Fibroin-based anti-freezing conductive double-network hydrogel, preparation method and application thereof

Abstract

The application provides a silk fibroin-based anti-freezing conductive double-network hydrogel and a preparation method and application thereof. The preparation method comprises the following steps: dissolving degummed silk in a lithium bromide solution, then adding a conductive substance and uniformly mixing, and one-step cross-linking under the action of a cross-linking agent to form a silk fibroin conductive hydrogel. The silk fibroin and the conductive substance can form cross-linked networks under the action of the cross-linking agent, in addition, there is intermolecular force between the silk fibroin and the conductive substance, which is helpful to the anchoring effect of the conductive substance in the gel matrix. The high-concentration ions and the conductive network in the gel act as a conductive medium to promote the sensing sensitivity and stability of the conductive hydrogel. The formation of the double network obviously reduces the freezing point of the gel system. The hydrogel prepared by the application has good mechanical properties, conductive sensing properties and ultrafast response / recovery time in an ultra-low temperature environment, and is suitable for fields such as human motion monitoring in polar exploration activities and the like.

Description

Technical Field

[0001] This invention relates to the field of conductive hydrogel technology, specifically to an antifreeze conductive dual-network hydrogel based on silk fibroin, its preparation method, and its application. Background Technology

[0002] Conductive hydrogels, as a type of functional hydrogel, possess excellent mechanical and electrical properties, and can accurately convert external mechanical stimuli into recordable electrochemical signals, showing great promise for the fabrication of flexible electronic devices. However, under harsh environments, especially ultra-low temperature conditions, the water molecules in conductive hydrogel materials can freeze. The brittleness of the gel leads to a significant decrease or even complete loss of its mechanical flexibility and sensing performance. Therefore, developing conductive hydrogels with excellent antifreeze properties in ultra-low temperature environments is of great significance.

[0003] In recent years, incorporating inorganic salts or ionic liquids into hydrogel matrices has proven to be an effective way to integrate excellent conductivity and antifreeze properties. These ions can interact strongly with water molecules to form hydrated ions, lowering the freezing point of water and thus improving the antifreeze properties of the hydrogel.

[0004] Silk fibroin is a natural high-molecular-weight fibrous protein rich in β-sheet crystalline structures. Regenerated silk fibroin is widely used in the preparation of conductive hydrogels due to its excellent biocompatibility, mechanical toughness, and biodegradability. Furthermore, the mechanical properties and degradation performance of the gel can be effectively adjusted through secondary structure to meet different practical needs. Existing antifreeze conductive hydrogels derived from SF are mainly achieved by introducing ions and organic solvents.

[0005] Patent CN115093711 A discloses a method for preparing an antifreeze conductive hydrogel made from silk fibroin. The method utilizes silk fibroin, acrylamide, polyethyleneimine, lithium chloride, N,N-methylenebisacrylamide, and ammonium persulfate to prepare a silk fibroin-based hydrogel. This hydrogel exhibits antifreeze properties, as well as adhesion and conductivity, making it suitable for applications in biomedicine and electronic devices. Patent CN114854052 uses polyvinyl alcohol, borax, silk fibroin, and tannic acid as components. It selects a polyol / water binary solvent with good compatibility with these components and possessing an antifreeze mechanism to introduce into the hydrogel system, preparing an antifreeze conductive hydrogel made from silk fibroin. However, the entire preparation process is time-consuming, which is not conducive to industrial production applications.

[0006] A patent published in CN 115232478 A describes a silk fibroin / lithium bromide conductive hydrogel pressure sensor. This sensor, composed of a cross-linked silk fibroin network primarily composed of Silk I structure and Li+, exhibits good flexibility and electroresponsiveness. However, increasing the conductivity of ion-dependent hydrogels often sacrifices their mechanical properties [D. Ji, JMPark, MS Oh, TLNguyen, H. Shin, JSKim, D. Kim, HSPark, J. Kim, Nature Communications 2022, 13, 3019.]. Furthermore, external forces such as pressure and shear, as well as changes in the operating environment, can lead to ion displacement and leakage within the hydrogel, significantly impacting its conductive stability and lifespan. Therefore, establishing a robust cross-linked conductive network within the hydrogel is crucial.

[0007] In view of this, it is necessary to design an improved antifreeze conductive dual-network hydrogel based on silk fibroin, as well as its preparation method and application, to solve the above problems. Summary of the Invention

[0008] In view of the technical problems existing in the background art, this application provides a silk fibroin-based antifreeze conductive dual-network hydrogel, its preparation method and application. In this preparation method, silk fibroin and conductive material can each form a cross-linked network under the action of a cross-linking agent. In addition, there are intermolecular forces between silk fibroin and conductive material, which helps the conductive material to anchor in the gel matrix. The formation of the conductive material network can further improve the conductivity of the hydrogel. Moreover, the presence of ions and the synergistic effect of the dual-network structure significantly enhance the antifreeze performance of the gel. The obtained hydrogel still has good mechanical and sensitive sensing properties at -108℃.

[0009] This hydrogel features a simple preparation method, high sensitivity, and short response time. This invention provides a new approach for preparing hydrogel sensors with good ionic conductivity and mechanical properties under extreme conditions.

[0010] In a first aspect, embodiments of this application provide a method for preparing a silk fibroin-based antifreeze conductive dual-network hydrogel, comprising the following steps:

[0011] S1, Degummed silk is mixed with lithium bromide and heated to dissolve, resulting in a silk fibroin / lithium bromide blend solution;

[0012] S2, add conductive material and crosslinking agent to the silk fibroin / lithium bromide blend solution obtained in step S1 to obtain a second mixed solution; then place the second mixed solution in an oven for incubation to obtain an antifreeze conductive dual-network hydrogel based on silk fibroin.

[0013] In this embodiment, degummed silk is dissolved in a lithium bromide solution, followed by the addition of a conductive material and thorough mixing. A cross-linking agent is then used to further cross-link the mixture, forming a silk fibroin conductive hydrogel. Under the action of the cross-linking agent, the silk fibroin and the conductive material can each form a cross-linked network. Furthermore, intermolecular forces exist between the silk fibroin and the conductive material, which helps anchor the conductive material within the gel matrix. The high concentration of ions and the conductive network in the gel, acting as a conductive medium, jointly promote the sensing sensitivity and stability of the conductive hydrogel. In addition, lithium bromide disrupts the hydrogen bonds between water molecules, and the formation of the dual network significantly lowers the freezing point of the gel system. The hydrogel prepared by this invention exhibits stable and non-destructive mechanical properties, conductive sensing performance, and ultrafast response / recovery time under ultra-low temperature conditions, making it suitable for ultra-low temperature environments, such as human motion monitoring in polar expeditions and flexible robotics.

[0014] Furthermore, in step S2, the amount of the conductive material used is 0.5%-2% of the amount of silk fibroin in the silk fibroin / lithium bromide blend solution.

[0015] Furthermore, in the second mixed solution, the mass ratio of silk fibroin, conductive substance, and cross-linking agent is silk fibroin: conductive substance: cross-linking agent = 1:(0.5%-2%):(8.0-30%).

[0016] Furthermore, in step S1, the mass fraction of silk fibroin in the silk fibroin / lithium bromide blend solution is 1.0 to 10.0 wt%.

[0017] Furthermore, the concentration of the lithium bromide is 7.0-11.0 mol / L.

[0018] Furthermore, the conductive material is one or more of the following: carbon nanotubes, graphene oxide, Mxene, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate, polyimide, polyacetylene, polypyrrole, and polyaniline.

[0019] Furthermore, in step S1, during the heating and dissolution treatment, the temperature is 30–120°C, and the reaction time is 0.05–24 h. Preferably, the temperature is 45–85°C, and the reaction time is 0.3–4 h.

[0020] Furthermore, the crosslinking agent is selected from one or more of polyethylene glycol diglycidyl ether, horseradish peroxidase-H2O2, genipin, polyethylene glycol diglycidyl ether, carbodiimide, glutaraldehyde, 1,4-butanediol diglycidyl ether, tetraiodotetrachlorofluorescein, and riboflavin.

[0021] Secondly, this application provides a silk fibroin-based antifreeze conductive dual-network hydrogel, which is prepared by the aforementioned technical solution. The silk fibroin-based antifreeze conductive dual-network hydrogel has a dual-network structure, and the chemical cross-linking agent forms covalent bonds with both the silk fibroin and the conductive material to form two cross-linking networks.

[0022] The antifreeze conductive dual-network hydrogel based on silk fibroin is used in fields such as human motion monitoring, climate monitoring, and flexible robots in extremely cold weather, such as polar expeditions.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) This invention provides a method for preparing an antifreeze conductive dual-network hydrogel based on silk fibroin. Lithium bromide is used to disrupt the hydrogen bonds between water molecules in the gel, thereby preventing ice crystal formation and lowering the gel's freezing point, thus achieving antifreeze properties. A dual-network structure is constructed by cross-linking silk fibroin and a conductive material, which helps to ensure the uniform distribution and anchoring of the conductive network within the hydrogel. Furthermore, electrostatic interactions exist between the silk fibroin and the conductive material; these intermolecular forces contribute to the stability of the conductive network within the gel. Simultaneously, the dissociated Li... + , Br - The formation of ion pathways increases the conductive pathways within the gel, and the synergistic effect of these two conductive mechanisms significantly improves conductivity and the stability of sensing performance. Specifically, the addition of a cross-linking agent to chemically cross-link silk fibroin and conductive materials constructs a dual-network structure, enhancing the conductivity of the conductive hydrogel while simultaneously imparting good mechanical flexibility and conductive stability.

[0025] (2) Due to the hydrogen bond breaking ability of lithium bromide and the stability of the double network structure in the gel, the gel exhibits good antifreeze performance in the -80℃ ultra-low temperature environment. Its resistance change rate is not significantly different from that at room temperature, and it has good low temperature sensing performance.

[0026] (3) Compared with traditional silk-based conductive hydrogels, the gel prepared in this invention has superior mechanical properties and elastic recovery rate. It also boasts advantages such as high deformation sensing sensitivity, wide sensing range, and fast response speed, ensuring reliable and accurate monitoring of human movement.

[0027] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0029] Figure 1 The images show actual photos of the hydrogels prepared in Examples 1-4 and Comparative Example 1.

[0030] Figure 2 Infrared spectral images of the hydrogels prepared in Examples 1-4 and Comparative Example 1.

[0031] Figure 3 XPS spectra of PEDOT:PSS for hydrogels prepared in Examples 1-4 and Comparative Example 1 before and after BDDE treatment.

[0032] Figure 4 This is a comparison chart of the conductivity of the hydrogels prepared in Examples 1-4 and Comparative Example 1.

[0033] Figure 5 This is a photograph of the silk fibroin / lithium bromide solution that showed aggregation after the addition of a conductive substance in Comparative Example 2.

[0034] Figure 6 This is a comparison of the conductivity of the hydrogels prepared in Comparative Example 3 and Example 1 before and after desalination.

[0035] Figure 7 The graph shows the relative resistance change rate when the hydrogel prepared in Example 1 is applied to the elbow, wrist, fingers, and knee during bending cycles.

[0036] Figure 8 The DSC curve of the hydrogel prepared in Example 1 is shown.

[0037] Figure 9 The resistivity change curve of the hydrogel prepared in Example 1 under 20% strain at room temperature and -80℃ for 1000 cycles of continuous loading-unloading. Detailed Implementation

[0038] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0040] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0041] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0042] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0043] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0044] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0045] Currently, increasing the conductivity of ion-gels often sacrifices their mechanical properties. Furthermore, external forces such as pressure and shear stress, as well as changes in the usage environment, can lead to ion displacement and leakage within the gel, significantly impacting its conductive stability and lifespan. Therefore, establishing a robust cross-linked conductive network within the hydrogel is crucial.

[0046] This application provides a method for preparing a silk fibroin-based antifreeze conductive dual-network hydrogel, comprising the following steps:

[0047] S1, Degummed silk is mixed with lithium bromide and heated to dissolve, resulting in a silk fibroin / lithium bromide blend solution;

[0048] The concentration of lithium bromide is 7.0-11.0 mol / L.

[0049] During the heating and dissolution treatment, the temperature is 30–120°C, and the reaction time is 0.05–24 h. Preferably, the temperature is 45–85°C, and the reaction time is 0.3–4 h.

[0050] In the silk fibroin / lithium bromide blend solution, the mass fraction of silk fibroin is 1.0–10.0 wt%.

[0051] S2, add conductive material and crosslinking agent to the silk fibroin / lithium bromide blend solution obtained in step S1 to obtain a second mixed solution; then place the second mixed solution in an oven for incubation to obtain an antifreeze conductive dual-network hydrogel based on silk fibroin.

[0052] The amount of conductive material used is 0.5%-2% of the silk fibroin protein content in the silk fibroin / lithium bromide blend solution.

[0053] In the second mixed solution, the mass ratio of silk fibroin, conductive substance, and cross-linking agent is silk fibroin: conductive substance: cross-linking agent = 1:(0.5%-2%):(8.0-30%).

[0054] The conductive material is one or more of the following: carbon nanotubes, graphene oxide, Mxene, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate, polyimide, polyacetylene, polypyrrole, and polyaniline.

[0055] The crosslinking agent is selected from one or more of polyethylene glycol diglycidyl ether, horseradish peroxidase-H2O2, genipin, polyethylene glycol diglycidyl ether, carbodiimide, glutaraldehyde, 1,4-butanediol diglycidyl ether, tetraiodotetrachlorofluorescein, and riboflavin.

[0056] In this embodiment, degummed silk is dissolved in a lithium bromide solution, followed by the addition of a conductive material and thorough mixing. A cross-linking agent is then used to further cross-link the mixture, forming a silk fibroin conductive hydrogel. Under the action of the cross-linking agent, the silk fibroin and the conductive material can each form a cross-linked network. Furthermore, intermolecular forces exist between the silk fibroin and the conductive material, which helps anchor the conductive material within the gel matrix. The high concentration of ions and the conductive network in the gel, acting as a conductive medium, jointly promote the sensing sensitivity and stability of the conductive hydrogel. In addition, lithium bromide disrupts the hydrogen bonds between water molecules, and the formation of the dual network significantly lowers the freezing point of the gel system. The hydrogel prepared by this invention exhibits stable and non-destructive mechanical properties, conductive sensing performance, and ultrafast response / recovery time under ultra-low temperature conditions, making it suitable for ultra-low temperature environments, such as human motion monitoring in polar expeditions and flexible robotics.

[0057] This application also provides a silk fibroin-based antifreeze conductive dual-network hydrogel, which is prepared by the aforementioned technical solution. The silk fibroin-based antifreeze conductive dual-network hydrogel has a dual-network structure, and the chemical cross-linking agent forms covalent bonds with both the silk fibroin and the conductive material to form two cross-linking networks.

[0058] The antifreeze conductive dual-network hydrogel based on silk fibroin is used in fields such as human motion monitoring, climate monitoring, and flexible robots in extremely cold weather, such as polar expeditions.

[0059] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0060] Example 1

[0061] A method for preparing an antifreeze conductive dual-network hydrogel based on silk fibroin includes the following steps:

[0062] S1, 1.5g of degummed silk is mixed with 10mL of 9.3mol / L lithium bromide and heated to 60℃ to dissolve. The mixture is homogeneous to obtain a silk fibroin / lithium bromide blend solution.

[0063] S2, add conductive material PEDOT:PSS and crosslinking agent 1,4-butanediol diglycidyl ether to the silk fibroin / lithium bromide blend solution obtained in step S1 to obtain a second mixed solution; then inject the second mixed solution into a mold and incubate it in an oven to obtain an antifreeze conductive double network hydrogel based on silk fibroin.

[0064] The amount of conductive material added is 2% of the amount of silk fibroin in the silk fibroin / lithium bromide blend solution, and the amount of crosslinking agent added is 15% of the amount of silk fibroin in the silk fibroin / lithium bromide blend solution.

[0065] That is, in the second mixed solution, the mass ratio of silk fibroin, conductive substance, and cross-linking agent is silk fibroin: conductive substance: cross-linking agent = 1:2%:15%.

[0066] Examples 2-4 and Comparative Examples 1-2

[0067] Compared with Example 1, the main difference lies in the amount of conductive material used in step S2, that is, the mass ratio of silk fibroin, conductive material, and crosslinking agent in the second mixed solution is changed; other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here. Details are shown in the table below.

[0068]

[0069]

[0070] Please see Figure 1 The images shown are actual pictures of the hydrogels prepared in Examples 1-4 and Comparative Example 1.

[0071] Infrared spectroscopy was performed on the hydrogels prepared in Examples 1-4 and Comparative Example 1, and the results are as follows: Figure 2 As shown, the peak positions of the silk fibroin are at 1655, 1546, 1511, and 1243 cm⁻¹. -1 Its conformation is mainly characterized by random curls, 1605cm -1 This is a C-C stretching vibration mode within the benzene ring of the fluorene group, 836 cm⁻¹. -1 The peak at position 1 represents the stretching vibration peak of CS in PEDOT:PSS, which disappears in the blended gel, indicating the formation of a conductive material network.

[0072] Furthermore, the chemical structures of PEDOT:PSS before and after treatment with 1,4-butanediol diglycidyl ether (BDDE) were analyzed using XPS, and the results are as follows: Figure 3 As shown, the S2p nuclear level spectral lines changed significantly after the addition of BDDE. 1S The spectra show that after reacting with BDDE, the binding energy of the sulfonate in PSS increases, and the area of ​​CO (285.7 eV) relative to CC / C=C (283.8 eV) increases significantly, indicating that chemical cross-linking has been achieved between the free sulfonic acid in PSS and the epoxide of BDDE. That is, a stable network structure is formed between PEDOT and PSS.

[0073] The conductivity of the hydrogels prepared in Examples 1-4 and Comparative Example 1 was tested using a Hiokki IM3536 LCR, and the conductivity of the hydrogels was measured in the frequency range of 10 Hz to 10 MHz.

[0074] from Figure 4 As can be seen, the conductivity of the silk fibroin hydrogel without the addition of conductive materials is 9.46 S / m. -1 When the amount of conductive material added is 2%, the conductivity is significantly increased to 16.33 S m. -1 This indicates that the formation of a conductive material network significantly improves the conductivity of the hydrogel. However, when the conductive material content is further increased to 2.5%, significant aggregation occurs in the silk fibroin / lithium bromide solution, such as... Figure 5 As shown, the maximum loading of the conductive material is 2.0%.

[0075] Comparative Example 3

[0076] This comparative example provides a method for preparing a hydrogel. Compared with Example 1, the main difference is that the gel in Example 1 is desalted to remove lithium bromide. The remaining steps are basically the same as in Example 1 and will not be repeated here.

[0077] The hydrogels obtained in Comparative Example 3 and Example 1 were desalted and then their conductivity was tested. The results are as follows: Figure 6 As shown.

[0078] As can be seen, compared to the silk fibroin hydrogel without the addition of conductive materials, the conductivity of the desalted water gel only increased slightly by 0.3 Sm after adding 2.0% PEDOT:PSS. -1 Around 6.87 S m. In contrast, in the presence of LiBr (Example 1), the conductivity of the hydrogel increased significantly by 6.87 S m. -1 That is, the addition of 2.0% PEDOT:PSS significantly increased the conductivity by about 23 times.

[0079] As can be seen, the hydrogel prepared in this invention is mainly ionically conductive, and the addition of the PEDOT:PSS network can further significantly improve its conductivity. We speculate that this may be because the multiple conductive pathways constructed by the PEDOT:PSS network and LiBr significantly improve the conductivity of the SPL hydrogel.

[0080] The hydrogel prepared in Example 1 of this invention was connected to a wire, and then the hydrogel was applied to the elbow, wrist, fingers and knee respectively. After bending the elbow, wrist, fingers and knee, the hydrogel returned to its original state (parallel). This bending cycle was repeated multiple times, and the resistance change of the hydrogel during the stretching process of the elbow, wrist, fingers and knee was recorded in real time using an electrometer.

[0081] Calculate the rate of change of relative resistance using the following formula:

[0082] Relative resistance change rate (%) = ΔR / R0*100;

[0083] Where R0 is the initial resistance (Ω) of the hydrogel sample, and ΔR is the change in resistance (Ω) of the hydrogel during stretching at the elbow, wrist, finger, and knee.

[0084] Figure 7 This is a graph showing the relative resistance change rate when the hydrogel obtained in Example 1 of the present invention is applied to the elbow, wrist, fingers, and knee during bending cycles.

[0085] from Figure 7 As can be seen, after multiple bending cycles, the rate of change of its resistance remains relatively stable and highly repeatable. These results indicate that the hydrogel sensor has excellent stability and holds promise as a wearable strain sensor for detecting electrical signals from motion in different parts of the body.

[0086] Furthermore, to verify the low-temperature resistance of the conductive hydrogel obtained in Example 1, the freezing point of the sample was further measured using differential scanning calorimetry (DSC, TA Q2000, USA), and the results are as follows. Figure 8 As shown, the freezing point of the hydrogel is -108℃, indicating that the hydrogel can function effectively in a sub-zero temperature range not exceeding -108℃.

[0087] Furthermore, to test the environmental stability and durability of the flexible sensor, it was placed in environments at room temperature and -80°C, and its resistance change rate curve was measured after 1000 consecutive load-unload cycles under a strain of 20%. The results are as follows: Figure 9 As shown.

[0088] As can be seen, the resistance change rate curves at the initial, intermediate, and final stages of the test did not show significant changes, and the relative resistance change rate of the hydrogel flexible sensor against strain did not change much in environments at room temperature and -80℃, indicating that the flexible sensor has high environmental stability and excellent durability.

[0089] Examples 5-6 and Comparative Examples 4-5

[0090] Compared with Example 1, the main difference is that the amount of crosslinking agent used in step S2 has been changed; other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here. Details are shown in the table below.

[0091] The compressive strength and elastic recovery rate of the obtained hydrogel were tested, and the results are shown in the table below.

[0092]

[0093] As shown in the table above, when the crosslinking agent content is 8.0-30%, the compressive strength of the gel gradually increases with the increase of the crosslinking agent content; the highest elastic recovery rate is found when the crosslinking agent content is 15%. When the crosslinking agent content is 5.0% (Comparative Example 4), the crosslinking density of the gel is relatively low, and its mechanical properties and elastic recovery rate are significantly reduced compared to Example 1, making it unsuitable for use as a strain sensor. When the crosslinking agent content increases to 40% (Comparative Example 5), the crosslinking density of the gel increases significantly, resulting in a significantly higher compressive strength than that of the gel obtained in Example 1. However, the elastic recovery rate decreases significantly to only 85.6%, and the flexibility is greatly reduced. When used as a strain sensor, this is not conducive to the non-destructive detection of sensing signals. In addition, it cannot provide effective electrical signal feedback for small deformations.

[0094] It should be noted that the conductive material can also be one or more of the following conductive materials: carbon nanotubes, graphene oxide, Mxene, polyimide, polyacetylene, polypyrrole, polyaniline, etc.

[0095] The crosslinking agent can be one or more of polyethylene glycol diglycidyl ether, horseradish peroxidase-H2O2, genipin, polyethylene glycol diglycidyl ether, carbodiimide, glutaraldehyde, 1,4-butanediol diglycidyl ether, tetraiodotetrachlorofluorescein, and riboflavin.

[0096] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a silk fibroin-based antifreeze conductive dual-network hydrogel, characterized in that, Includes the following steps: S1, degummed silk is mixed with lithium bromide and heated to dissolve, yielding a silk fibroin / lithium bromide blend solution; the mass fraction of silk fibroin in the silk fibroin / lithium bromide blend solution is 1.0~10.0 wt%; S2, add a conductive substance and a crosslinking agent to the silk fibroin / lithium bromide blend solution obtained in step S1 to obtain a second mixed solution; then place the second mixed solution in an oven for incubation, and the silk fibroin and the conductive substance form crosslinked networks under the action of the crosslinking agent to obtain an antifreeze conductive dual-network hydrogel based on silk fibroin; the conductive substance is poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate; In the second mixed solution, the mass ratio of silk fibroin, conductive substance, and cross-linking agent is silk fibroin: conductive substance: cross-linking agent = 1: (0.5%-2%): (8.0%-30%).

2. The method for preparing the antifreeze conductive dual-network hydrogel based on silk fibroin according to claim 1, characterized in that, The concentration of lithium bromide is 7.0-11.0 mol / L.

3. The method for preparing the antifreeze conductive dual-network hydrogel based on silk fibroin according to claim 1, characterized in that, In step S1, the temperature for the heating and dissolution treatment is 30~120 ℃, and the reaction time is 0.05~24 h.

4. The method for preparing the antifreeze conductive dual-network hydrogel based on silk fibroin according to claim 1, characterized in that, The crosslinking agent is selected from one or more of polyethylene glycol diglycidyl ether, horseradish peroxidase-H2O2, genipin, polyethylene glycol diglycidyl ether, carbodiimide, glutaraldehyde, 1,4-butanediol diglycidyl ether, tetraiodotetrachlorofluorescein, and riboflavin.

5. A silk fibroin-based antifreeze conductive dual-network hydrogel, characterized in that, The antifreeze conductive dual-network hydrogel based on silk fibroin, prepared by any one of claims 1-4, has a conductive material cross-linking network and a silk fibroin cross-linking network.

6. The application of the antifreeze conductive dual-network hydrogel based on silk fibroin as described in claim 5, characterized in that, The antifreeze conductive dual-network hydrogel based on silk fibroin is used for human motion monitoring in polar expeditions and in the field of flexible robotics.

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