Sericin low-hysteresis composite conductive hydrogel as well as preparation method and application thereof

Abstract

The invention discloses a sericin low-hysteresis composite conductive hydrogel as well as a preparation method and application thereof, the hydrogel takes a copolymer of methacrylamide phenylboronic acid and acrylamide as a matrix, and the composite conductive hydrogel is formed by introducing polydopamine modified sericin and aluminum ions. In the hydrogel, a boric acid group on a main chain reacts with a phenolic hydroxyl group into which sericin is introduced, so that the hydrogel has excellent self-repairing capability, and a secondary structure of the sericin is changed from disorder to alpha-helix and beta-folding in the reaction, so that the hydrogel has excellent low hysteresis capability; the introduction of aluminum ions provides good conductivity for the hydrogel. A sensor prepared from the hydrogel can respond to the deformation of human body movement and monitor the resistance change during joint movement, so that the real-time monitoring of the movement state is realized. The preparation process is simple and convenient, the materials are green and environment-friendly, and the method has wide application prospects and is suitable for the fields of design of wearable sensors, sports motion correction and the like.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials and flexible sensing technology, and particularly relates to a sericin low-hysteresis composite conductive hydrogel and a preparation method and application thereof. Background Art

[0002] Flexible conductive materials, due to their unique deformability and electrical conductivity, have shown great potential for application in flexible electronics, wearable devices, biomedical sensing and implants, soft robotics, and other fields. Conductive hydrogels, with their three-dimensional porous hydrophilic structure composed of a polymer network, combine excellent biocompatibility, skin affinity, environmental friendliness, and tunable electrical conductivity, making them an ideal candidate for meeting the needs of next-generation flexible wearable devices.

[0003] The preparation strategy of traditional multifunctional conductive hydrogels relies heavily on non-covalent interactions between polymer chains or between polymers and nanofillers (such as hydrogen bonds, ionic bonds, coordination bonds, hydrophobic interactions, van der Waals forces, π-π stacking, etc.). These forces are often used to give hydrogels self-repairing and stimulus-responsive properties due to their dynamic reversible properties. For example, CN115920791A discloses a method for preparing inorganic hydrogels based on nickel polyphosphate. The formation of the hydrogel mainly depends on nickel ions (Ni 2+ ) and phosphate ions (PO4 3- ) and the dynamic cross-linking network that successfully endows the hydrogel with super-stretching properties and self-healing capabilities. CN116808310A describes the preparation of a sandwich-structured hydrogel cartilage replacement material. This material significantly enhances the compressive strength of the hydrogel through the clever design of the synergistic cross-linking of multiple non-covalent bonds (such as hydrogen bonds and ionic bonds), enabling it to perform well in load-bearing applications (such as cartilage replacement).

[0004] However, the inherent low bond energy characteristics of non-covalent interactions have become a key bottleneck limiting the practical application of such hydrogels. Under external environmental stimuli (such as continuous mechanical stress, temperature changes, pH fluctuations, changes in ionic strength, etc.), non-covalent cross-linking points are prone to breakage and reorganization, resulting in uncontrollable dynamic changes in the hydrogel network structure. This is directly manifested in insufficient long-term stability of the material (such as unstable swelling / deswelling behavior, conductivity drift), easy attenuation of mechanical properties (such as strength, modulus, toughness), and significant energy dissipation under cyclic loads (i.e., high hysteresis). These defects seriously affect the reliability and service life of hydrogel devices in complex service environments.

[0005] In order to overcome the limitations of non-covalent cross-linking, research on the use of dynamic covalent chemistry to construct hydrogel networks has become increasingly active in recent years. Dynamic covalent bonds (DCBs) have the dynamic characteristics of reversible breakage and recombination under specific stimuli (such as heat, light, pH, and specific chemicals) while maintaining the high bond energy and stability of covalent bonds. This provides a new idea for designing hydrogels with both excellent stability and intelligent responsiveness (especially self-healing). The dynamic covalent bonds currently widely introduced into hydrogel systems include but are not limited to: disulfide bonds (-SS-), Schiff base bonds (-C=N-), borate bonds (BO), and Diels-Alder bonds. Through dynamic covalent cross-linking, the structural integrity and mechanical stability of hydrogels have been significantly improved, while retaining valuable self-healing capabilities.

[0006] Despite this, hydrogel materials will inevitably be subjected to repeated dynamic mechanical loads such as bending, stretching, and twisting in practical application scenarios such as flexible wearable devices. Many current hydrogels, including some dynamic covalent cross-linking systems, will experience significant energy dissipation due to friction, segment slippage, and reversible bond breakage / recombination within their networks when undergoing cyclic deformation, which manifests as high hysteresis. High hysteresis not only means low energy utilization efficiency, but more importantly, it will cause the hydrogel to be unable to fully recover to its original shape and size after unloading (i.e., there is permanent deformation or residual strain), and cause its electrical properties (such as resistance) to fluctuate unstably during the cycle. This instability will directly affect the signal accuracy, response consistency and long-term working reliability of devices such as hydrogel-based sensors, actuators or circuits, seriously restricting their practical application value.

[0007] Therefore, developing new high-performance conductive hydrogels that significantly improve their structural stability and mechanical durability while maintaining their necessary flexibility, conductivity, self-healing properties, and biocompatibility, and effectively reduce their hysteresis under cyclic loading, are key scientific issues and technical challenges that need to be addressed in this field. This is crucial for promoting the widespread application and industrialization of conductive hydrogels in high-end fields such as flexible wearable health monitoring, human-computer interaction interfaces, and implantable medical devices. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention provides a low-hysteresis sericin composite conductive hydrogel, its preparation method, and applications. Through a multi-level network design guided by dynamic borate bonds, this design simultaneously overcomes the three major challenges of traditional hydrogels: poor stability, high hysteresis, and low repair efficiency. By combining the natural advantages of sericin, this design achieves the unification of high-performance sensing, environmental friendliness, and wearability, providing key technical support for the large-scale application of flexible wearable devices in fields such as health monitoring and sports rehabilitation.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for preparing a sericin low-hysteresis composite conductive hydrogel comprises the following steps:

[0011] Step 1) dissolving a catalyst in deionized water to form an aqueous solution, adding dopamine and continuously stirring to allow dopamine to self-polymerize, then adding sericin and stirring to obtain a polydopamine-sericin solution;

[0012] Step 2) freeze-drying the polydopamine-sericin solution prepared in step 1) to obtain a powder, which is then mixed with an aluminum chloride solution to react and obtain a polydopamine-sericin-aluminum ion complex;

[0013] Step 3) adding methacrylamidophenylboronic acid and acrylamide to deionized water, then adding a crosslinking agent and an initiator, reacting to obtain a mixed solution, and then mixing the mixed solution with the polydopamine-sericin-aluminum ion complex prepared in step 2) to react, thereby obtaining the product.

[0014] Preferably, the catalyst in step 1) is one or more of hydrogen peroxide, ammonia water, triethylamine, sodium hydroxide, tetramethylethylenediamine, sodium carbonate, potassium hydroxide, acetic acid, and citric acid.

[0015] Preferably, the cross-linking agent in step 3) is one or more of N,N'-methylenebisacrylamide, glutaraldehyde, N,N'-diethylbisacrylamide, acryloyloxyethyltrimethoxysilane, ethylenediamine, propylene oxide, and aluminum chloride.

[0016] Preferably, the initiator in step 3) is one or more of azobisisobutyronitrile, dibenzoyl peroxide, ammonium persulfate, sodium persulfate, methylbenzothiazolone, Irgacure 651, and benzophenone.

[0017] Preferably, the specific steps of step 1) are as follows: first, 0.01-10 parts by weight of a catalyst is dissolved in 1-30 parts by weight of deionized water to form an aqueous solution, then 0.01-10 parts by weight of dopamine is added and continuously stirred to achieve dopamine self-polymerization, and then 0.01-10 parts by weight of sericin is added and continuously stirred at 500-2000 rpm at 20-80° C. for 0.5-20 hours.

[0018] Preferably, the specific steps of step 2) are as follows: freeze-drying the polydopamine-sericin solution prepared in step 1) for 24 to 48 hours to obtain a powder, dissolving 0.01 to 5 parts by weight of aluminum chloride in 1 to 30 parts by weight of deionized water to prepare an aluminum chloride solution, and then mixing the polydopamine-sericin powder and the aluminum chloride solution for reaction.

[0019] Preferably, the specific steps of step 3) are as follows: 0.01-10 parts by weight of methacrylamidophenylboronic acid and 0.01-10 parts by weight of acrylamide are added to 1-50 parts by weight of deionized water, followed by the addition of 0.001-10 parts by weight of a cross-linking agent and 0.001-10 parts by weight of an initiator, and the mixture is stirred continuously at 500-2000 rpm at 20-90° C. for 1-20 hours to obtain a mixed solution; the mixed solution is then mixed with the polydopamine-sericin-aluminum ion complex prepared in step 2), and the mixture is reacted continuously at 20-90° C. for 1-20 hours.

[0020] The sericin low hysteresis composite conductive hydrogel prepared by the above preparation method is composited by methacrylamidophenylboronic acid, acrylamide, polydopamine-modified sericin and aluminum ions.

[0021] Application of the above-mentioned sericin low hysteresis composite conductive hydrogel in hydrogel sensors.

[0022] The application of the above-mentioned sericin low hysteresis composite conductive hydrogel in flexible electronic products and wearable devices.

[0023] The principles of the present invention are as follows:

[0024] The present invention first modifies sericin with dopamine to introduce catechol groups onto its surface. The catechol groups of polydopamine and the polar groups of sericin form covalent bonds with the interface. Simultaneously, the backbone and sericin form non-covalent bonds with the interface, imparting adhesive properties to the hydrogel. Methacrylamidophenylboronic acid is copolymerized with acrylamide to introduce boronic acid groups into the polymer backbone. The boronic acid groups on the backbone react dynamically covalently with the catechol groups on the polydopamine-sericin at high temperatures to form boronate ester bonds, thereby imparting self-healing capabilities to the hydrogel. The boronate ester bonds, primarily acting as a catalyst, synergistically interact with multiple hydrogen bonds and coordination bonds to further enhance the hydrogel's self-healing efficiency. Methacrylamidophenylboronic acid, containing a carbon-carbon double bond and boronic acid groups, can be easily incorporated into the polymer chain, thereby enhancing the prepared polymer's performance. Finally, the methacrylamidophenylboronic acid-acrylamide copolymer is mixed with a polydopamine-sericin-aluminum ion complex to yield a composite conductive hydrogel. This invention transforms the sericin secondary structure from a disordered state into an α-helix and β-sheet structure through multiple hydrogen bonding and metal coordination, endowing the hydrogel with excellent low hysteresis properties. After multiple stretching cycles, the hydrogel exhibits relatively low hysteresis. Although the internal network structure is somewhat disrupted after initial stretching, the recovery and reorganization of hydrogen bonds, coordination bonds, and dynamic covalent bonds allows the hydrogel to reform into a more uniform layered cross-linked network.

[0025] The beneficial effects of the present invention are as follows:

[0026] (1) The present invention constructs a reversible cross-linked network through the synergistic effects of borate bonds (dynamic covalent bonds), metal coordination bonds (aluminum ion-catechol groups), and multiple hydrogen bonds. The borate bonds dynamically reorganize at high temperatures, giving the hydrogel efficient self-repair capabilities; the coordination bonds and hydrogen bonds accelerate local network reconstruction, significantly improving repair efficiency. Even if the sensor is damaged by external forces, the monitoring function can be fully restored after repair, significantly extending the device's service life.

[0027] (2) The present invention induces the sericin to transform from a disordered structure to an ordered α-helix / β-sheet structure through metal coordination and hydrogen bonding, forming a highly uniform layered cross-linked network that significantly reduces internal friction during cyclic deformation. After multiple stretching cycles, the hysteresis ratio is less than 5%, and the residual strain is low. This property enables the hydrogel to maintain a stable resistance response even under large deformations of the human joint (such as elbow bending), avoiding signal drift and improving sensing accuracy.

[0028] (3) The hydrogel prepared by the present invention has the advantages of strong interfacial adhesion and high sensitive sensing. The catechol groups of polydopamine and the polar groups of sericin act synergistically through covalent bonds (boronate bonds) and non-covalent bonds (hydrogen bonds, van der Waals forces), making the hydrogel closely adhere to the skin and resist sweat shedding; the dynamic network imparts high conductivity and rapid response capabilities, which can monitor human joint movements such as finger curling, wrist rotation and elbow bending in real time, providing reliable sensing support for wearable devices.

[0029] (4) The present invention uses sericin as the base material. Sericin is a natural biomass material derived from silk. It has good biodegradability, renewability and biocompatibility, is green and environmentally friendly, and can effectively reduce environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The SEM electron micrographs of the composite conductive hydrogel in Test Example 1: A is 60 μm; B is 50 μm;

[0031] Figure 2 is the infrared spectrum of the composite conductive hydrogel in Test Example 1;

[0032] Figure 3 Figure 1 shows the low hysteresis effect of the composite conductive hydrogel in Test Example 1: A is the loading-unloading curve under different tensile strains (100%, 150%, 200%, 250%, 300%, 350% and 400%); B is the corresponding hysteresis energy and hysteresis ratio;

[0033] Figure 4 This is a diagram showing the adhesion effect of the composite conductive hydrogel in Test Example 1;

[0034] Figure 5 The self-healing effect diagram of the composite conductive hydrogel in Test Example 1: A is a photograph; B is an optical microscope image;

[0035] Figure 6 This is the sensing effect diagram of the composite conductive hydrogel in Test Example 1: A is the resistance change rate with the degree of finger bending (30°, 45°, 90°); B is the resistance change rate with the degree of wrist bending (30°, 45°, 90°); C is the resistance change rate with the degree of elbow bending (30°, 45°, 90°); D is the resistance change rate for 50% strain before and after repair. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Unless otherwise specified, the technical means used in the following examples are all conventional means well known to those skilled in the art, and experimental methods without specific conditions are all conventional methods in the art.

[0038] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0039] A method for preparing a sericin low-hysteresis composite conductive hydrogel, comprising the following specific steps:

[0040] (1) Prepare a polydopamine-sericin solution, the reaction formula is shown in the following formula 1:

[0041]

[0042] First, 0.01 to 10 parts by weight of a catalyst is dissolved in 1 to 30 parts by weight of deionized water to form an aqueous solution. Then, 0.01 to 10 parts by weight of dopamine is added and stirred continuously to achieve dopamine self-polymerization. Subsequently, 0.01 to 10 parts by weight of sericin is added and stirred continuously at 500 to 2000 rpm at 20 to 80° C. for 0.5 to 20 hours to obtain a polydopamine-sericin solution.

[0043] The catalyst is one or more of hydrogen peroxide, ammonia water, triethylamine, sodium hydroxide, tetramethylethylenediamine, sodium carbonate, potassium hydroxide, acetic acid, and citric acid.

[0044] In a preferred embodiment, the catalyst is tetramethylethylenediamine.

[0045] (2) Preparation of polydopamine-sericin-aluminum ion complex

[0046] The polydopamine-sericin solution is freeze-dried for 24 to 48 hours to obtain a powder, 0.01 to 5 parts by weight of aluminum chloride is dissolved in 1 to 30 parts by weight of deionized water to prepare an aluminum chloride solution, and the polydopamine-sericin powder and the aluminum chloride solution are mixed and reacted to obtain a polydopamine-sericin-aluminum ion complex.

[0047] (3) Preparation of composite conductive hydrogel, the reaction formula is shown in the following formula 2:

[0048]

[0049] In formula 2, m and n are both natural numbers ≥1.

[0050] 0.01-10 parts by weight of methacrylamidophenylboronic acid and 0.01-10 parts by weight of acrylamide are added to 1-50 parts by weight of deionized water, followed by the addition of 0.001-10 parts by weight of a crosslinker and 0.001-10 parts by weight of an initiator. The mixture is stirred continuously at 500-2000 rpm at 20-90° C. for 1-20 hours to obtain a mixed solution (copolymer). The mixed solution is then mixed with a polydopamine-sericin-aluminum ion complex and reacted continuously at 20-90° C. for 1-20 hours to obtain the sericin low hysteresis composite conductive hydrogel.

[0051] The cross-linking agent is one or more of N,N'-methylenebisacrylamide, glutaraldehyde, N,N'-diethylbisacrylamide, acryloyloxyethyltrimethoxysilane, ethylenediamine, propylene oxide, and aluminum chloride.

[0052] In a preferred embodiment, the cross-linking agent is N,N'-methylenebisacrylamide.

[0053] The initiator is one or more of azobisisobutyronitrile, dibenzoyl peroxide, ammonium persulfate, sodium persulfate, methylbenzothiazolone, Irgacure 651, and benzophenone.

[0054] In a preferred embodiment, the initiator is ammonium persulfate.

[0055] Example 1

[0056] A method for preparing a sericin low-hysteresis composite conductive hydrogel, comprising the following specific steps:

[0057] (1) Use a pipette to measure 0.101 mL of tetramethylethylenediamine, add deionized water until the total solution reaches 10 mL, add 0.02 g of dopamine and continue stirring at room temperature to achieve dopamine self-polymerization, then add 0.4 g of sericin and magnetically stir at 800 rpm at 40°C for 2 h to obtain a polydopamine-sericin solution.

[0058] (2) The polydopamine-sericin solution was freeze-dried for 24 hours to obtain a powder, 0.25 g of aluminum trichloride was dissolved in 5 mL of deionized water, and the polydopamine-sericin powder was reacted with the aluminum trichloride solution at 30°C for 2 hours to obtain a polydopamine-sericin-aluminum ion complex.

[0059] (3) 0.2 g of methacrylamidophenylboronic acid and 3 g of acrylamide were added to a flask, 20 mL of deionized water was added, and then 0.003 g of N,N'-methylenebisacrylamide and 1 g of ammonium persulfate were added. The mixture was stirred at 800 rpm at 70 °C for 2 h to obtain a mixed solution. The solution was then mixed with a polydopamine-sericin-aluminum ion complex and reacted at 60 °C for 2 h to obtain a composite conductive hydrogel.

[0060] Example 2

[0061] A method for preparing a sericin low-hysteresis composite conductive hydrogel, comprising the following specific steps:

[0062] (1) First, weigh 0.8 g of sodium hydroxide and add deionized water until the total amount of the solution reaches 20 mL. Then, add 0.04 g of dopamine and continue stirring at room temperature to achieve dopamine self-polymerization. Then, add 0.8 g of sericin and stir magnetically at 800 rpm at 40°C for 2 h to obtain a polydopamine-sericin solution.

[0063] (2) The polydopamine-sericin solution was freeze-dried for 24 hours to obtain a powder, 0.5 g of aluminum trichloride was dissolved in 10 mL of deionized water, and the polydopamine-sericin powder was reacted with the aluminum trichloride solution at 30° C. for 2 hours to obtain a polydopamine-sericin-aluminum ion complex.

[0064] (3) 0.4 g of methacrylamidophenylboronic acid and 6 g of acrylamide were added to a flask, 40 mL of deionized water was added, and then 0.006 g of glutaraldehyde and 2 g of azobisisobutyronitrile were added. The mixture was stirred at 800 rpm at 70 °C for 2 h to obtain a mixed solution. The solution was then mixed with a polydopamine-sericin-aluminum ion complex and reacted at 60 °C for 3 h to obtain a composite conductive hydrogel.

[0065] Example 3

[0066] A method for preparing a sericin low-hysteresis composite conductive hydrogel, comprising the following specific steps:

[0067] (1) First, weigh 1 g of potassium hydroxide and add deionized water until the total volume of the solution reaches 30 mL. Then, add 0.06 g of dopamine and continue stirring at room temperature to achieve dopamine self-polymerization. Then, add 1.2 g of sericin and stir magnetically at 800 rpm at 40 °C for 2 h to obtain a polydopamine-sericin solution.

[0068] (2) The polydopamine-sericin solution was freeze-dried for 24 hours to obtain a powder. 1 g of aluminum chloride was dissolved in 15 mL of deionized water. The polydopamine-sericin powder was reacted with the aluminum chloride solution at 30° C. for 2 hours to obtain a polydopamine-sericin-aluminum ion complex.

[0069] (3) 0.6 g of methacrylamidophenylboronic acid and 9 g of acrylamide were added to a flask, 60 mL of deionized water was added, 0.009 g of ethylenediamine and 3 g of sodium persulfate were added, and the mixture was stirred at 800 rpm at 70 °C for 2 h to obtain a mixed solution. The solution was then mixed with a polydopamine-sericin-aluminum ion complex and reacted at 70 °C for 2 h to obtain a composite conductive hydrogel.

[0070] Example 4

[0071] A method for preparing a sericin low-hysteresis composite conductive hydrogel, comprising the following specific steps:

[0072] (1) Use a pipette to measure 0.3 mL of ammonia water, add deionized water until the total solution reaches 50 mL, add 0.1 g of dopamine and continue stirring at room temperature to achieve dopamine self-polymerization, then add 2 g of sericin and magnetically stir at 800 rpm at 40°C for 2 h to obtain a polydopamine-sericin solution.

[0073] (2) The polydopamine-sericin solution was freeze-dried for 24 hours to obtain a powder. 1.25 g of aluminum trichloride was dissolved in 25 mL of deionized water. The polydopamine-sericin powder was reacted with the aluminum trichloride solution at 30° C. for 2 hours to obtain a polydopamine-sericin-aluminum ion complex.

[0074] (3) 1 g of methacrylamidophenylboronic acid and 13 g of acrylamide were added to a flask, 100 mL of deionized water was added, and then 0.015 g of ethylene oxide and 5 g of dibenzoyl peroxide were added. The mixture was stirred at 800 rpm at 70 °C for 2 h to obtain a mixed solution. The solution was then mixed with a polydopamine-sericin-aluminum ion complex and reacted at 70 °C for 3 h to obtain a composite conductive hydrogel.

[0075] Example 5

[0076] A method for preparing a sericin low-hysteresis composite conductive hydrogel, comprising the following specific steps:

[0077] (1) Use a pipette to measure 0.6 mL of tetramethylethylenediamine and add deionized water until the total solution reaches 60 mL. Then add 0.12 g of dopamine and continue stirring at room temperature to achieve dopamine self-polymerization. Then add 2.4 g of sericin and stir magnetically at 800 rpm at 40°C for 2 h to obtain a polydopamine-sericin solution.

[0078] (2) The polydopamine-sericin solution was freeze-dried for 24 hours to obtain a powder. 1.5 g of aluminum trichloride was dissolved in 30 mL of deionized water. The polydopamine-sericin powder and the aluminum trichloride solution were reacted at 30° C. for 2 hours to obtain a polydopamine-sericin-aluminum ion complex.

[0079] (3) 1.2 g of methacrylamidophenylboronic acid and 18 g of acrylamide were added to a flask, 120 mL of deionized water was added, and then 0.018 g of ethylenediamine and 6 g of methylbenzothiazolone were added. The mixture was stirred at 800 rpm at 70 °C for 2 h to obtain a mixed solution. The solution was then mixed with a polydopamine-sericin-aluminum ion complex and reacted at 60 °C for 2 h to obtain a composite conductive hydrogel.

[0080] Test Example 1

[0081] The performance of the composite conductive hydrogel prepared in Example 1 was tested as follows:

[0082] (1) Scanning electron microscopy (SEM)

[0083] like Figure 1 As shown, it can be observed through a scanning electron microscope that there are a large number of pores in the cross section of the hydrogel, which means that the composite conductive hydrogel prepared by the present invention has excellent hydrophilicity.

[0084] (2) Infrared test analysis

[0085] In the preparation process of the composite conductive hydrogel, methacrylamide phenylboronic acid and acrylamide are polymerized under the action of an initiator to obtain a polymer. Infrared testing and analysis of acrylamide, methacrylamide phenylboronic acid and the polymer of the two confirms the intermolecular interactions in the polymer, such as Figure 2 As shown, the C=C peak exhibited by both acrylamide and methacrylamidophenylboronic acid disappears in the polymer, confirming the successful reaction between acrylamide and methacrylamidophenylboronic acid. The shift in the characteristic absorption peak of -B(OH)2, the C=O vibration peak, and the NH peak can also be partially attributed to the formation of strong hydrogen bonds between acrylamide and methacrylamidophenylboronic acid.

[0086] (3) Mechanical properties test

[0087] like Figure 3 As shown, at different tensile strains (100%, 150%, 200%, 250%, 300%, 350% and 400%, Figure 3 The composite conductive hydrogel prepared by the present invention has good low hysteresis performance when subjected to loading-unloading test under the strain of 100%. The loading and unloading curves of the hydrogel almost overlap after one cycle under 100% strain, with a hysteresis ratio of only 4.7% and a hysteresis energy of only 0.33 kJ / m 3 When the strain is increased to 400%, the hysteresis rate of the hydrogel can still be as low as 15%, and the hysteresis energy can reach 10.2 kJ / m 3 ( Figure 3 Middle B).

[0088] (4) Adhesion test

[0089] like Figure 4 As shown, the composite conductive hydrogel prepared by the present invention has excellent adhesion ability and can stably adhere to interfaces such as wood, iron, paper, glass, polytetrafluoroethylene, plastic, rubber and copper sheets.

[0090] (5) Self-repair test

[0091] The composite conductive hydrogel prepared by the present invention further improves its self-repairing efficiency under the main effect of borate ester bond, synergistically with multiple hydrogen bonds and coordination bonds. The self-repairing process is recorded by taking photos, such as Figure 5 As shown in Figure A, 30 minutes after the hydrogel was cut and spliced ​​together, the hydrogel was completely repaired and could be easily stretched after repair. The self-healing properties of the hydrogel were further verified by optical microscopy. Figure 5 As shown in B, a crack of 266 μm appeared after cutting. After a 30-minute repair process, the crack under an optical microscope completely overlapped, indicating that the composite conductive hydrogel prepared by the present invention achieved 100% repair.

[0092] (6) Sensor test

[0093] Conductive glue was adhered to both ends of the composite conductive hydrogel prepared in Example 1, and then one end of a wire was clamped on the conductive glue and the other end was inserted into an electrochemical workstation to assemble a simple strain sensing device.

[0094] like Figure 6 As shown in the figure, the resistance of the hydrogel attached to the human body changes with the movement of the human joints, and when the movement amplitude changes, the resistance change rate is also different, such as on the fingers ( Figure 6 Middle A), wrist ( Figure 6 Middle B) and above the elbow ( Figure 6 (C) The change rate displayed is different with different movement amplitudes. As the change amplitude increases, the hydrogel resistance increases and the change rate also increases. This also proves the excellent conductivity of the hydrogel and the good sensitivity of the sensor. In addition, after self-repair, the hydrogel can still maintain a considerable resistance change rate ( Figure 6 Middle D).

[0095] The embodiments described above are only some of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but merely represents selected embodiments of the present invention. The scope of protection of the present invention shall be based on the scope required by the claims. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a low-hysteresis composite conductive hydrogel of sericin, characterized in that: The following steps are involved: Step 1) dissolving a catalyst in deionized water to form an aqueous solution, adding dopamine and continuously stirring to allow dopamine to self-polymerize, then adding sericin and stirring to obtain a polydopamine-sericin solution; Step 2) freeze-drying the polydopamine-sericin solution prepared in step 1) to obtain a powder, which is then mixed with an aluminum chloride solution to react and obtain a polydopamine-sericin-aluminum ion complex; Step 3) adding methacrylamidophenylboronic acid and acrylamide to deionized water, then adding a crosslinking agent and an initiator, reacting to obtain a mixed solution, and then mixing the mixed solution with the polydopamine-sericin-aluminum ion complex prepared in step 2) to react, thereby obtaining the product.

2. The method for preparing a sericin low hysteresis composite conductive hydrogel according to claim 1, characterized in that: The catalyst in step 1) is one or more of hydrogen peroxide, ammonia water, triethylamine, sodium hydroxide, tetramethylethylenediamine, sodium carbonate, potassium hydroxide, acetic acid, and citric acid.

3. The method for preparing a sericin low hysteresis composite conductive hydrogel according to claim 1, characterized in that: In step 3), the cross-linking agent is one or more of N,N'-methylenebisacrylamide, glutaraldehyde, N,N'-diethylbisacrylamide, acryloyloxyethyltrimethoxysilane, ethylenediamine, propylene oxide, and aluminum chloride.

4. The method for preparing a sericin low hysteresis composite conductive hydrogel according to claim 1, wherein: In step 3), the initiator is one or more of azobisisobutyronitrile, dibenzoyl peroxide, ammonium persulfate, sodium persulfate, methylbenzothiazolone, Irgacure 651, and benzophenone.

5. The method for preparing a sericin low hysteresis composite conductive hydrogel according to claim 1, wherein: The specific steps of step 1) are as follows: first, 0.01 to 10 parts by weight of a catalyst is dissolved in 1 to 30 parts by weight of deionized water to form an aqueous solution, then 0.01 to 10 parts by weight of dopamine is added and stirred continuously to achieve dopamine self-polymerization, and then 0.01 to 10 parts by weight of sericin is added and stirred continuously at 500 to 2000 rpm at 20 to 80° C. for 0.5 to 20 hours.

6. The method for preparing a sericin low hysteresis composite conductive hydrogel according to claim 5, characterized in that: The specific steps of step 2) are as follows: freeze-dry the polydopamine-sericin solution prepared in step 1) for 24 to 48 hours to obtain a powder, dissolve 0.01 to 5 parts by weight of aluminum chloride in 1 to 30 parts by weight of deionized water to prepare an aluminum chloride solution, and then mix the polydopamine-sericin powder and the aluminum chloride solution for reaction.

7. The method for preparing a sericin low hysteresis composite conductive hydrogel according to claim 6, characterized in that: The specific steps of step 3) are as follows: 0.01-10 parts by weight of methacrylamidophenylboronic acid and 0.01-10 parts by weight of acrylamide are added to 1-50 parts by weight of deionized water, followed by the addition of 0.001-10 parts by weight of a crosslinker and 0.001-10 parts by weight of an initiator, and the mixture is stirred continuously at 500-2000 rpm at 20-90° C. for 1-20 hours to obtain a mixed solution; the mixed solution is then mixed with the polydopamine-sericin-aluminum ion complex prepared in step 2), and the mixture is reacted continuously at 20-90° C. for 1-20 hours.

8. The sericin low hysteresis composite conductive hydrogel prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The hydrogel is composited by methacrylamidophenylboronic acid, acrylamide, polydopamine-modified sericin and aluminum ions.

9. Use of the sericin low hysteresis composite conductive hydrogel according to claim 8 in a hydrogel sensor.

10. Use of the sericin low hysteresis composite conductive hydrogel according to claim 8 in flexible electronic products and wearable devices.

Images