Silk fibroin-based topological structure conductive hydrogel and preparation method and application thereof

Abstract

The application relates to the technical field of flexible electronic materials, and discloses a silk fibroin-based topological structure conductive hydrogel as well as a preparation method and application thereof, which is composed of the following components: rGO@SilMA is used as a polymerization main body, wherein the rGO@SilMA is formed by mixing silk fibroin and graphene oxide dispersion liquid and reacting in the presence of glyceryl methacrylate, polyethylene glycol diacrylate is used as a reinforcing phase, phenyl-2,4,6-trimethylbenzoyl lithium phosphate (LAP) is used as a photoinitiator, and the mass proportion of each component in the photocuring ink is as follows: rGO@SilMA 20%, PEGDA 10%, and LAP 0.75%. The application significantly improves the mechanical properties and sensing stability of the hydrogel by constructing an rGO@SilMA-PEGDA interpenetrating network structure and introducing a TPMS topological design; the interpenetrating network improves the compression modulus and keeps a high level of elongation at break, thereby meeting the requirements of a high deformation scene; and the negative Gaussian curvature characteristics of the topological structure make the stress distribution more uniform, thereby increasing an effective sensing area.

Description

Technical Field

[0001] This invention relates to the field of flexible electronic materials technology, specifically to a silk fibroin-based topological conductive hydrogel, its preparation method, and its application. Background Technology

[0002] Flexible conductive hydrogels, as a type of functional material that combines biocompatibility and electroresponsiveness, have shown broad application prospects in wearable health monitoring devices, human-computer interaction systems, and flexible robots. Among them, hydrogels based on natural biopolymers have become a core material choice for skin electronic devices and implantable sensing devices due to their excellent biocompatibility.

[0003] Silk fibroin (SF), a natural protein, possesses a unique β-sheet crystalline structure and good biocompatibility. After modification, it can form a stable three-dimensional network structure. SilMA, obtained through methacrylation modification, not only retains the original bioactivity of silk fibroin but also introduces photocrosslinkable acrylate groups, making it suitable for precision 3D printing technology. However, the single SilMA network has limitations in mechanical properties; its fracture strain and elastic modulus are insufficient to meet the requirements of high-deformation applications.

[0004] In existing technologies, researchers often employ composite modification strategies to improve the performance of silk fibroin hydrogels, but many problems still exist: some schemes use toxic crosslinking agents such as glutaraldehyde, which poses a risk of cytotoxicity; conductive fillers such as graphene oxide (GO) are prone to aggregation in hydrogels, resulting in uneven conductivity; most hydrogels are two-dimensional structures or rely on mold forming, with simple structural designs, making it difficult to achieve precise preparation of complex three-dimensional topological structures.

[0005] 3D printing technology, especially digital light processing (DLP) photopolymerization technology, has made it possible to prepare complex hydrogel structures due to its advantages such as high printing accuracy and fast forming speed. However, the printing resolution of existing silk fibroin-based hydrogel inks is insufficient, and it is difficult to balance the mechanical properties and electrical conductivity stability of the formed hydrogel, which limits its application in the field of high-precision sensing.

[0006] Therefore, it is of great significance to develop a silk fibroin-based topological conductive hydrogel that combines high printing accuracy, excellent mechanical properties, and stable conductivity. Summary of the Invention

[0007] The purpose of this invention is to provide a silk fibroin-based topological conductive hydrogel, its preparation method, and its application in order to solve the above-mentioned problems.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A silk fibroin-based topologically conductive hydrogel, composed of the following components:

[0010] rGO@SilMA (reduced graphene oxide-methacrylamide silk fibroin composite system) is used as the main polymer, wherein rGO@SilMA is formed by mixing silk fibroin with graphene oxide (GO) dispersion and reacting it in the presence of glyceryl methacrylate (GMA);

[0011] Polyethylene glycol diacrylate (PEGDA) is the reinforcing phase;

[0012] Lithium phenyl-2,4,6-trimethylbenzoyl phosphate (LAP) is a photoinitiator;

[0013] The mass percentages of each component in the photocurable ink are: rGO@SilMA 20%, PEGDA 10%, LAP 0.75%; the hydrogel has a Gyroid (G), Diamond (D), or Schwarz (S) topology.

[0014] A method for preparing a silk fibroin-based topologically conductive hydrogel, based on the silk fibroin-based topologically conductive hydrogel of claim 1, includes the following steps:

[0015] S1: Extraction and degumming of silk fibroin: Add 40g of raw silk to 2L of boiling water containing 10g of anhydrous sodium carbonate and boil for 30 minutes. After taking it out, wash it repeatedly with deionized water 3 times. After drying, repeat the degumming step 3 times to obtain degummed silk fibroin.

[0016] S2: Preparation of rGO@SilMA solution: Dissolve 20g of degummed silk fibroin in 100mL of 9.3M lithium bromide solution, heat at 60℃ for 1h and stir every 20min; add 100mL of GO dispersion and 6mL of LGMA, and stir at 300r / min at 60℃ for 6h.

[0017] The reaction solution was flow dialyzed for 24 hours using a dialysis bag with a molecular weight cutoff of 12-14 kDa, filtered three times through a filter cloth and a 150-mesh filter, and then freeze-dried at -80°C for 5 days to obtain rGO@SilMA dry powder.

[0018] S3: Preparation of UV-curable ink: Mix 2.7 mL of distilled water with 0.3 mL of PEGDA, add 0.0225 g of LAP and stir in the dark until dissolved, then add 0.6 g of GO@SilMA dry powder and stir at 300 r / min until completely dissolved to obtain rGO@SilMA-PEGDA UV-curable ink;

[0019] S4: 3D printing of topological hydrogels: designing G, D or S topological model;

[0020] Injecting photocurable ink into the feed tank of a DLP printer and printing is performed. After printing, the sample is cleaned with deionized water to obtain the target hydrogel.

[0021] Preferably, the concentration of the GO dispersion in step S2 is 0.5% w / v, and the reduction reaction is achieved through tyrosine residues in silk fibroin.

[0022] Preferably, the molecular weight of the PEGDA in step S3 is 700 Da.

[0023] Preferably, the topological model described in step S4 is designed using nTop software, and the unit cell size is 16×10×2mm.

[0024] Preferably, the parameters for DLP printing in step S4 are: light intensity 15-20mW / cm², slice thickness 15μm, stretching speed 3-6mm / min, and exposure time 2-8s.

[0025] Application of a silk fibroin-based topological conductive hydrogel in the fabrication of wearable biosensors, human-computer interaction devices, or flexible electronic devices.

[0026] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0027] 1. This invention significantly improves the mechanical properties and sensing stability of hydrogels by constructing an rGO@SilMA-PEGDA interpenetrating network structure and introducing TPMS topology design. The interpenetrating network increases the compressive modulus while maintaining a high level of elongation at break, meeting the requirements of high deformation scenarios. The negative Gaussian curvature of the topology structure makes the stress distribution more uniform and increases the effective sensing area.

[0028] 2. This invention utilizes the in-situ reduction of GO by silk fibroin tyrosine residues to form rGO conductive pathways. Combined with DLP high-precision printing technology, it improves sensor sensitivity (GF) and achieves printing accuracy down to the micrometer level, enabling precise molding of complex three-dimensional structures. This not only solves the problem of uneven conductivity in traditional hydrogels but also expands its application scenarios in the fields of biomedicine and flexible electronics. Attached Figure Description

[0029] Figure 1 A schematic diagram illustrating the response of the relative change rate of resistance of hydrogels with different topologies (G, D, S) according to embodiments of the present invention is shown.

[0030] Figure 2 The diagram illustrates the resistivity response speed and cycling stability of hydrogels with different topologies (G, D, S) according to embodiments of the present invention.

[0031] Figure 3 A schematic diagram illustrating the application of hydrogels with different topological structures (G, D, S) according to embodiments of the present invention in the fields of human physiological signal monitoring and speech recognition is shown.

[0032] Figure 4 A schematic diagram illustrating the application of hydrogels with different topological structures (G, D, S) according to embodiments of the present invention in the field of wearable motion monitoring is shown.

[0033] Figure 5 The illustration shows a schematic diagram demonstrating the application of hydrogels with different topological structures (G, D, S) according to embodiments of the present invention in the field of novel interactions in wearable devices. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] Raw material dosage: 40g raw silk, 10g anhydrous sodium carbonate, 100mL 9.3M lithium bromide solution, 100mL 0.5% w / v GO dispersion, 6mL glyceryl methacrylate (GMA), 0.3mL PEGDA with a molecular weight of 700Da, 0.0225g LAP, and appropriate amount of deionized water.

[0037] Preparation process: The preparation steps were performed according to the invention. First, silk fibroin was extracted and degummed to obtain approximately 25g of degummed silk fibroin. Then, an rGO@SilMA solution was prepared, and after degumming, dissolving, reacting, dialysis, filtering, and freeze-drying, rGO@SilMA dry powder was obtained. Next, a photocurable ink was prepared by mixing and dissolving the rGO@SilMA dry powder, PEGDA, and LAP in a specific ratio. Finally, a Gyroid (G) topological structure model was designed using nTop software, and the DLP printing parameters were set as follows: light intensity 18mW / cm², exposure time 5s, and stretching speed 4.5mm / min. The resulting G-structure silk fibroin-based topological conductive hydrogel was printed.

[0038] Example 2

[0039] Raw material usage: Same as in Example 1.

[0040] Preparation process: The extraction and degumming of silk fibroin, the preparation of rGO@SilMA solution, and the formulation of photocurable ink were all the same as in Example 1. A Diamond (D) topological model was designed using nTop software, and the DLP printing parameters were the same as in Example 1, resulting in a D-structure silk fibroin-based topological conductive hydrogel.

[0041] Example 3

[0042] Raw material usage: Same as in Example 1.

[0043] Preparation process: The extraction and degumming of silk fibroin, the preparation of rGO@SilMA solution, and the formulation of photocurable ink were all the same as in Example 1. A Schwarz (S) topological model was designed using nTop software, and the DLP printing parameters were the same as in Example 1, resulting in an S-structure silk fibroin-based conductive hydrogel.

[0044] Comparative Example 1

[0045] Raw material dosage: Compared with Example 1, PEGDA was not added, while the dosage of other raw materials was the same.

[0046] Preparation process: The preparation steps of Example 1 were followed, except that PEGDA was not added in the photocurable ink preparation step.

[0047] Comparative Example 2

[0048] Raw material dosage: Compared with Example 1, no GO dispersion was added, and the dosage of other raw materials was the same.

[0049] Preparation process: The preparation steps of Example 1 were followed, except that no GO dispersion was added in the preparation steps of rGO@SilMA solution.

[0050] Comparative Example 3

[0051] Raw material usage: Same as in Example 1.

[0052] Preparation process: The extraction and degumming of silk fibroin, the preparation of rGO@SilMA solution, and the formulation of photocurable ink were all the same as in Example 1. The photocurable ink was poured into a conventional mold and cured under the same lighting conditions as in Example 1, without using DLP 3D printing or topology design.

[0053] Performance testing

[0054] Mechanical property testing: The compressive modulus and fracture strain of the hydrogel were tested using a universal testing machine, and the test data were recorded in accordance with relevant standard methods.

[0055] Conductivity and Sensitivity Testing: The resistance change of the hydrogel under different strains was measured by the four-probe method, and the relative rate of change of resistance and sensitivity (GF) were calculated to analyze its conductivity and sensing sensitivity.

[0056] Response speed and cycle stability testing: A dynamic mechanical analyzer and an electrochemical workstation were used to test the response time and recovery time of the hydrogel under external force, as well as the performance changes after multiple cycles.

[0057] The test results are shown in the table below:

[0058]

[0059] The test results show that the silk fibroin-based topological conductive hydrogels obtained in Examples 1-3 are superior to those in Comparative Examples 1-3 in terms of compressive modulus, fracture strain, sensitivity, response speed, and cycle stability. The compressive modulus of Examples 1-3 is significantly higher than that of Comparative Example 1 because the addition of PEGDA forms an interpenetrating network structure, effectively improving the mechanical properties of the hydrogel. Compared to Comparative Example 2, Examples 1-3 show a significant improvement in sensitivity due to the addition of GO dispersion and the achievement of uniform dispersion of rGO. Comparative Example 3, lacking topological structure design and 3D printing technology, exhibits inferior response speed and cycle stability compared to the Examples. This fully verifies the effectiveness and superiority of the technical solution of this invention.

[0060] GO is covalently reduced through amino acid residues on silk fibroin during SiIMA dialysis, which is why it is conductive, and the reaction conditions are also very mild.

[0061] application

[0062] The silk fibroin-based topological conductive hydrogel prepared by this invention has important application value in multiple fields.

[0063] Appendix Figure 1 (a) shows the relationship between strain and resistance rate of structure G, (b) shows the relationship between strain and resistance rate of structure D, (c) shows the relationship between strain and resistance rate of structure S, (d) shows the relationship between pressure and resistance rate of structure G, (e) shows the relationship between pressure and resistance rate of structure D, and (f) shows the relationship between pressure and resistance rate of structure S.

[0064] The AC data shows that the relative rate of change of resistance for all three structures increases with increasing strain: the G structure responds rapidly in the low-strain region, then stabilizes, eventually reaching approximately 70%; the D structure changes gradually, also eventually reaching 70%; the S structure shows a similar trend to the G structure, but ultimately slightly below 70%, indicating that all three can respond to strain, but the response rate and amplitude differ. The DF data shows that under pressure, the G structure exhibits a good linear relationship between the rate of change of resistance and pressure in the low-pressure region (0-600 Pa), stabilizing beyond that pressure; the D structure's rate of change of resistance increases slowly and remains linear even in the high-pressure region; the S structure responds rapidly in the low-pressure region, stabilizing after reaching a certain pressure.

[0065] In the field of human body signal detection, the G, D, and S topologies each have their advantages: the G structure is sensitive to low-strain and low-pressure signals and responds quickly, making it suitable for detecting weak signals such as pulse or muscle contraction, and can be integrated into wearable devices to monitor physiological parameters in real time; the D structure has a slower response but a wide linear range, making it suitable for monitoring continuous and gradual pressure signals (such as the pressure distribution from prolonged sitting), which helps prevent health problems; the S structure responds quickly under low pressure and can detect sudden, instantaneous pressure (such as impact from exercise), and can be applied to early warning systems in protective equipment. The characteristic analysis of these structures provides new material and structural options for human body signal detection technology.

[0066] Appendix Figure 2 In the table, (a) represents the resistance response speed of structure G, (b) represents the resistance stability of structure G, (c) represents the resistance change rate of structure G with strain (10%, 20%, 30%), (d) represents the resistance response speed of structure D, (e) represents the resistance stability of structure D, (f) represents the resistance change rate of structure D with strain (10%, 20%, 30%), (g) represents the resistance response speed of structure S, (h) represents the resistance stability of structure S, and (i) represents the resistance change rate of structure S with strain (10%, 20%, 30%).

[0067] A 16×10×2mm sheet-like structure was constructed, which offers greater flexibility and thinness, allowing it to better conform to the curves of the human body and significantly improve wearing comfort. It also contributes to improved signal acquisition stability and accuracy. Regarding response time, the G structure (105ms response / 440ms recovery) is suitable for capturing transient signals; the D structure (171ms response / 258ms recovery) is more suitable for monitoring regular signals; and the S structure (167ms response / 21ms recovery) performs excellently in rapid and frequent detection scenarios. Cyclic stability testing shows that the G structure maintains good short-term stability within 1000 cycles, the D structure exhibits stable fluctuations suitable for long-term monitoring, and the S structure remains stable even after 10,000 cycles. In summary, the G structure is suitable for detecting sudden, transient signals (such as transient physiological changes), the D structure is suitable for continuous daily monitoring (such as sports and health tracking), and the S structure, with its rapid response, ultra-short recovery, and excellent long-term stability, can meet the needs of high-precision medical monitoring (such as chronic disease management).

[0068] Appendix Figure 3 (a) shows swallowing monitoring, and (b) shows speech recognition.

[0069] G-structure conductive hydrogels have demonstrated significant application value in the fields of human physiological signal monitoring and speech recognition. In physiological monitoring, this hydrogel, by adhering to the neck, detects real-time changes in resistance caused by swallowing movements. This monitoring method is non-invasive and real-time, making it applicable to medical rehabilitation, providing objective data support for evaluating the rehabilitation training effects of patients with swallowing dysfunction, and serving as an auxiliary tool for clinical diagnosis of swallowing abnormalities. In speech recognition, this hydrogel can accurately distinguish the resistance change characteristics of the pronunciation of the numbers 1 to 9, and can be used as a novel speech sensing material in wearable interactive devices, such as smart home control and non-contact human-computer interaction systems in special environments (such as high-noise or hand-operated scenarios), offering advantages in efficiency and accuracy.

[0070] Appendix Figure 4 (a) indicates the good deformation rate and elastic recovery of the ring-shaped topological conductive hydrogel, and (b) indicates the signal generated by the ring-shaped topological conductive hydrogel when the finger is bent.

[0071] The ring-shaped, D-structure conductive hydrogel can monitor finger flexion and movement in real time through changes in resistance. When a finger bends, the hydrogel stretches and deforms, changing its resistance accordingly. By analyzing the rate of change of resistance curve, finger movements can be accurately tracked. This characteristic makes it widely applicable in wearable motion monitoring, such as enabling precise hand motion capture in virtual reality (VR) interactive devices to enhance the immersive experience; and in the field of medical rehabilitation, it can quantify and evaluate hand training data, providing objective evidence for doctors to develop personalized rehabilitation plans.

[0072] Appendix Figure 5 (a) shows the conductive hydrogel that can adhere to the copper foil after being soaked in tannic acid (TA), (bc) shows the electronic keyboard adhering to the skin, (d) is a schematic diagram of the electronic keyboard structure, and (e) shows the different resistance signals that appear when the electronic keyboard is pressed.

[0073] S-structure conductive hydrogels can be used to control sensing performance by adjusting structural parameters (such as wall thickness), and can be made into electronic keyboards that adhere to the skin. When the same pressure is applied to different locations, the hydrogel will produce different resistance changes, which are then converted into electrical signals to realize command input. This design provides a new interaction method for wearable devices (such as smart bracelets and smart clothing), allowing for convenient operation without traditional input devices, significantly enhancing the practicality and functionality of wearable technology.

[0074] The above description of the embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a silk fibroin-based topologically conductive hydrogel, characterized in that, The silk fibroin-based topologically conductive hydrogel is composed of the following components: a reduced graphene oxide-methacrylated silk fibroin composite system rGO@SilMA as the polymer matrix, wherein rGO@SilMA is formed by mixing silk fibroin with a graphene oxide (GO) dispersion and reacting it in the presence of glyceryl methacrylate (GMA); polyethylene glycol diacrylate (PEGDA) as the reinforcing phase; and lithium phenyl-2,4,6-trimethylbenzoyl phosphate (LAP) as the photoinitiator. The mass percentages of each component in the photocurable ink are: rGO@SilMA 20%, PEGDA 10%, and LAP 0.75%. The hydrogel has a Gyroid, Diamond, or Schwarz topology. The silk fibroin-based topologically conductive hydrogel was prepared using the following method: S1: Extraction and degumming of silk fibroin: Add 40g of raw silk to 2L of boiling water containing 10g of anhydrous sodium carbonate and boil for 30 minutes. After taking it out, wash it repeatedly with deionized water 3 times. After drying, repeat the degumming step 3 times to obtain degummed silk fibroin. S2: Preparation of rGO@SilMA solution: Dissolve 20g of degummed silk fibroin in 100mL of 9.3M lithium bromide solution, heat at 60℃ for 1h and stir every 20min; add 100mL of GO dispersion and 6mL of LGMA, and stir at 300r / min at 60℃ for 6h. The reaction solution was flow dialyzed for 24 hours using a dialysis bag with a molecular weight cutoff of 12-14 kDa, filtered three times through a filter cloth and a 150-mesh filter, and then freeze-dried at -80°C for 5 days to obtain rGO@SilMA dry powder. S3: Preparation of UV-curable ink: Mix 2.7 mL of distilled water with 0.3 mL of PEGDA, add 0.0225 g of LAP and stir in the dark until dissolved, then add 0.6 g of GO@SilMA dry powder and stir at 300 r / min until completely dissolved to obtain rGO@SilMA-PEGDA UV-curable ink; S4: 3D printing of topological hydrogels: designing Gyroid, Diamond, or Schwarz topological models; Injecting photocurable ink into the feed tank of a DLP printer and printing is performed. After printing, the ink is washed with deionized water to obtain a hydrogel with a Gyroid, Diamond, or Schwarz topology.

2. The method for preparing a silk fibroin-based topologically conductive hydrogel according to claim 1, characterized in that, The concentration of the GO dispersion in step S2 is 0.5% w / v, and the reduction reaction is achieved through tyrosine residues in silk fibroin.

3. The method for preparing a silk fibroin-based topologically conductive hydrogel according to claim 1, characterized in that, The molecular weight of PEGDA mentioned in step S3 is 700 Da.

4. The method for preparing a silk fibroin-based topologically conductive hydrogel according to claim 1, characterized in that, The topological model described in step S4 was designed using nTop software, with a unit cell size of 16×10×2mm.

5. The method for preparing a silk fibroin-based topologically conductive hydrogel according to claim 1, characterized in that, The parameters for DLP printing in step S4 are: light intensity 15-20mW / cm², slice thickness 15μm, pulling speed 3-6mm / min, and exposure time 2-8s.

6. The application of a silk fibroin-based topological conductive hydrogel prepared by any one of claims 1 to 5 in the preparation of wearable biosensors and human-computer interaction devices.

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