CN114854052A

CN114854052A - Self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel and preparation method and application thereof

Info

Publication number: CN114854052A
Application number: CN202210788445.5A
Authority: CN
Inventors: 郑海艳; 张锋; 左保齐
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2022-07-06
Filing date: 2022-07-06
Publication date: 2022-08-05

Abstract

The invention provides a self-repairing self-adhesive silk fibroin anti-freezing conductive hydrogel as well as a preparation method and application thereof.

Description

Self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel and preparation method and application thereof

Technical Field

The invention relates to the field of flexible biological strain sensors, in particular to a self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel and a preparation method and application thereof.

Background

Hydrogels are water-rich, soft, wet materials formed by the cross-linking of three-dimensional polymer networks. Due to the advantages of various structures, forms and multifunctionality, the material is widely applied to the fields of tissue engineering, biomedicine, flexible electronics and the like. However, most of the raw materials of the current hydrogel are synthetic polymer macromolecules, which face the problems of limited raw material sources, environmental pollution and biocompatibility in application. Based on sustainable and green development and the requirement on biocompatibility in most applications, renewable natural polymer biomass materials are developed and converted into hydrogel materials with higher additional value, which accords with the development trend and sustainable development view of ecological friendly material utilization in China.

The silk is rich natural biomass high-molecular protein, is safe and non-toxic, has no immunogenicity, and has excellent biocompatibility. As one of the high-quality and important basic raw materials in the textile industry, the history of more than 4000 years is available. In recent decades, silk has been processed into various forms by dissolution regeneration (regenerated silk fibroin-SF) with the deep understanding of the chemical properties and structure of silk. Besides the aspects of biological medical and tissue engineering, SF is an ideal choice for designing electronic components. The design of the functional SF hydrogel and the application of the functional SF hydrogel in the flexible strain sensor break the limitation of silk application, not only exert the advantage of SF, but also widen the application field of silk by intelligent and high-value utilization.

However, hydrogels have a high water content, with a large amount of free water. The ordered aggregation of free water and the phase transition of water in the low-temperature environment make the hydrogel easy to freeze and crystallize, and then the hydrogel becomes brittle and hard, loses the original stretchability, skin compliance and other functions. The flexible strain sensor is inevitably used in a low-temperature environment, so that the above problems greatly limit the use environment. In addition, the long-time exposure of the hydrogel at room temperature may cause the evaporation of free water, so that the structure of the hydrogel flexible sensor is changed, the use stability is further lost, and the service life is shortened. Therefore, the design of a hydrogel flexible strain sensing material with freezing resistance and moisture retention property is gradually receiving attention of scholars.

In this regard, the introduction of or treatment with polyols (ethylene glycol-EG, glycerol, sorbitol, etc.) is a simple, intuitive and effective method. Polyols are the simplest orthoalcohols and are low in volatility and hygroscopicity and are often used as effective inhibitors of water freezing. Mixing with water to obtain binary solution, and adjusting the ratio of polyhydric alcohol to water to lower the freezing point to below-45 deg.C, which is far lower than that of pure polyhydric alcohol and water. For example, Wen J et al combine tannic acid coated hydroxyapatite nanowires, polyvinyl alcohol, polyols, and metal ions to make a conductive hydrogel that still exhibits strain sensitivity at-30 ℃ and is useful as a sensor for detecting strain, pressure, and temperature. Chen F, et al, placed a tough organic hydrogel formed by crosslinking alginate/polyacrylamide in a solution of polyol, glycerol, sorbitol, or a mixture of the three, and displaced the water molecules in the hydrogel with the above solution, and the resulting hydrogel was also mechanically flexible at-70 deg.C. Su X et al used polyacrylic acid, polyvinyl alcohol, sodium tetraborate and polyol/H ₂ The binary O solvent develops an extreme temperature resistant anti-freezing moisture-keeping conductive hydrogel which can keep stable conductivity even at the temperature of minus 60 ℃.

However, low temperatures may cause crystallization within the polymer chains, reducing or limiting the mobility of the polymer chains within the hydrogel, impairing its ion transport capacity. Therefore, except for basic stretchability, electrical performance and strain sensing performance, most of the hydrogel flexible strain sensors with freeze resistance and moisture retention performance do not have adhesiveness, and need to be additionally adhered to a human body by means of an adhesive tape and the like for performing behavior monitoring, or lack of rapid self-repairing capability and biological safety, which is not favorable for the fidelity, the use stability and the service life of signal monitoring. Therefore, the design of the anti-freezing hydrogel which still keeps the functions of self-repairing, self-adhesion and the like in a low-temperature environment is very important and needs to be solved urgently.

Disclosure of Invention

The technical problem to be solved is as follows: the invention aims to provide a high-moisture-retention fibroin conductive hydrogel which can still maintain a wide working strain range at low temperature, has skin compliance, rapid self-repairing and excellent self-adhesion capability, has stable electrical properties and dynamic durability.

The technical scheme is as follows: a preparation method of a self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel comprises the following steps:

s1 preparation of silk fibroin solution: degumming, dissolving and dialyzing raw silk to obtain a purified silk fibroin aqueous solution, and concentrating the silk fibroin aqueous solution to a certain concentration to obtain a silk fibroin solution;

s2 preparation of polyol/polyvinyl alcohol mixed solution: adding polyvinyl alcohol into a polyol aqueous solution, and uniformly mixing to obtain a polyol/polyvinyl alcohol mixed solution;

s3 preparation of the fibroin/polyalcohol/polyvinyl alcohol mixed solution: adding the silk fibroin solution prepared in the step S1 into the mixed solution of the polyol and the polyvinyl alcohol prepared in the step S2, and uniformly mixing to obtain a mixed solution of the silk fibroin, the polyol and the polyvinyl alcohol;

s4 preparation of borax/polyalcohol/tannic acid mixed solution: adding borax into a polyol aqueous solution to obtain a borax solution, then adding tannic acid into the borax solution, and uniformly mixing to obtain a borax/polyol/tannic acid mixed solution;

s5, preparation of self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel: and (4) adding the borax/polyol/tannin mixed solution prepared in the step S4 into the fibroin/polyol/polyvinyl alcohol mixed solution prepared in the step S3, mixing and crosslinking, and performing freeze-thawing treatment to obtain the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel.

Preferably, the polyhydric alcohol is one or a combination of two or more of ethylene glycol, glycerol and sorbitol.

Preferably, the preparation method of the silk fibroin solution in the step S1 is: adding raw silk into 0.05wt% of Na ₂ CO ₃ Degumming in the solution to remove sericin on the surface of the raw silk, and drying the degummed raw silk to obtain fibroin; dissolving fibroin in 9.3mol/L LiBr solution, and permeating with deionized water at room temperatureAnd (4) separating to obtain a silk fibroin aqueous solution, and filtering and concentrating the silk fibroin aqueous solution to obtain the silk fibroin solution.

Preferably, the concentration of the fibroin solution in the step S1 is 8-15 wt%.

Preferably, the process of the freeze-thaw treatment in the step S5 is as follows: freezing for 6-20 h at the temperature of-30 to-20 ℃, and then unfreezing at room temperature. A self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel prepared by the preparation method.

Preferably, the mass ratio of polyvinyl alcohol, fibroin, borax, tannic acid, polyol and water in the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is 3-5: 1-4: 0.4-1: 0.5-2.5: 40-50: 40 to 50.

Preferably, the mass ratio of polyvinyl alcohol, fibroin, borax, tannic acid, polyol and water in the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is 4: 3: 0.6: 1.25: 45.575: 45.575.

the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is applied to preparation of a flexible strain sensor, and the flexible strain sensor comprises health detection (various physiological signals), motion monitoring and rehabilitation monitoring.

Has the advantages that: the hydrogel prepared by the invention has the following advantages:

1. the invention combines a freezing and thawing treatment to balance internal functions by introducing a freezing and moisturizing functional mechanism (polyhydric alcohol/water binary solvent), combines polyvinyl alcohol, borax, fibroin and tannic acid to prepare the self-repairing, self-adhesive, freezing and moisturizing fibroin conductive hydrogel, and can be used as a flexible strain sensor and applied to a low-temperature environment;

2. the mussel-simulated adhesion mechanism of the tannic acid and a hydrogen bond donor provided by a large number of hydroxyl groups in the hydrogel enable the hydrogel to show excellent adhesion capability to different substrates; and the adhesion capability is enhanced along with the improvement of the cohesive force (mechanical property) of the hydrogel caused by the effects of the polyhydric alcohol and the freeze-thaw; the multiple dynamic reversible bonds form a complete network in the gel, and simultaneously endow the hydrogel with the self-repairing capability of high repairing efficiency in the aspects of mechanical property, electrical property and strain sensing property without external stimulation. The polyhydric alcohol and the tannin have good inhibition on escherichia coli and staphylococcus aureus in a synergistic manner;

3. on one hand, the hydrogen bond effect of the polyhydric alcohol, water, polyvinyl alcohol and SF effectively prevents water molecules from orderly aggregating at low temperature to form ice crystals, endows the hydrogel with frost resistance, and can be enhanced along with the increase of the content of the polyhydric alcohol; on the other hand, the vapor pressure of water is reduced, free water in the hydrogel is locked in a gel network, water molecules are effectively prevented from evaporating, the hydrogel is endowed with high moisture retention, and the frost resistance and the water retention capacity are enhanced along with the increase of the content of the polyhydric alcohol;

4. complete gel network, B (OH) ^4- And Na ⁺ The existence and excellent self-repairing capability of the hydrogel enable the hydrogel to have a wide working strain range (>200%), ability to distinguish magnitude strain, distinguish movement direction, stable electrical performance and dynamic durability. The hydrogel is directly adhered to the surface of the skin, and can realize the monitoring of the movement behaviors of large strain and small strain, such as joint movement, micro expression change, physiological signal change and the like;

5. the freeze-thaw treatment makes up the loss of mechanical properties caused by reducing the content of polyvinyl alcohol for balancing the stretchability and the self-repairing property after a large number of hydrogen bonds are introduced into the gel network, so that the hydrogel can simultaneously keep the stretchability, the skin compliance, the self-repairing property and the self-adhesion property. The excellent low temperature resistance and the functional factor enable the hydrogel to still maintain the functions at low temperature. Therefore, the hydrogel can dynamically monitor the body movement in a highly sensitive, fast-responding and stable state at a low temperature (-23 ℃), and silent communication can be realized by expressing Morse code through regular movement based on the stability of electrical properties.

6. The conductive hydrogel used in the low-temperature environment has the low-temperature self-repairing and self-adhering capabilities, and provides a new idea for the design of a low-temperature flexible strain sensor.

Drawings

FIG. 1 is a self-repairing mechanism of a self-repairing, self-adhesive silk fibroin antifreeze conductive hydrogel (hereinafter referred to as PSEBT);

FIG. 2 shows the influence of different components and processes on the anti-freezing property of the PSEBT hydrogel, (a) macroscopic picture of the hydrogel of each component frozen at-25 ℃, (b) flexibility of PS and PSEBT at low temperature, and (c) DSC curve of the hydrogel of each component;

fig. 3 is a water retention of the PSEBT hydrogel, (a) macroscopic picture, (b) mass retention;

fig. 4 is a tensile stress-strain curve of the PSEBT hydrogel;

FIG. 5 is a graph of the electrical and strain sensing self-repairability of PSEBT-1/1 hydrogel, (a) resistance recovery before and after repeated breaks, (b) break-make-and-break strain sensing repair;

FIG. 6 is a mechanical property self-repairability of PSEBT-1/1 hydrogel, (a) continuous step test of PSEBT under different strains, and (b) tensile stress-strain curve of mechanical property self-repair;

FIG. 7 shows the adhesion of PSEBT-1/1 hydrogel (a) macroscopic picture (room temperature), (b) adhesion mechanism;

FIG. 8 shows the electrical properties and strain sensitivity of the PSEBT-1/1 hydrogel, (a) electrical conductivity, (b) a strain sensitivity test object, (c) dependence of PSEBT resistance on strain, and (d) sensitivity coefficient;

FIG. 9 shows the electrical property stability and dynamic durability of PSEBT-1/1 hydrogel, (a) resistance change under different strains, (b) resistance change for consecutive multiple tensile cycles under the same strain;

FIG. 10 is a graph of the low temperature resistance of PSEBT-1/1 hydrogel, (a) low temperature self-healing, (b) low temperature adhesion, (c) low temperature strain sensitivity and electrical self-healing;

FIG. 11 shows PSEBT-1/1 as a flexible strain sensor attached to each joint of a human body to monitor human body motion in real time, (a) finger joints, (b) wrist joints, (c) elbow joints, and (d) knee joints;

FIG. 12 shows a PSEBT-1/1 flexible strain sensor for human motion monitoring at low temperature;

FIG. 13 is a representation of a PSEBT-1/1 flexible strain sensor in communication at low temperature by Morse code.

Detailed Description

The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.

Example 1

A preparation method of a self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel comprises the following steps:

s1 preparation of silk fibroin solution: 150g of raw silk was placed in 6L of Na having a concentration of 0.05wt% ₂ CO ₃ Boiling the solution at 100 deg.C for 30min, and washing silkworm raw silk with 60 deg.C deionized water. Repeating the process for three times to remove sericin on the surface of the raw silk, and then drying in a 60 ℃ oven for 12 hours to obtain fibroin; slowly adding 10g of degummed fibroin into 9.3mol/L LiBr solution with the volume of 40ml for several times, dissolving for 4 hours at 60 ℃, putting into a dialysis bag, dialyzing for 72 hours with deionized water at normal temperature, and replacing the deionized water every 4 hours; after the dialysis bag is taken out, filtering the obtained SF aqueous solution by using a cotton wool ball, then opening the filter, and concentrating in a forced air drying box at 60 ℃ until the solid content in the silk fibroin solution is 10 wt%;

s2 preparation of ethylene glycol/polyvinyl alcohol mixed solution: adding polyvinyl alcohol into an ethylene glycol aqueous solution, and heating and dissolving for 3 hours at the temperature of 98 ℃ to obtain an ethylene glycol/polyvinyl alcohol mixed solution;

s3 preparation of the fibroin/ethylene glycol/polyvinyl alcohol mixed solution: adding the silk fibroin solution prepared in the step S1 into the ethylene glycol/polyvinyl alcohol mixed solution prepared in the step S2, and uniformly mixing at normal temperature to obtain a silk fibroin/ethylene glycol/polyvinyl alcohol mixed solution;

s4 preparation of borax/glycol/tannic acid mixed solution: adding borax into an ethylene glycol aqueous solution to obtain a borax solution, then adding tannic acid into the borax solution, and uniformly mixing to obtain a borax/ethylene glycol/tannic acid mixed solution;

s5, preparation of self-repairing and self-adhesive silk fibroin antifreeze conductive hydrogel: adding the borax/glycol/tannin mixed solution prepared in the step S4 into the fibroin/glycol/polyvinyl alcohol mixed solution prepared in the step S3, mixing and crosslinking, freezing and thawing at-25 ℃ for 8 hours, and thawing at room temperature to obtain the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel;

the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is characterized in that the mass ratio of polyvinyl alcohol, fibroin, borax, tannic acid, ethylene glycol and water in the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is 4: 3: 0.6: 1.25: 45.575: 45.575, the hydrogel obtained by the above preparation process was named PSEBT-1/1.

Example 2

s1 preparation of silk fibroin solution: 150g of raw silk was placed in 6L of Na having a concentration of 0.05wt% ₂ CO ₃ Boiling the solution at 100 deg.C for 30min, and washing silkworm raw silk with 60 deg.C deionized water. Repeating the process for three times to remove sericin on the surface of the raw silk, and then drying in a 60 ℃ oven for 12 hours to obtain fibroin; slowly adding 10g of degummed fibroin into 9.3mol/L LiBr solution with the volume of 40ml for several times, dissolving for 4 hours at 60 ℃, putting into a dialysis bag, dialyzing for 72 hours with deionized water at normal temperature, and replacing the deionized water every 4 hours; after the dialysis bag is taken out, filtering the obtained SF aqueous solution by using absorbent cotton balls, then, opening the filter to a blast drying box at 60 ℃ for concentration until the solid content in the silk fibroin solution is 10 wt%;

s5, preparation of self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel: adding the borax/glycol/tannin mixed solution prepared in the step S4 into the fibroin/glycol/polyvinyl alcohol mixed solution prepared in the step S3, mixing and crosslinking, freezing and thawing at-25 ℃ for 8 hours, and thawing at room temperature to obtain the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel;

the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is characterized in that the mass ratio of polyvinyl alcohol, fibroin, borax, tannic acid, ethylene glycol and water in the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is 4: 3: 0.6: 1.25: 18.23: 72.92 the hydrogel prepared by the above preparation process was named PSEBT-1/4.

Example 3

the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is characterized in that the mass ratio of polyvinyl alcohol, fibroin, borax, tannic acid, ethylene glycol and water in the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is 4: 3: 0.6: 1.25: 36.46: 54.69, the hydrogel obtained by the above preparation process was named PSEBT-2/3.

Example 4

the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is characterized in that the mass ratio of polyvinyl alcohol, fibroin, borax, tannic acid, ethylene glycol and water in the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is 4: 3: 0.6: 1.25: 54.69: 36.46, the hydrogel obtained by the above preparation process was named PSEBT-3/2.

Comparative example 1

s5, preparation of self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel: adding the borax/ethylene glycol/tannic acid mixed solution prepared in the step S4 into the fibroin/ethylene glycol/polyvinyl alcohol mixed solution prepared in the step S3, and mixing until crosslinking to obtain the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel;

the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is characterized in that the mass ratio of polyvinyl alcohol, fibroin, borax, tannic acid, ethylene glycol and water in the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is 4: 3: 0.6: 1.25: 45.575: 45.575, the hydrogel obtained by the above preparation process was named N-PSEBT.

Comparative example 2

The hydrogel is prepared from polyvinyl alcohol, fibroin and water, wherein the mass of the polyvinyl alcohol, the fibroin and the water is 4: 3: 45.575, the hydrogel is named PS.

Comparative example 3

The hydrogel is prepared from polyvinyl alcohol, fibroin, ethylene glycol and water, wherein the mass of the polyvinyl alcohol, the fibroin, the ethylene glycol and the water is 4: 3: 45.575: 45.575 the hydrogel was named PSE.

The performance of the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel prepared in the above examples and comparative examples was tested.

The self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel prepared in the embodiment 1 is used as a conductor to be connected into a circuit, and it can be seen from fig. 1 that when the cross section of the hydrogel is damaged by the outside and is contacted again, the quick reconstruction capability of the hydrogel network is reconnected with the conductive path in the hydrogel, so that the hydrogel has the electrical self-repairing capability.

The hydrogels prepared in examples 1 to 4 and comparative examples 1 to 3 were observed for freezing resistance, water retention and mechanical property test, and the results are shown in fig. 2 and 3. As can be seen from the figures 2 and 3, the hydrogen bonding of the ethylene glycol with water, the polyvinyl alcohol and the fibroin effectively prevents water molecules from orderly aggregating at low temperature to form ice crystals on one hand, endows the hydrogel with the freezing resistance (PSEBT-1/1, the phase transition temperature is as low as-39 ℃), and can be enhanced along with the increase of EG content; on the other hand, the vapor pressure of water is reduced, free water in the hydrogel is locked in a gel network, water molecules are effectively prevented from evaporating, PSEBT is endowed with high moisture retention (the mass retention rate of PSEBT-3/2 for 24h is 97 percent at 25 ℃, and 77 percent after 14 days), and the frost resistance and the water retention capacity are enhanced along with the increase of EG content; as shown in fig. 4, the fracture stress of the four groups of PSEBT after freeze-thaw treatment (examples 1 to 4) is significantly better than that of the N-PSEBT without freeze-thaw treatment (comparative example 1), which indicates that the freeze-thaw treatment forms secondary crosslinking inside the gel, which has a significant effect on improving the mechanical properties of the PSEBT hydrogel. A microcrystalline region is formed among hydroxyl groups of a PVA molecular chain in the freezing and thawing process, so that the mechanical property is enhanced.

The PSEBT-1/1 prepared in example 1 was subjected to the cut-and-self-repair continuously for a plurality of times, and as can be seen from fig. 5 (a), the resistance of the PSEBT-1/1 hydrogel rapidly increased to infinity at the moment of cut (actually monitored as air resistance at this time), and rapidly returned to the initial value at the moment of re-contact. After going through the successive repeated switching-off process, the resistance of PSEBT-1/1 can still be quickly restored to the initial value within 6 s. Based on the flexible mechanical properties of PSEBT-1/1, the hydrogel was adhered to the finger, the hydrogel was cut off during repeated finger bending, and the finger was again bent and then the finger was again bent, and the results in FIG. 5 (b) show that the resistance of the hydrogel could still be quickly restored to its original state within a few seconds. The PSEBT-1/1 has excellent self-repairing capability of electrical properties, not only has strain sensing, but also has self-repairing capability of strain sensing; FIG. 6 (a) shows the continuous strain step test curve of PSEBT-1/1, which shows that the gel internal network is reconstructed in a short time, the service life of PSEBT-1/1 is excellent in self-repairing property of mechanical properties, and the self-repairing efficiency of PSEBT-1/1 is as high as 94.31% (FIG. 6 (b)).

FIG. 7 is a macroscopic picture of the bonding of PSEBT-1/1 to different substrate surfaces, as shown in FIG. 7 (a), PSEBT-1/1 has excellent bonding performance. Can easily adhere to different surfaces such as PTFE, plastic, wood, iron, glass, human skin and the like, and the adhesion mechanism is shown in figure 7 (b).

The PSEBT-1/1 prepared in example 1 was subjected to electrical property test, and it can be seen from FIGS. 8 and 9 that the hydrogel formed an intact gel network, B (OH) ^4- And Na ⁺ The existence and excellent self-repairing capability of the PSEBT lead the PSEBT to have a wide working strain range (>200%), ability to distinguish magnitude strain, distinguish movement direction, stable electrical performance and dynamic durability.

In addition to the loss of flexibility and stretchability of the hydrogel caused by the freezing crystallization of water molecules at low temperature, the conductivity of the hydrogel is lost by limiting the movement of ions/electrons in the gel network, or the self-repairability is affected by interfering with the reconstruction of dynamic covalent/non-covalent bonds due to the restriction of the movement of molecular chains at low temperature. The elimination or reduction of hydrogel properties caused by the low temperature environment greatly limits the range of hydrogel applications. FIG. 10 further characterizes the self-repairability, viscosity, conductivity, etc. of the PSEBT-1/1 hydrogel at low temperature, and it can be observed from FIG. 10 that the PSEBT-1/1 gel can still realize self-repair quickly when the two hydrogels are contacted again at-20 ℃ after being kept at-20 ℃ for 24h, and after being repaired for 10min, the hydrogel is still not broken even if being stretched from a circular shape into a long strip shape, which indicates that the PSEBT-1/1 hydrogel has good quick self-repairability with low-temperature mechanical properties; after the hydrogel is separated into two pieces and the circuit is opened, the light emitting diode is lighted again. The above phenomena show that the PSEBT-1/1 has the advantages of low-temperature mechanical property stability, low-temperature adhesiveness and low-temperature self-repairability, the good environmental stability of the hydrogel ensures that the movement of conductive ions in a gel network is not influenced at the temperature of-20 ℃, the PSEBT-1/1 has excellent low-temperature resistance, and the conductivity and the strain sensitivity are still realized in the low-temperature environment.

The PSEBT-1/1 prepared in example 1 is used as a flexible strain sensor to be adhered to each joint of a human body to monitor the motion of the human body in real time, and as can be seen from fig. 11, the PSEBT-1/1 can realize large strain motion monitoring of each joint, and can sense the change of motion speed and distinguish the motion direction.

Most of the ionic hydrogel type strain sensors cannot adapt to the low-temperature environment because the hydrogel is frozen and crystallized in the low-temperature environment, so that the hydrogel performance is unstable or the original performance is lost. As shown in fig. 12, the flexible strain sensor PSEBT-1/1 can continuously monitor the bending movement of the finger joint without any obstacle even at low temperature, and changes the mechanical signal generated in each bending-straightening process into stable and clear electrical signal changes, and outputs and records the stable and clear electrical signal changes. The rate of change of resistance of the hydrogel remained stable after successive and at least more than 160 bending behaviors. The difference between the waveforms is due to the difficulty in maintaining a perfect agreement in each bending action. FIG. 13 shows that PSEBT-1/1 can continuously emit "COME HERE", "SOS", "HELP" signals in low temperature environment through the realization of Morse code information expression.

In conclusion, the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel provides a new way for developing a flexible strain sensor which is suitable for being used in a low-temperature environment and has good biological safety.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A preparation method of a self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel is characterized by comprising the following steps:

2. The preparation method of the self-repairing, self-adhesive silk fibroin anti-freezing conductive hydrogel according to claim 1, which is characterized in that: the polyalcohol is one or a combination of two or more of ethylene glycol, glycerol and sorbitol.

3. The method for preparing the self-repairing, self-adhesive silk fibroin anti-freezing conductive hydrogel according to claim 1, wherein the method for preparing the silk fibroin solution in the step S1 comprises the following steps: adding raw silk into 0.05wt% of Na ₂ CO ₃ Degumming in the solution to remove sericin on the surface of the raw silk, and drying the degummed raw silk to obtain fibroin; dissolving fibroin in 9.3mol/L LiBr solution, and adding deionized water at normal temperatureAnd (4) dialyzing to obtain a silk fibroin aqueous solution, and filtering and concentrating the silk fibroin aqueous solution to obtain the silk fibroin solution.

4. The preparation method of the self-repairing, self-adhesive silk fibroin anti-freezing conductive hydrogel according to claim 1, which is characterized in that: the concentration of the fibroin solution in the step S1 is 8-15 wt%.

5. The preparation method of the self-repairing, self-adhesive silk fibroin anti-freezing conductive hydrogel according to claim 1, wherein the freeze-thaw treatment process in the step S5 is as follows: freezing for 6-20 h at the temperature of-30 to-20 ℃, and then unfreezing at room temperature.

6. A self-repairing, self-adhesive fibroin antifreeze conductive hydrogel prepared by the preparation method of any one of claims 1-5.

7. The self-repairing, self-adhering silk fibroin anti-freeze conductive hydrogel of claim 6, wherein: polyvinyl alcohol, fibroin, borax, tannic acid, polyol and water in the self-repairing and self-adhering silk fibroin antifreeze conductive hydrogel are in a mass ratio of 3-5: 1-4: 0.4-1: 0.5-2.5: 40-50: 40 to 50.

8. The self-repairing, self-adhering silk fibroin antifreeze conductive hydrogel of claim 7, wherein: in the self-repairing and self-adhesive silk fibroin anti-freezing conductive hydrogel, the mass ratio of polyvinyl alcohol, fibroin, borax, tannic acid, polyol to water is 4: 3: 0.6: 1.25: 45.575: 45.575.

9. the use of the self-healing, self-adhering silk fibroin antifreeze conductive hydrogel of claim 6 in the preparation of a flexible strain sensor.