experimental Example 1 of this invention. The left image shows the gelation result of the hydrogel constructed based on myofibrillar protein, the middle image shows the gelation result of the hydrogel constructed based on soy protein isolate, and the right image shows the gelation result of the hydrogel constructed based on gelatin. Figure 6 This is a comparative graph showing the effect of different myofibrillar protein solution concentrations (20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL) on the microstructure of the hydrogel in Experimental Example 3 of the present invention. The magnification of the images taken at each concentration is: (a) 5 k, (b) 2.5 k, (c) 1.5 k, and (d) 1 k. Figure 7 This is a comparison graph of the effect of different myofibrillar protein concentrations on the rheological properties of hydrogels in Experiment Example 3 of the present invention, n=3. The left graph shows the storage modulus (G') and loss modulus (G'') of hydrogels with different MP concentrations, and the right graph shows the creep recovery characteristics of hydrogels with different MP concentrations. Figure 8 This is a comparative graph showing the effect of different myofibrillar protein concentrations on the swelling and degradation properties of hydrogels in Experiment Example 4 of this invention, n=3. The left graph shows the swelling properties of hydrogels with different MP concentrations, and the right graph shows the in vitro degradation properties of hydrogels with different MP concentrations. Figure 9 This is a comparison graph of the effects of different myofibrillar protein concentrations on the mechanical properties of hydrogels in Experimental Example 5 of this invention, n=3. The left graph is the tensile stress-strain curve of the hydrogel, the middle graph is the elongation at break (EAB), and the right graph is the tensile strength (TS). Figure 10 This is a comparison graph of the effects of different myofibrillar protein concentrations on the mechanical properties of hydrogels in Experimental Example 5 of this invention, n=3. The left graph is the compressive stress-strain curve of the hydrogel, the middle graph is the elastic modulus (EM), and the right graph is the textural properties (hardness and elasticity). Figure 11 This is a comparison graph of the effects of different myofibrillar protein concentrations on the mechanical properties of hydrogels in Experimental Example 5 of this invention, n=3. The left graph is the cyclic loading-unloading curve of the hydrogel, and the right graph is the dissipated energy. Figure 12 A comparative graph showing the effect of different amounts of ionic liquid added on the cell compatibility of hydrogels in Experiment Example 6 of this invention (n=3). Figure 13 The experimental example 6 of this invention shows a comparison of the effects of different concentrations of ionic liquid on the cell compatibility of hydrogels. In this example, (a) is the cell viability graph of the blank control group (excluding hydrogel extract), (b) is the cell viability graph of hydrogels without added ionic liquid, (c) is the cell viability graph of hydrogels with 0.5 mol of ionic liquid added, (d) is the cell viability graph of hydrogels with 1.0 mol of ionic liquid added, (e) is the cell viability graph of hydrogels with 1.5 mol of ionic liquid added, and (f) is the cell viability graph of hydrogels with 2.0 mol of ionic liquid added. Figure 14 This is a biocompatibility diagram of hydrogel applied to mouse skin tissue in Experiment Example 6 of the present invention. From top to bottom, the diagram shows the blank control group, the hydrogel group without IL, and the hydrogel group with IL. The right image is a magnified view of the area within the dashed frame in the left image. Figure 15 These are the electrosensing characteristics of the hydrogel in Experimental Example 7 of this invention. The left figure shows the conductivity of the hydrogel with different ionic liquid concentrations, the middle figure shows the response-recovery time of the hydrogel (0.0~1.0 s), and the right figure shows the response-recovery time of the hydrogel (1.0~2.0 s). Figure 16 This is a graph showing the results of hydrogel application in monitoring human movement (finger, wrist, elbow, knee) in Experiment Example 8 of this invention; Figure 17 This is a graph showing the results of hydrogel application in human micro-expression (opening mouth, smiling, frowning) monitoring / swallowing monitoring in Experiment Example 8 of this invention; Figure 18 This is a diagram showing the results of applying hydrogel to speech recognition (ABCD, NJAU, Hello, Happybirthday) in Experiment Example 8 of this invention. Figure 19 This is a diagram showing the results of applying hydrogel to the writing and recognition of lowercase letters a to l in Experiment Example 8 of this invention; Figure 20 This is a diagram showing the results of applying hydrogel to the writing and recognition of lowercase letters m to z in Experiment Example 8 of this invention; Figure 21 This is a diagram showing the results of applying hydrogel to digital handwriting recognition in Experiment Example 8 of this invention; Figure 22 This is a diagram showing the results of applying hydrogel to the writing recognition of English words (WHO and who, WHAT and what, WHERE and where, HELLO and hello) in Experiment Example 8 of this invention. Detailed Implementation

[0071] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0072] Sources of raw materials and reagents: Chicken breast was sourced from Jiangsu Yike Food Co., Ltd., and waste meat from the production line was transported to the laboratory at 4 ℃. Dextran (Dex) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. 1-Butyl-3-methylimidazolium chloride ([BMIm]Cl), sodium alginate (SA), calcium chloride (CaCl2), and sodium periodate (NaIO4) were all purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0073] Source of instruments and equipment: PD500 homogenizer, Prima Ltd., UK; MCR-301 rheometer, Anton Paar GmbH, Germany; texture analyzer, Stable Micro Systems Ltd., UK; electronic universal testing machine, Instron 5969, Instron Ltd.; digital source meter (Geely Source Meter 2450), Keithley Instruments Ltd., USA; cryo-scanning electron microscope SU8600, Hitachi Ltd., Japan.

[0074] Determination of oxidized dextran aldehyde content and oxidation degree (hydroxylamine hydrochloride method): The prepared oxidized dextran solution was freeze-dried and pulverized to obtain oxidized dextran powder. 200 mg of oxidized dextran powder was dissolved in 25 mL of hydroxylamine hydrochloride solution (0.25 mol / L) containing 3 drops of methyl orange solution (0.05 g / 100 mL). The solution was stirred at room temperature until the oxidized dextran was completely dissolved. Then, it was titrated with 0.1 mol / L sodium hydroxide solution until the solution changed from red to bright yellow. A hydroxylamine hydrochloride solution without oxidized dextran was titrated as a blank control.

[0075] The definitions and calculation methods for aldehyde content and degree of oxidation in oxidized dextran are as follows: The aldehyde content, i.e., the number of millimoles of aldehyde groups per gram of oxidized dextran, is calculated using the following formula: Aldehyde content (mmol / g) = (V1 - V0) × M / W The degree of oxidation of the aldehyde group, i.e., the number of aldehyde groups per 100 glucose units, is calculated using the following formula: Aldehyde oxidation degree (%) = (V1 - V0) × M × M w / 1000W×100 In the formula, V1 is the volume of sodium hydroxide consumed by the sample solution (mL); V0 is the volume of sodium hydroxide consumed by the blank solution (mL); M is the molar concentration of sodium hydroxide; M w W represents the weight of glucose units on the dextran chain (160); W represents the weight of oxidized dextran (g).

[0076] Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. All raw materials or instruments used are commercially available conventional products, including but not limited to those used in the embodiments of this application.

[0077] Example 1 This embodiment provides a method for preparing a dual-network conductive hydrogel based on myofibrillar protein, the specific steps of which are as follows: (1) Raw material preparation: a. Myofibrillar protein solution: After removing fat and connective tissue from chicken, the chicken is cut into pieces and minced into a paste using a meat grinder. An appropriate amount of the minced meat is mixed with a standard salt solution (0.1 mol / L KCl, 20 mmol / L K₂HPO₄ / KH₂PO₄, 2 mmol / L LEGTA, 1 mmol / L MgCl₂, pH 7.0) at a mass ratio of 1:4 and homogenized (8000 rpm, 1 min, every 20 s, intermittent, 4 ℃). The mixture is then filtered through gauze to further remove connective tissue. The filtrate is centrifuged (2000 rpm, 10 min, 4 ℃), and the precipitate is collected. The precipitate is mixed with the standard salt solution again at the aforementioned ratio, and homogenized and centrifuged again under the same conditions (i.e., treated with the standard salt solution 3 times). The precipitate is then mixed with 0.1 mol / L KCl solution at a mass ratio of 1:4 and homogenized under the aforementioned conditions (8000 rpm, 1 min, every 20 s, intermittent, 4 ℃). The myofibrillar protein (MP) was obtained by centrifuging at 2000 rpm for 1 min, with a 20 s interval, at 4 ℃, followed by 1 min. The precipitate was then collected and mixed with KCl solution in the same proportion as described above. The mixture was homogenized and centrifuged again under the same conditions. The precipitate was then collected and mixed with KCl solution in the same proportion as described above. The mixture was homogenized and centrifuged again under the same conditions. (This process was repeated three times with KCl solution) to obtain myofibrillar protein (MP). The myofibrillar protein was dissolved in PBS buffer (0.6 mol / L NaCl, 20 mmol / L K2HPO4 / KH2PO4, pH 7.0), and the protein concentration in the solution was determined using the biuret method. The final concentration of the myofibrillar protein solution was standardized to 40 mg / mL. b. Oxidized dextran solution: Dissolve 5 g of dextran (molecular weight 70 kDa) in 100 mL of deionized water. After complete dissolution, add an appropriate amount of sodium periodate (molar ratio of dextran to sodium periodate is 1:1). React under light-protected conditions for 24 h. After the reaction is complete, add an appropriate amount of ethylene glycol (molar ratio of sodium periodate to ethylene glycol is 1:1) to terminate the reaction. Dialyze the product obtained after the reaction in deionized water for 48 h (molecular weight cutoff of dialysis bag MwCO = 3500 Da). After dialysis, take the solution from the dialysis bag to obtain the oxidized dextran solution (concentration of 20 mg / mL). The oxidation degree of oxidized dextran in the oxidized dextran solution was determined to be 90.23% by hydroxylamine titration, and the aldehyde content was 5.67 nmol / g. c. Sodium alginate solution: Dissolve 3 g of sodium alginate powder in 100 mL of deionized water to obtain the solution; d. Calcium chloride solution: Dissolve 2 g of calcium chloride in 100 mL of deionized water to obtain the solution; (2) Preparation of hydrogel: S1. Mix 30 mL of myofibrillar protein solution and 3 mL of oxidized dextran solution, and stir magnetically at 1000 rpm for 10 min to obtain mixture 1 (the mass ratio of myofibrillar protein to oxidized dextran in mixture 1 is 20:1). S2. Add 10 mL of sodium alginate solution to mixture 1, stir magnetically at 1000 rpm for 10 min, then add 1 mol of 1-butyl-3-methylimidazolium chloride and disperse evenly to obtain mixture 2; S3. Centrifuge the mixture 2 at 500 rpm for 3 min to remove air bubbles, incubate at 55 ℃ for 3 h, cool and solidify, and immerse in 20 mL of calcium chloride solution for ionic cross-linking for 3 h to obtain a double-network conductive hydrogel.

[0078] The changes in the state of the system before and after gelation are as follows: Figure 2 As shown, the system state transitions from a fluid state to a gel solid state before incubation at 55 ℃ and after cooling and solidification. The final hydrogel was cut into 2.5 mm thick hydrogel sheets, and their appearance in normal, folded, and rolled states is as follows. Figure 3 As shown, the hydrogel exhibits good elasticity, toughness, and flexibility.

[0079] Example 2 This embodiment provides a method for fabricating a flexible sensor, the specific steps of which are as follows: The dual-network conductive hydrogel prepared according to Example 1 was cut into 50 mm × 20 mm × 2 mm sheets, and the upper and lower surfaces were attached with two strips of 3M VHB tape, exposing the two ends along the length. The two ends were fixed with thin copper sheets of 50 mm × 50 mm × 1 mm and small copper clips to form electrode contact points. Each end was connected with a 0.1 mm diameter conductive copper wire as a conductor, and the two ends were assembled into a flexible sensor.

[0080] Example 3 This embodiment provides a method for preparing a handwriting recognition sensor, the specific steps of which are as follows: Commercially available polydimethylsiloxane (PDMS) film was cut to a size of 10 cm long × 5 cm wide to serve as the flexible substrate and encapsulation layer of the device. The dual-network conductive hydrogel prepared according to Example 1 was cut into a cuboid of 12 cm × 5 cm × 2.5 mm. The hydrogel was placed between two PDMS films to assemble a sandwich structure, exposing the two ends along the length direction. The two ends were fixed with thin copper sheets of 50 mm × 50 mm × 1 mm and small copper clips to form electrode contact points. Each end was connected to a conductive copper wire with a diameter of 0.1 mm as a conductor to assemble a writing recognition sensor.

[0081] Experimental Example 1 I. Experimental Objective This experimental example aims to compare the gelation effects of dual-network conductive hydrogels based on different proteins.

[0082] II. Experimental Methods Myofibrillar protein, soy protein isolate, and gelatin were dissolved in PBS buffer to prepare homogeneous protein solutions with a protein concentration of 40 mg / mL. Figure 4 As shown, the myofibrillar protein solution is milky white, the soy protein isolate solution is light yellow, and the gelatin solution is transparent.

[0083] Referring to steps S1-S3 in Example 1, hydrogels were prepared using myofibrillar protein solution, soy protein isolate solution, and gelatin solution, respectively. The gelation results are as follows: Figure 5 As shown.

[0084] III. Results Analysis like Figure 5 As shown, myofibrillar protein can form a stable hydrogel sample. Replacing it with soy protein isolate results in a non-uniform layered system with a tofu-like appearance. Replacing it with gelatin results in a light yellow flowing liquid that also cannot form a gel.

[0085] It is evident that in the same protein-polysaccharide-ionic liquid gelation system, replacing myofibrillar protein with other common plant-derived proteins (soy protein isolate) and animal-derived proteins (gelatin) prevents the formation of gels. The reasons are analyzed as follows: First, myofibrillar protein (MP) is rich in active amino groups (-NH2), and its native conformation exposes more reactive sites in the dissolved state, enabling it to undergo efficient and complete Schiff base reactions with the aldehyde groups of oxidized dextran (ODex), forming a dense and uniform first-order covalent cross-linked network. Second, MP possesses unique thermal aggregation properties; at 55 °C, its protein molecules can unfold, aggregate, and form a stable three-dimensional network, which synergistically strengthens the overall structure with the first-order chemical network. Finally, the introduction of sodium alginate (SA) and CaCl2 as a second-order cross-linked network, in a gelation system synergistically combining dual cross-linking (Schiff base reaction and ionic cross-linking) and thermal induction, makes MP, due to its high reactivity, unique thermal aggregation properties, and good system compatibility, crucial for forming a robust and uniform double-network hydrogel. Replacing it with gelatin or soy protein isolate resulted in gelation failure. Therefore, this further demonstrates the irreplaceable nature of MP-based double-network hydrogels in terms of raw material selection; MP exhibits significantly superior gelation effects in this system, resulting in a unique double-network hydrogel.

[0086] Experiment Example 2 I. Experimental Objective This experimental example aims to compare the adaptability of different ionic liquids in dual-network conductive hydrogels.

[0087] II. Experimental Methods Based on the preparation method provided in Example 1, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-propenyl-3-methylimidazolium chloride were used as conductive fillers, and their solubility and compatibility with the hydrogel system were studied.

[0088] III. Results Analysis Table 1 Comparison of the effects of different ionic liquids

[0089] As shown in Table 1, this experimental example compares the adaptability of three ionic liquids in the dual-network conductive hydrogel system constructed in this invention. Among them, 1-ethyl-3-methylimidazolium chloride and 1-propenyl-3-methylimidazolium chloride undergo phase separation with the hydrogel matrix, thus failing to achieve stable and strong conductivity. However, 1-butyl-3-methylimidazolium chloride has good compatibility with the hydrogel matrix based on myofibrillar protein and polysaccharides constructed in this invention, and can be used as a conductive filler for the dual-network conductive hydrogel, thereby preparing hydrogel samples with unique texture and functional properties.

[0090] Experimental Example 3 I. Effects of different myofibrillar protein concentrations on the microstructure of hydrogels 1. Experimental Samples Following step a in Example 1, myofibrillar protein solutions of different protein concentrations (20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL) were prepared. Further following Example 1, a dual-network conductive hydrogel was prepared using myofibrillar protein solutions of different protein concentrations.

[0091] 2. Experimental Methods The gel sample was cut into 3 mm thick cubes and fixed at 4 °C with glutaraldehyde solution (2.5 g / 100 mL) for 48 h. Then, it was dehydrated in a gradient with different volume concentrations of ethanol (50%, 70%, 90%, 100%) (10 min for each concentration) and critical point dried with CO2. Finally, the sample was fixed with conductive adhesive on a circular metal sample stage and sputtered with gold (10 mA, 300 s). The microstructure of the gel sample was photographed sequentially under high vacuum with an accelerating voltage of 5 kV and magnifications of 5 k, 2.5 k, 1.5 k, and 1 k.

[0092] 3. Results Analysis like Figure 6As shown, the cross-sectional morphology of the hydrogel was characterized by cryo-scanning electron microscopy (Cyro-SEM). The results showed that the hydrogel exhibited a uniformly distributed three-dimensional network pore structure with a pore size of approximately 2–5 µm. This three-dimensional porous network structure, serving as the framework of the myofibrillar protein hydrogel, plays a decisive role in the material's stability. It not only provides swelling properties for the storage of ionic liquids but also offers ion channels for the migration and conduction of ionic liquids.

[0093] As the MP concentration increases, the hydrogel network structure becomes denser. This is likely due to the increased polymer chain density with increasing protein content, enhanced covalent cross-linking with oxidized dextran, decreased internal water content of the hydrogel, resulting in smaller ice crystals and an increased number of pores per unit area. However, at higher concentrations, the MP solution becomes too viscous, resulting in poor flowability, which is detrimental to uniform mixing, cross-linking, and subsequent gel formation.

[0094] II. Effects of Different Myofibrillar Protein Concentrations on the Rheological Properties of Hydrogels 1. Experimental Samples Following step a in Example 1, myofibrillar protein solutions of different protein concentrations (20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL) were prepared. Further following Example 1, a dual-network conductive hydrogel was prepared using myofibrillar protein solutions of different protein concentrations.

[0095] 2. Experimental Methods The viscoelasticity and creep-recovery properties of the gel samples from each treatment group were measured using a rheometer. The rheometer temperature was set to 25 ℃, and the frequency scanning measurement parameters were as follows: the measuring probe was PP / 25, the gap between the probe and the plate was 5 mm, and the strain was 0.1% (within the linear viscoelastic range). The changes in the storage modulus (G') and loss modulus (G") of the gel within the range of 0.01 Hz to 10 Hz were recorded. The creep-recovery measurement parameters were as follows: the measuring probe was PP / 25, the gap between the probe and the plate was 5 mm, and during the creep process, a constant stress of 7 Pa (within the linear viscoelastic range) was applied to the gel and maintained for 180 s. After the stress was removed, the gel was observed for 300 s.

[0096] 3. Results Analysis Storage modulus (G′) and loss modulus (G″) are two important parameters for evaluating hydrogel networks. G′ measures the energy elastically stored in the gel structure during periodically applied stress and can be used to characterize the elastic properties of the gel; while G″ measures the viscous characteristics. Figure 7As shown on the left, the G′ value is consistently greater than the corresponding G″ value across the entire frequency scan range, indicating that all hydrogel samples exhibit elastic, solid-like characteristics rather than viscous sols. The results show that with increasing MP concentration, the G′ and G″ values ​​of the hydrogel also increase, indicating a denser internal network and a more stable structure, effectively enhancing the hydrogel's mechanical properties. These micro-rheological results are consistent with the mechanical property test results described later, confirming the excellent mechanical properties of the dual-network hydrogel from a microscopic perspective.

[0097] A creep-recovery test with small strain was used to evaluate its hardness and recovery ability after being subjected to external forces. For example... Figure 7 As shown on the right, when the gel is subjected to a constant stress (7 Pa, within the linear viscoelastic range), the strain values ​​of all gels increase rapidly, followed by a gradual decrease in the rate of strain increase (creep stage). When the pressure applied to the gel is suddenly removed, the strain value gradually decreases until a constant strain value is reached (recovery stage). The maximum value of the creep curve reflects the hardness of the sample; the larger the strain value, the softer the sample, and vice versa. When the MP concentration is 20 mg / mL, the gel exhibits a low strain value, which may be because the protein concentration in the system is low at this time, resulting in fewer amino groups that can react with the ODex aldehyde groups, thus leading to lower gel strength. As the MP concentration increases, the gel exhibits a strain value that first increases and then decreases, indicating that a higher MP concentration enhances the hardness of the gel. This may be due to the increased density of the MP polymer chains, and the enhanced crosslinking between ODex and MP strengthens the gel network system. However, at higher concentrations, the dense structure of the hydrogel makes it harder, prone to brittle fracture under external pressure, and exhibits poor mechanical properties.

[0098] Experiment Example 4 Effects of different myofibrillar protein concentrations on the swelling and degradation properties of hydrogels 1. Experimental Samples Following step a in Example 1, myofibrillar protein solutions of different protein concentrations (20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL) were prepared. Further following Example 1, a dual-network conductive hydrogel was prepared using myofibrillar protein solutions of different protein concentrations.

[0099] 2. Experimental Methods Gel samples from each treatment group were cut into cylinders with a diameter of 2.5 cm and a height of 1 cm, and their initial weights were recorded. The gel samples were placed in PBS buffer, and the gels were removed every 1 hour, blotted dry, and weighed until the difference between two weighings was less than 0.1 g. The gel swelling ratio was calculated using the following formula:

[0100] In the formula, M is the final mass of the gel (g) when the mass difference is less than 0.1 g; M0 is the initial mass of the gel (g).

[0101] The initial mass of the gels at swelling equilibrium was used as the initial mass. Gels from each treatment group were placed in PBS buffer, and the gels were removed and weighed after drying the surface moisture every day. This was repeated for two weeks. The in vitro degradation rate of the gels was calculated using the following formula:

[0102] In the formula, M t The mass of the gel (g) was measured for the experiment; M1 is the initial mass of the gel (g).

[0103] 3. Results Analysis Depend on Figure 8 (Left) As can be seen, with the increase of MP concentration, the swelling of the hydrogel first increases and then decreases, and all curves show a trend of first increasing and then leveling off with swelling time. This indicates that the hydrogel is hydrophilic, and its abundant porous structure is conducive to material exchange, enabling it to absorb a large amount of water without dissolving, thus exhibiting good swelling performance. When swelling begins, the hydrogel can rapidly absorb water, and the swelling rate increases sharply. When a certain time is reached, the exchange of water molecules within the network reaches equilibrium, the swelling capacity is limited, and the swelling rate gradually tends to equilibrium. The maximum swelling ratio of this gel in PBS buffer can reach 7.04 times, while higher concentrations of MP enhance the crosslinking density between MP and ODex, resulting in a smaller pore size, reduced water absorption, and a decreased swelling rate, which is consistent with the SEM microscopic results. Furthermore, ODex contains a large number of hydrophilic groups (-CHO), which to some extent enhances the gel's ability to bind with water.

[0104] Once the gel reached swelling equilibrium, its in vitro degradation characteristics were investigated. The changes in gel mass during the experiment are as follows: Figure 8 As shown on the right, the gels degraded to varying degrees within 1 to 11 days. Rapid degradation occurred between days 2 and 7, followed by a gradual decrease in degradation rate, with the highest in vitro degradation rate reaching 80.5%. The degradation rate decreased with increasing MP and ODex cross-linking degree, indicating that increasing the cross-linking degree can delay gel degradation. The 30 mg / mL protein hydrogel exhibited a lower degradation rate, which may be due to its denser gel network structure, enhancing its mechanical strength.

[0105] Experimental Example 5 Effect of different myofibrillar protein concentrations on the mechanical properties of hydrogels 1. Experimental Samples Following step a in Example 1, myofibrillar protein solutions of different protein concentrations (20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL) were prepared. Further following Example 1, a dual-network conductive hydrogel was prepared using myofibrillar protein solutions of different protein concentrations.

[0106] 2. Experimental Methods The tensile properties of hydrogel samples were tested according to the national standard GB / T 528-2009. The hydrogel was cut into cubes of 50 mm × 5 mm × 2 mm, and the tensile rate was 100 mm / min. Each sample was tested 5 times, and the average value was used for calculation.

[0107] The fatigue resistance of hydrogels was evaluated using a tensile-restorative-tensile test. A universal testing machine was used to fix both ends of the hydrogel, limiting the tensile range to 5% deformation from the initial position, and the hydrogel's fatigue resistance was evaluated by repeated tensile tests 10 times.

[0108] Tensile strength (σ) and elongation at break (ε) are calculated according to the following formula:

[0109]

[0110] In the formula, σ is the tensile strength (kPa); F is the maximum load (N) experienced by the specimen before fracture; and A0 is the cross-sectional area of ​​the specimen (mm²). 2 ); ε is the elongation at break (%); L is the length of the specimen at break (mm); L0 is the original length of the specimen (mm).

[0111] The compressibility of the hydrogels was tested using an electronic universal testing machine at room temperature. A cylinder with a diameter of 3 cm and a height of 4 cm was formed and placed under a compression clamp for testing at a compression rate of 10 mm / min. Compressive strain was defined as the ratio of the compressed height to the initial height. Compressive strength was defined as the ratio of compressive stress to the cross-sectional area of ​​the sample. Toughness was the area enclosed by the compressive strength-compressive strain curve. Energy dissipation was the area enclosed by the loading / unloading curve.

[0112]

[0113] In the formula, p is the compressive strain (%); H is the height of the hydrogel after compression (mm); H0 is the initial height of the hydrogel before compression (mm).

[0114] 3. Results Analysis The tensile stress-strain curve of the hydrogel and the corresponding elongation at break (EAB) and tensile strength (TS) are as follows: Figure 9As shown, the tensile strength and elongation at break of the hydrogel both increased with increasing concentration. Specifically, the tensile strength increased from 0.163 ± 0.018 MPa to 0.321 ± 0.024 MPa, while the elongation at break increased from (32.64 ± 12.21)% to (63.01 ± 16.46)%. This is likely due to the enhanced Schiff base crosslinking reaction between the amino groups of MP and the aldehyde groups of ODex with increasing MP concentration. Furthermore, the ionic bonds between SA and CaCl2 further increased the entanglement and crosslinking degree between the hydrogel molecular chains. This is consistent with the results shown in the SEM images.

[0115] like Figure 10 As shown, when the MP concentration increased from 20 mg / mL to 50 mg / mL, the compressive strength of the gel increased from 0.36±0.05 MPa to 0.52±0.05 MPa, while the corresponding compressive modulus decreased from 0.87±0.09 MPa to 0.16±0.27 MPa. Furthermore, the texture analysis results indicated that the gel's hardness remained at a moderate level, with the increase in MP concentration leading to an increase in gel hardness. Elasticity refers to the gel's ability to deform under external force; the results showed that increasing the MP content slightly increased the gel's elasticity; the gels maintained a high level of elasticity throughout.

[0116] like Figure 11 As shown, the gel exhibits a maximum stress of 0.57 MPa in the load-unload cycle test, with rapid recovery and a short hysteresis period, demonstrating good elasticity.

[0117] In summary, gels with different protein contents all exhibited good mechanical properties, and the mechanical properties were significantly enhanced with the increase of MP content.

[0118] Experimental Example 6 I. Effects of different ionic liquid concentrations on the cell compatibility of hydrogels 1. Experimental Samples Hydrogel samples with ionic liquid contents of 0 mol, 0.5 mol, 1.0 mol, 1.5 mol, and 2.0 mol were prepared according to Example 1. After freeze-drying, the prepared hydrogel samples were sterilized by UV irradiation for 30 min, and then soaked in sterile PBS buffer for 2 h. Next, the hydrogels were soaked in high-glucose DMEM medium solution (containing 10% fetal bovine serum, 100 mmol / L penicillin, and 100 μg / mL streptomycin) at a ratio of 1:10 for 72 h. After filtration (0.2 µm), the extracts of the hydrogels were obtained and labeled as IL-0 (ionic liquid content of 0 mol), IL-1 (ionic liquid content of 0.5 mol), IL-2 (ionic liquid content of 1.0 mol), IL-3 (ionic liquid content of 1.5 mol), and IL-4 (ionic liquid content of 2.0 mol).

[0119] 2. Experimental Methods Mouse fibroblasts (L929) were used for in vitro cytotoxicity evaluation. Cells were cultured in high-glucose DMEM medium (37 ℃, 5% CO2, 100% humidity) containing 10% fetal bovine serum (FBS) and antibiotics (100 U / mL penicillin and 100 μg / mL streptococcal mycin) for at least 24 h. When the cells covered 75%–85% of the 96-well plates, the complete medium was replaced with hydrogel extracts containing different amounts of ionic liquid (0.5 mol, 1.0 mol, 1.5 mol, 2.0 mol). After culturing for another 24 h, the OD value of the cells at 450 nm was measured using the CCK-8 assay. A hydrogel extract without ionic liquid (0 mol ionic liquid) served as the control group, and pure serum-free high-glucose medium solution served as the blank group. OD values ​​were measured under the same conditions, and cell viability was calculated using the following formula:

[0120] 3. Results Analysis In this experiment, L929 mouse fibroblast epithelial cells were selected, and the cell compatibility of the hydrogel was evaluated by co-culturing the hydrogel extract with the cells for 24 h.

[0121] like Figure 12 As shown, without the addition of ionic liquid, cell viability is close to 100%. This result indicates that the hydrogel has good biocompatibility, which may be due to the proteins and lipids in the hydrogel providing additional nutrients for cell growth, thus maintaining a high cell proliferation rate. Even after adding different amounts of ionic liquid, the cell viability remained above the critical threshold of 70%, demonstrating the hydrogel's good cell compatibility.

[0122] like Figure 13 As shown, the cell morphology of the experimental group and the control group was observed after 24 h of culture. It was found that the cells in both groups had typical spindle-shaped or fusiform fibroblast morphology and grew normally adherently, indicating that the cells were not affected.

[0123] II. Effects of hydrogels on the biocompatibility of mouse skin tissue 1. Experimental Samples Hydrogel without IL: Hydrogel samples were prepared according to Example 1, without adding ionic liquids during the preparation process; Hydrogel with added IL: Hydrogel samples were prepared according to Example 1.

[0124] 2. Experimental Methods Animal experiments were conducted in accordance with NIH guidelines for laboratory animal care and euthanasia, the requirements of the Animal Research Committee of the National Center for Nanoscience and Technology, and the protocol approved by the Institutional Animal Care (NCNST-LX-2309-03). Female BALB / c mice (6–8 weeks old) were selected for animal experiments. First, mice were randomly divided into three groups (hydrogel treatment group without IL, hydrogel treatment group with IL, and blank control group) and anesthetized with 2% isoflurane. Then, the backs of the mice were shaved. In the hydrogel treatment group without IL, a hydrogel sample (25 mm × 25 mm × 2.5 mm) was fixed to the back of the mouse with tape. In the hydrogel treatment group with IL, a hydrogel sample (25 mm × 25 mm × 2.5 mm) was fixed to the back of the mouse with tape. The blank control group was shaved only on the back and had no hydrogel sample attached. All mice were incubated at room temperature of 25 °C for 48 h. Finally, the mice were observed to see if there was an allergic reaction on the skin near the hydrogel. The tissue around the area was collected, fixed in 10% formalin, dehydrated, immersed in xylene for 30 min, embedded in paraffin to make sections, and fixed on glass slides. Then, hematoxylin and eosin (H&E) staining was used to analyze the tissue inflammation caused by the two groups of hydrogel samples.

[0125] 3. Results Analysis No obvious allergic reactions or other adverse reactions were observed in the mice's skin within 48 hours. Figure 14 As shown, the H&E staining results did not reveal vacuolation or obvious inflammatory cells, indicating that the hydrogel has good biocompatibility and can be adhered to the skin for physiological signal detection.

[0126] Experimental Example 7 Effect of different ionic liquid concentrations on the electrosensing properties of hydrogels 1. Experimental groups and samples Hydrogel samples were prepared according to Example 1, with ionic liquid (IL) addition amounts of 0.0 mol, 0.2 mol, 0.4 mol, 0.6 mol, 0.8 mol, and 1.0 mol, respectively.

[0127] 2. Experimental Methods The hydrogel sample was cut into 50mm × 20mm × 2mm sheets, and its top and bottom surfaces were secured with two strips of 3M VHB tape to prevent moisture evaporation. The two ends along its length were exposed and fixed to each end with a 50mm × 50mm × 1mm thin copper sheet and a small copper clip to form electrode contact points. A 0.1mm diameter conductive copper wire was connected to each end, assembling a flexible sensor. The conductivity of the hydrogel sample was tested using a digital source meter, and the ionic conductivity was calculated using the following formula:

[0128] In the formula, σ is the ionic conductivity (S / cm); L is the sample thickness (2 mm); and A is the sample cross-sectional area (mm²). 2 R is the resistance (Ω).

[0129] 3. Results Analysis like Figure 15 As shown, the conductivity of the hydrogel gradually increases with the increase of the amount of ionic liquid added. This is due to the increase in the content of freely moving anions and cations in the three-dimensional network structure of the hydrogel. In addition, the response-recovery time diagram of the hydrogel (1.0 mol of ionic liquid added) shows that the hydrogel can achieve rapid response recovery within 0.6 s.

[0130] Experimental Example 8 I. Experimental Objective The application effects of the flexible sensor prepared in Example 2 in human motion monitoring, human facial micro-expression monitoring, and speech recognition were verified, as well as the application effects of the flexible sensor prepared in Example 3 in handwriting recognition.

[0131] II. Experimental Methods 1. Human motion monitoring The sensors prepared in Example 2 were applied to different parts of the volunteers' bodies (finger joints, wrist joints, elbow joints, and knee joints). The wires at both ends of the sensors were connected to a digital source meter, and the voltage was set to 5 V. The relative resistance change of the sensors was recorded in real time when each joint was bent.

[0132] 2. Human facial micro-expression / swallowing monitoring The sensors prepared in Example 2 were applied to designated areas on the volunteers' faces or necks (smile monitoring: chin; swallowing monitoring: neck and throat; frown monitoring: center of the forehead; mouth opening monitoring: chin). The wires at both ends of the sensors were connected to a digital source meter, and the voltage was set to 5 V. The relative resistance changes of the sensors during micro-expression changes / swallowing were recorded in real time.

[0133] 3. Speech recognition The sensors prepared in Example 2 were applied to the neck and throat of volunteers. The wires at both ends of the sensors were connected to a digital source meter, and the voltage was set to 5 V. The volunteers spoke the set words or sentences, and the relative resistance change of the sensors was recorded in real time during the pronunciation.

[0134] 4. Handwriting recognition The sensor prepared in Example 3 was used as a writing pad. The wires at both ends of the sensor were connected to a digital source meter, and the voltage was set to 5 V. Volunteers wrote the set letters, numbers or words on the writing pad, and the relative resistance change of the sensor was recorded in real time during the writing process.

[0135] illustrate: All participants in the electronic skin sensor experiment signed informed consent forms.

[0136] Relative resistance is calculated using the following formula:

[0137] In the formula, R0 and R represent the corresponding resistance values ​​before and after the motion.

[0138] III. Results Analysis The flexible sensor based on this dual-network conductive hydrogel provided by the present invention has the advantages of reliability, sensitivity and stability.

[0139] like Figure 16 As shown, the flexible sensor provided by this invention can monitor human limb movements in real time.

[0140] like Figure 17 As shown, in addition to monitoring large movements of the human body, this flexible sensor can also monitor tiny and complex muscle movements during swallowing and vocalization. When volunteers perform periodic swallowing movements, a clear and relatively consistent resistance change pattern is observed. In addition, the sensor can also accurately monitor changes in human micro-expressions, such as smiling, frowning, and opening the mouth.

[0141] like Figure 18 As shown, when the volunteer said the word "Hello," the sensor exhibited a sensitive signal in terms of relative resistance change. Furthermore, the sensor displayed distinguishable resistance signals when pronouncing different words, indicating that the sensor's output resistance signal changes with the word.

[0142] Figures 19-22 The results show that the sensor can not only stably monitor human movement and capture speech sounds, but it can also be used in the writing sensing process, exhibiting different electrical signal responses when writing different letters, numbers, and words.

[0143] Therefore, the dual-network conductive hydrogel provided by this invention is expected to be used in wearable sensors, voice and handwriting recognition systems, etc.

[0144] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a dual-network conductive hydrogel based on myofibrillar protein, characterized in that, Includes the following steps: S1. Mix the myofibrillar protein solution and the oxidized dextran solution evenly to obtain mixture 1; S2. Mix the mixture 1 with sodium alginate solution and 1-butyl-3-methylimidazolium chloride to obtain mixture 2. S3. The mixture 2 is heated, cooled and shaped, and then immersed in calcium chloride solution for ionic cross-linking to obtain a double-network conductive hydrogel.

2. The method for preparing the myofibrillar protein-based dual-network conductive hydrogel according to claim 1, characterized in that, Step S1 satisfies at least one of the following conditions: 1) The myofibrillar protein solution is obtained by dissolving myofibrillar protein in PBS buffer, and the composition of the PBS buffer is as follows: 0.6 mol / L NaCl, 20 mmol / L K2HPO4 / KH2PO4, pH 7.0; 2) The protein concentration in the myofibrillar protein solution is 20~50 mg / mL; 3) The concentration of the oxidized dextran solution is 20~25 mg / mL; 4) The oxidized dextran solution is prepared by sodium periodate oxidation method; 5) The degree of oxidation of the oxidized dextran in the oxidized dextran solution is 90.23 ± 0.96%; 6) The aldehyde content of the oxidized dextran in the oxidized dextran solution is 5.67 ± 0.08 nmol / g; 7) The mass ratio of myofibrillar protein to oxidized dextran in the mixture 1 is 5~20:1; 8) Mixing conditions: Stir at 800~1500 rpm for 10~15 min; And / or, step S2 satisfies at least one of the following conditions: 1) The concentration of the sodium alginate solution is 25~30 mg / mL; 2) The volume ratio of the sodium alginate solution to the myofibrillar protein solution is 1:2~5; 3) The mixing conditions are as follows: Mix the above-mentioned mixture 1 with sodium alginate solution and stir at 800~1500 rpm for 10~15 min, then add 1-butyl-3-methylimidazolium chloride and disperse evenly; 4) The molar volume ratio of the 1-butyl-3-methylimidazolium chloride to the myofibrillar protein solution is not greater than 1:30 mol / mL; And / or, step S3 satisfies at least one of the following conditions: 1) The heating temperature is 50~55℃; 2) Heating time is 2.5~3.5 h; 3) The concentration of the calcium chloride solution is 10~30 mg / mL; 4) The ratio of the sum of the volumes of the mixture 1 and the sodium alginate solution to the volume of the calcium chloride solution is 1~3:1; 5) Soaking time is 2-4 hours; 6) Before the heat treatment, the mixture 2 is centrifuged at 300-500 rpm for 3-5 min to remove air bubbles.

3. The method for preparing the myofibrillar protein-based dual-network conductive hydrogel according to claim 1, characterized in that, At least one of the following conditions must be met: 1) The method for preparing myofibrillar protein in the myofibrillar protein solution includes the following steps: mincing chicken meat after removing fat and connective tissue; mixing the minced meat with a standard salt solution and homogenizing, centrifuging to collect the precipitate; mixing the precipitate with KCl solution and homogenizing, centrifuging to collect the precipitate, thereby obtaining the myofibrillar protein; 2) The preparation method of the oxidized dextran solution includes the following steps: dissolving dextran in deionized water, adding sodium periodate, reacting under light-protected conditions, and after the reaction is complete, adding ethylene glycol to the reaction solution to terminate the reaction, and dialysis the product obtained after the reaction in deionized water. After dialysis, collecting the solution in the dialysis bag, the oxidized dextran solution is obtained.

4. The method for preparing the myofibrillar protein-based dual-network conductive hydrogel according to claim 3, characterized in that, The method for preparing myofibrillar protein satisfies at least one of the following conditions: 1) The mass ratio of the minced meat to the standard salt solution is 1:3~5; 2) The composition of the standard salt solution is as follows: 0.1 mol / L KCl, 20 mmol / L K2HPO4 / KH2PO4, 2 mmol / LEGTA, 1 mmol / L MgCl2, pH 7.0; 3) Repeat the process of adding standard salt solution, mixing, homogenizing, and centrifuging to collect the precipitate 1-3 times; 4) The mass ratio of the precipitate to the KCl solution is 1:3~5; 5) The concentration of the KCl solution is 0.1~0.2 mol / L; 6) Repeat the process of adding KCl solution, mixing, homogenizing, and centrifuging to collect the precipitate 1-3 times; 5) Homogenization conditions: homogenize at 0~4 ℃ and 6000~8000 rpm for 1~2 min, with a break every 20~30 s. 6) Centrifugation conditions: 0~4 ℃, 2000~5000 rpm for 10~15 min; And / or, in the method for preparing the oxidized dextran solution, at least one of the following conditions is met: 1) The mass-to-volume ratio of the dextran to the deionized water is 4-5 g: 100 mL; 2) The molecular weight of the dextran is 60~70kDa; 3) The molar ratio of the dextran, the sodium periodate, and the ethylene glycol is 1:1:1; 4) The reaction time is 20-30 hours; 5) The molecular weight cutoff of the dialysis bag is 3000~4000 Da; 6) Dialysis time is 40-50 hours.

5. The myofibrillar protein-based dual-network conductive hydrogel obtained by the preparation method according to any one of claims 1 to 4.

6. The application of the myofibrillar protein-based dual-network conductive hydrogel obtained by the preparation method according to any one of claims 1 to 4 in the preparation of flexible sensors.

7. A flexible sensor, characterized in that, The invention includes the dual-network conductive hydrogel based on myofibrillar protein obtained by the preparation method according to any one of claims 1 to 4.

8. The method for fabricating the flexible sensor according to claim 7, characterized in that, Includes the following steps: The myofibril-based dual-network conductive hydrogel is cut into hydrogel sheets; pressure-sensitive adhesive tape or flexible film is attached to the upper and lower surfaces of the hydrogel sheets, exposing both ends of the hydrogel sheets; conductive metal sheets are clamped at the exposed ends of the hydrogel sheets, and wires are connected to the conductive metal sheets at both ends.

9. The method for fabricating a flexible sensor according to claim 8, characterized in that, At least one of the following conditions must be met: 1) The pressure-sensitive tape is a 3M VHB tape; 2) The flexible film is a polydimethylsiloxane film; 3) The thickness of the hydrogel sheet is 2~3 mm; 4) The conductive metal sheet is a soft copper sheet; 5) Connect the wires at both ends of the hydrogel sheet to a digital source meter to test the real-time resistance change curve over time; the voltage of the digital source meter is set to 4~5 V.

10. The application of the flexible sensor according to claim 7 or the flexible sensor obtained by the preparation method according to claim 8 or 9 in the preparation of human motion monitoring sensors, micro-expression monitoring sensors, speech recognition sensors or handwriting recognition sensors.

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