Multifunctional polyvinyl alcohol-based hydrogel and preparation method and application thereof

Abstract

The application discloses a multifunctional polyvinyl alcohol-based hydrogel and a preparation method and application thereof, and belongs to the technical field of high polymer hydrogel material preparation.The hydrogel takes polyvinyl alcohol (PVA) as a base material, takes polydopamine-coated sea squirt nanocellulose (PDA@TCNCs), beta-glycerophosphate sodium (GP) and phytic acid (PA) as functional components; the mass-volume ratio of PVA, PDA@TCNCs, GP and PA aqueous solutions is 2.62g:0.05g-0.25g:1.0g:4mL-12mL.The hydrogel has excellent mechanical properties, anti-swelling properties and antibacterial properties, and has good biocompatibility, and has wide application prospects in wearable strain sensors, underwater motion monitoring and triboelectric nanogenerators and other fields.

Description

Technical Field

[0001] This invention belongs to the field of polymer hydrogel material preparation technology, and relates to a multifunctional polyvinyl alcohol-based hydrogel, its preparation method and application. Background Technology

[0002] In recent years, hydrogel electronic skin has attracted widespread research attention in fields such as health management, human-machine interfaces, and flexible sensors due to its flexibility, sensitivity, biocompatibility, and scalability. The preparation of conductive hydrogels typically involves cross-linking via metal coordination, Schiff base reactions, or multiple hydrogen bonds. Furthermore, to increase the conductivity of conductive hydrogels, additives such as Mexene30, rGOs31, and CNTs32 can be added.

[0003] However, the fabrication of these multifunctional conductive hydrogels typically requires multiple synthesis steps and the addition of high-value fillers, resulting in complex and costly manufacturing processes. The application of flexible electronic devices in underwater environments has attracted widespread attention; however, signal distortion and performance degradation caused by the expansion of conductive hydrogels in aquatic environments limit their further applications.

[0004] Furthermore, the mechanical properties and conductivity sensitivity of conductive hydrogels need to be balanced. Most traditional conductive hydrogels suffer from insufficient mechanical strength, poor fatigue resistance, narrow response range, easy signal interruption, short lifespan, and non-recyclability. Additionally, hydrogels that come into direct contact with human skin need to possess antibacterial properties to prevent skin damage.

[0005] Therefore, the preparation of multifunctional hydrogel sensors with photothermal properties, anti-swelling properties, high conductivity, recyclability, good mechanical properties, and antibacterial properties has great practical significance. Summary of the Invention

[0006] In view of this, the present invention provides a multifunctional polyvinyl alcohol-based hydrogel. The hydrogel provided by the present invention has excellent mechanical properties, anti-swelling properties, and antibacterial properties, while also exhibiting good biocompatibility, and has broad application prospects in wearable strain sensors, underwater motion monitoring, and triboelectric nanogenerators.

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

[0008] The hydrogel uses polyvinyl alcohol (PVA) as the matrix material and polydopamine-encapsulated sea squirt nanocellulose (PDA@TCNCs), sodium β-glycerophosphate (GP), and phytic acid (PA) as functional components. The mass-volume ratio of PVA, PDA@TCNCs, GP, and PA aqueous solutions is 2.62 g: 0.05 g~0.25 g: 1.0 g: 4 mL~12 mL. The mass concentration of the PA aqueous solution is 50%.

[0009] The beneficial effects of the above technical solution: Phytic acid (PA), also known as inositol hexaphosphate, is a non-toxic natural organic macromolecule isolated from plants. The abundant hydroxyl groups in PA make it an effective gelling agent for PVA hydrogels. Phytic acid not only establishes strong hydrogen bonds with the PVA chains themselves but also enhances the hydrogen bond interactions between PVA chains. This method effectively alleviates the problem of poor mechanical properties commonly found in PVA hydrogels. Improving the mechanical and detection performance of flexible sensors is a top priority in current research. Because PA is strongly acidic, the dissolution of PA in H2O will generate a large amount of H2O. + This significantly improves the conductivity of the hydrogel, enabling it to accurately detect signals of minimum intensity.

[0010] Polydopamine (PDA), with its molecular structure containing multiple primary amine groups and phenolic hydroxyl groups, is a biomaterial possessing free radical scavenging, UV shielding, and good biocompatibility. Furthermore, PDA exhibits broadband infrared light absorption and efficient thermal conversion properties, enabling it to kill bacteria through heating, making it an innovative and highly effective antibacterial agent. Cellulose nanocrystals (TCNCs) are abundant in nature. Compared to other cellulose nanocrystals derived from plants or bacteria, TCNCs possess higher Young's modulus and aspect ratio. TCNCs can promote the formation of permeable networks, enhance stress transfer in composite materials, and thus improve the mechanical properties of hydrogels. Moreover, TCNCs, derived from nature, exhibit better biocompatibility compared to other types of nanocellulose.

[0011] The structural formula of the multifunctional polyvinyl alcohol-based hydrogel with photothermal properties, anti-swelling properties, and high electrical conductivity provided by this invention can be found in the appendix to this specification. Figure 1 From the appendix Figure 1It was found that the natural acidic environment of phytic acid endows the hydrogel with excellent antibacterial effects; the salting-out effect induced by sodium β-glycerophosphate and the multiple hydrogen bond network densify the hydrogel structure, giving it excellent anti-swelling properties, allowing it to be used as a sensor to stably detect the movement of marine organisms in seawater; the strong hydrogen bond network formed by phytic acid and water molecules gives the hydrogel excellent antifreeze properties, allowing it to maintain flexibility and conductivity even at low temperatures. The photothermal properties of this hydrogel originate from polydopamine-encapsulated sea squirt cellulose nanoparticles. The chemical structure of polydopamine is similar to that of natural melanin, also exhibiting broadband light absorption and efficient photothermal conversion characteristics. The phenolic hydroxyl and amino groups on the surface of polydopamine-encapsulated sea squirt cellulose nanoparticles form hydrogen bonds with the phosphate groups of phytic acid, and the sea squirt cellulose nanoparticles, acting as a nano-reinforcing phase, further enhance mechanical strength through physical entanglement. Phytic acid dissociates in water to generate a large number of hydrogen ions, providing abundant ion transport carriers and endowing the polyvinyl alcohol-based hydrogel with high conductivity.

[0012] Preferably, the polyvinyl alcohol has a structure as shown in general formula 1:

[0013] General Formula 1 In the formula, n is 1700; and the degree of alcoholysis of the polyvinyl alcohol is >98%.

[0014] Preferably, the mass-to-volume ratio of the PVA, PDA@TCNCs, GP, and PA aqueous solution is 2.62 g: 0.1 g: 1.0 g: 8.0 mL.

[0015] This invention also provides a method for preparing the above-mentioned multifunctional polyvinyl alcohol-based hydrogel, comprising the following steps: (1) Dissolve PDA@TCNCs in deionized water, stir overnight and sonicate to obtain PDA@TCNCs suspension; (2) Add PA aqueous solution and PVA sequentially to the PDA@TCNCs suspension in step (1), and heat in a water bath to obtain mixture A; (3) Dissolve GP in deionized water, add it to the mixture A described in step (2) after dissolution, and heat it in a water bath to obtain the mixed precursor solution; (4) After degassing the mixed precursor liquid, inject it into the mold, freeze it at -80℃ for 8-12 hours, and then thaw it at room temperature for 3-6 hours; (5) Repeat the freezing-thawing process 2-4 times to obtain the multifunctional polyvinyl alcohol-based hydrogel.

[0016] Preferably, the mixed precursor liquid is degassed and injected into a mold, frozen at -80°C for 10 hours, and then thawed at room temperature for 4 hours. The freezing-thawing process is repeated 3 times.

[0017] Preferably, the preparation method of PDA@TCNCs is as follows: thallusin is isolated from true sea squirts and hydrolyzed with sulfuric acid. After standing, it is centrifuged and then dialyzed with deionized water until neutral. Then, it is concentrated by vacuum rotary evaporation to obtain a uniform sea squirt nanocellulose suspension with a concentration of 1.0 wt%. The TCNCs suspension is dispersed in Tris buffer, dopamine hydrochloride is added, and oxidative polymerization is carried out at pH = 8.5 for 12-24 hours. After centrifugation and washing, polydopamine-coated sea squirt nanocellulose PDA@TCNCs are obtained.

[0018] Preferably, in step (1), the mass-to-volume ratio of PDA@TCNCs to deionized water is (0.05~0.25) g: (5~12) mL; more preferably, it is 0.1 g: 9 mL.

[0019] Preferably, in step (2), the water bath heating temperature is 95°C and the time is 2 hours.

[0020] Preferably, in step (3), the mass-to-volume ratio of GP to deionized water is 1 g: 2 mL; the water bath heating temperature is 95 °C and the time is 30 min.

[0021] Another object of the present invention is to provide the application of the above-mentioned multifunctional polyvinyl alcohol-based hydrogel in the field of sensing.

[0022] Preferably, the hydrogel is used in the fields of wearable strain sensors, underwater motion monitoring sensors, and triboelectric nanogenerators.

[0023] The beneficial effects of this invention are: 1. The raw materials used in this invention, polyvinyl alcohol and PDA@TCNCs, are inexpensive and readily available, possess good biocompatibility and biodegradability, and are safe and environmentally friendly to use. Furthermore, PDA@TCNCs have a high aspect ratio and mechanical modulus, making them ideal nano-reinforced fillers.

[0024] 2. This invention uses a purely physical cross-linking salt-freeze-thaw method, which is mild, requires no toxic reagents or complex post-processing, is suitable for large-scale production, and has mild reaction conditions, high system purity and tolerance, low cost and easy operation.

[0025] 3. The hydrogel prepared by this invention has excellent comprehensive properties, making it a promising candidate for application in many cutting-edge fields such as wearable electronics, underwater exploration, blue energy, soft robots, and triboelectric nanogenerators.

[0026] The above-mentioned superior features indicate that this invention is suitable for industrial production and has broad application prospects. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of the hydrogel prepared in this invention.

[0029] Figure 2 This is a scanning electron microscope (SEM) image of the PDA@TCNCs prepared in Example 1 of the present invention.

[0030] Figure 3 The above are the infrared (FT-IR) spectra of the reactants and products in Example 1 of this invention.

[0031] Figure 4 The image shows the photothermal properties of the hydrogel prepared in Example 1 of this invention.

[0032] Figure 5 This is a schematic diagram illustrating the anti-swelling properties of the hydrogel and PVA prepared in Example 1 of the present invention.

[0033] Figure 6 The tensile stress-strain curves are for the hydrogels prepared in Examples 1-5 of this invention.

[0034] Figure 7 The above are signal diagrams of the hydrogels prepared in Examples 1 and 6-9 of this invention under different strain conditions.

[0035] Figure 8 The images show the colony growth of Staphylococcus aureus and Escherichia coli after different treatments in Experiment 7; (a) is a picture of the colony culture dish; and (b) is a bar chart comparing the bacterial counts under different treatments.

[0036] Figure 9 The results of the cytotoxicity test of the hydrogel in Example 8 are shown in (a) and (b) are microscopic images of 3T3 cells co-cultured with the hydrogel prepared in Example 1. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The reagents and raw materials used in the examples are as follows: Reagent: Polyvinyl alcohol (PVA; Type: 1799; Degree of alcoholysis: 98~99% (mol / mol); CAS No.: 9002-89-5; Molecular weight: 76000 g mol -1 ), analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0039] Dopamine hydrochloride (CAS No.: 62-31-7; Molecular formula: C8H) 11 NO2 HCl; Molecular weight: 189.64 g mol -1 ), 98% purity, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0040] Pharmaceutical: Phytic acid 50wt% solution (PA), analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0041] β-Glycerophosphate sodium pentahydrate (GP), analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0042] Other materials: distilled water (H2O, resistivity 18.3 MΩ), prepared in the laboratory. All reagent dissolution and experimental procedures were performed using the above-mentioned deionized water.

[0043] Example 1 A method for preparing a multifunctional polyvinyl alcohol-based hydrogel with photothermal properties, anti-swelling properties, and high electrical conductivity, specifically includes the following steps: Step (1): Separate the tunicin from the true sea squirt and hydrolyze it with 60% sulfuric acid. After standing for a period of time, centrifuge it and then dialyze it with deionized water until neutral. After vacuum rotary evaporation, concentrate it to obtain a uniform sea squirt nanocellulose suspension (1.0 wt%). Step (2): Dilute 30.0 g of sea squirt nanocellulose suspension (1.0 wt%) with deionized water to 150 mL, and stir vigorously under ultrasonic treatment to ensure homogeneity. Then, add Tris buffer solution (1 mol·L⁻¹). -1 The pH was adjusted to 8.5. Then, 0.3 g of dopamine hydrochloride was added. The synthesis reaction was carried out in an ultrasonic cleaning tank for 30 min, followed by stirring at room temperature for 24 h. The color of the suspension changed from white to pink, and then to black. The reaction solution was repeatedly centrifuged at 9000 rpm and washed several times with deionized water to obtain polydopamine-coated tunicate cellulose nanoparticles (PDA@TCNCs). Step (3): Weigh 0.1g of PDA@TCNCs and dissolve it in 9.0mL of deionized water. Stir overnight and sonicate for 30min to prepare a uniform PDA@TCNCs suspension. Step (4): Subsequently, 8 mL of phytic acid and 2.62 g of polyvinyl alcohol were added to the suspension described in step (2), and the mixture was heated in a 95°C water bath for 2 h to obtain mixture A; Step (5): Dissolve 1g of sodium β-glycerophosphate in 2 mL of deionized water and add it to mixture A. Then heat at 95℃ for 30 min to obtain the mixed precursor solution. Step (7): Pour the degassed solution into a cylindrical or dumbbell-shaped PTFE mold. Place the mold in an ultra-low temperature freezer at -80°C for 10 hours, then remove it and thaw at room temperature (approximately 25°C) for 4 hours. Repeat this freeze-thaw cycle 3 times.

[0044] Step (9); After the final thawing, a tough, transparent hydrogel is obtained. Remove it from the mold and cut it into 40mm×20mm×2mm sheets to obtain a multifunctional polyvinyl alcohol-based hydrogel with photothermal properties, anti-swelling properties, and high conductivity.

[0045] Examples 2-9 Based on the scheme of Example 1, different samples were prepared by adjusting the amount of raw materials, as shown in Table 1.

[0046] Table 1

[0047] To further verify the superior effects of the present invention, the inventors also conducted the following tests on the hydrogels prepared in the embodiments of the present invention (the hydrogels prepared in Examples 1-9 are referred to as Samples 1-9 respectively): Experimental Example 1 Microscopic morphology characterization of polydopamine-encapsulated sea squirt nanocellulose suspension: as shown in the attached figure. Figure 2 As shown, the polydopamine-encapsulated sea squirt cellulose nanoparticles exhibit a regular rod-like structure with significantly increased surface roughness and uniform coating distribution. Measurements show that the PDA@TCNCs have a diameter of approximately 150 nm, a length of 10.5 μm, and an aspect ratio of approximately 70.

[0048] Experimental Example 2 Infrared spectral analysis of the hydrogel: Infrared spectral analysis was performed on the reactants and the hydrogel of Example 1, as shown in the attached figure. Figure 3 As shown in the figure. The spectral data, as indicated by the icons, include the infrared (FT-IR) spectra of the hydrogel, GP, PDA@TCNCs, and PVA. In the infrared spectrum of PVA, at 3430 cm⁻¹...- The broad peak at ¹ is attributed to the OH stretching vibration, 1090 cm⁻¹ - The absorption peak at ¹ is attributed to the CO stretching vibration; in the GP spectrum, the peak at 1718 cm⁻¹ is... - The absorption peak at ¹ is attributed to the P=O stretching vibration, 1080 cm⁻¹ - ¹ and 980 cm - The absorption peak at ¹ is attributed to the stretching vibrations of PO and POH; in the spectrum of PDA@TCNCs, the peak at 1630 cm⁻¹ is... - The absorption peak at ¹ is attributed to the C=C stretching vibration of the aromatic ring in the PDA, 1430 cm⁻¹ - The absorption peak at ¹ is attributed to the bending vibration of phenolic OH groups, 1060 cm⁻¹ - The absorption peak at ¹ is attributed to the COC stretching vibration of the cellulose skeleton. Comparing the infrared spectra of the hydrogel with those of the various raw materials, the hydrogel shows an absorption peak at 960 cm⁻¹. - A new absorption peak appears at position ¹, which is attributed to PO4 in PA. 3- The stretching vibrations of the PO group confirmed the successful introduction of PA into the hydrogel network 3; simultaneously, the hydrogel retained GP at 1718 cm⁻¹. - The characteristic absorption peak at P=O at ¹, and the PDA@TCNCs at 1630 cm⁻¹ - ¹ and 1430 cm - ¹ The characteristic absorption peak of PDA at 1060 cm⁻¹ and at 1060 cm⁻¹ - The characteristic absorption peak at ¹ indicates that both GP and PDA@TCNCs were successfully incorporated into the hydrogel. Notably, the peak is observed in the hydroxyl stretching vibration region (3000-3500 cm⁻¹). - ¹), the OH absorption peak of the hydrogel changed from 3430 cm⁻¹ in pure PVA. - ¹Redshifted to 3420 cm - ¹, and the peak width is significantly narrower and the intensity decreases, indicating that stronger intermolecular hydrogen bond interactions have formed between the hydroxyl groups on the PVA molecular chain and the phosphate hydroxyl groups of GP, the phosphate groups of PA, and the phenolic hydroxyl and amino groups of PDA@TCNCs, restricting the free vibration of the hydroxyl groups. In summary, infrared spectroscopy analysis confirms that all components of PVA, GP, PA, and PDA@TCNCs have been successfully incorporated into the hydrogel network. FT-IR spectroscopy shows the hydroxyl peak of PVA (3430 cm⁻¹). - ¹) The peak intensity decreased after forming hydrogen bonds with PA, GP, and PDA@TCNCs, indicating that many strong hydrogen bonds were formed in the hydrogel.

[0049] Experimental Example 3 Photothermal performance analysis of hydrogels: The hydrogel from Example 1 was selected and placed at room temperature. An 808nm near-infrared laser (power density 1.0 W·cm²) was used to analyze its photothermal properties.- ²) Irradiation, as shown in the attached image Figure 4 As shown, the photothermal properties of the hydrogel increase with increasing irradiation time and tend to stabilize, indicating that the hydrogel has excellent photothermal properties.

[0050] Test Example 4 Analysis of the anti-swelling properties of hydrogels: as shown in the attached figure. Figure 5 As shown, the equilibrium swelling of the hydrogel prepared in Example 1 remained stable, at -18.2% and -12.65%, indicating that the hydrogel has excellent anti-swelling properties.

[0051] Experimental Example 5 Tensile property analysis of hydrogels: The hydrogels described in Examples 1 and 2 to 5 were subjected to compression tests on a universal testing machine, as shown in the attached figures. Figure 6 As shown, the hydrogel exhibits strong mechanical properties.

[0052] Experimental Example 6 Analysis of the high conductivity of the hydrogels: The resistance of the hydrogels described in Examples 1 and 6 to 9 was measured at room temperature using a digital bridge. (See attached...) Figure 7 As shown, the hydrogel has low resistance and high conductivity.

[0053] Experimental Example 7 Analysis of the antibacterial properties of the hydrogel: 2.0 g of polyvinyl alcohol-based hydrogel prepared in Example 1 was sterilized with a UV lamp for 15 min, and then immersed in 0.1 mL of a solution with a concentration of 1.0 × 10⁻⁶ g / mL. 8 The bacteria were co-incubated in a suspension of Staphylococcus aureus and Escherichia coli at CFU / mL at 37 °C for 4 h.

[0054] The samples were divided into two groups: one group received no treatment, and the other group was treated with 808 nm and 1 W / cm². 2 Irradiate with near-infrared light (NIR) for 5 min. Add 100 μL of bacterial suspension (in PBS, 10 μL of PBS) to 1.0 mL PBS. 8 (CFU / mL) to obtain a homogeneous solution, which served as the control group. The control group samples were not subjected to near-infrared laser irradiation treatment. 100 μL of bacterial solution from each group was evenly spread onto agar plates and incubated at 37 ℃ for 12 hours. Colonies on the agar plates were photographed, and colony counting was performed using a J3 colony counter. (See attached image) Figure 8 As shown, it significantly inhibited and disrupted the morphology of bacteria.

[0055] Experimental Example 8 Cytotoxicity analysis of the hydrogel: 2.0 g of polyvinyl alcohol-based hydrogel described in Example 1 was sterilized under UV light for 15 min, then immersed in DMEM liquid culture medium for 48 h to obtain a hydrogel extract. 3T3 cells were cultured in the extract, and cell viability was detected using the MTT assay. (See attached...) Figure 9 As shown, - The cell viability of 3T3 cells cultured in the hydrogel extract reached over 90%, indicating that the hydrogel has low cytotoxicity and good biocompatibility.

[0056] The above description of the disclosed 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 multifunctional polyvinyl alcohol-based hydrogel, characterized in that, The hydrogel uses polyvinyl alcohol (PVA) as the matrix material and polydopamine-encapsulated sea squirt nanocellulose (PDA@TCNCs), sodium β-glycerophosphate (GP), and phytic acid (PA) as functional components. The mass-volume ratio of PVA, PDA@TCNCs, GP, and PA aqueous solutions is 2.62 g: 0.05 g~0.25 g: 1.0 g: 4 mL~12 mL. The mass concentration of the PA aqueous solution is 50%.

2. The multifunctional polyvinyl alcohol-based hydrogel according to claim 1, characterized in that, The polyvinyl alcohol has the structure shown in general formula 1: General Formula 1 In the formula, n is 1700; and the degree of alcoholysis of the polyvinyl alcohol is >98%.

3. A multifunctional polyvinyl alcohol-based hydrogel according to claim 1 or 2, characterized in that, The mass-to-volume ratio of PVA, PDA@TCNCs, GP, and PA aqueous solutions is 2.62 g: 0.1 g: 1.0 g: 8 mL.

4. A method for preparing a multifunctional polyvinyl alcohol-based hydrogel according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Dissolve PDA@TCNCs in deionized water, stir overnight and sonicate to obtain PDA@TCNCs suspension; (2) Add PA aqueous solution and PVA sequentially to the PDA@TCNCs suspension in step (1), and heat in a water bath to obtain mixture A; (3) Dissolve GP in deionized water, add it to the mixture A described in step (2) after dissolution, and heat it in a water bath to obtain the mixed precursor solution; (4) After degassing the mixed precursor liquid, inject it into the mold, freeze it at -80℃ for 8-12 hours, and then thaw it at room temperature for 3-6 hours; (5) Repeat the freezing-thawing process 2-4 times to obtain the multifunctional polyvinyl alcohol-based hydrogel.

5. The method for preparing a multifunctional polyvinyl alcohol-based hydrogel according to claim 4, characterized in that, In step (1), the mass-to-volume ratio of PDA@TCNCs to deionized water is (0.05~0.25) g: (5~12) mL.

6. The method for preparing a multifunctional polyvinyl alcohol-based hydrogel according to claim 4, characterized in that, The preparation method of PDA@TCNCs is as follows: thiamin is isolated from true sea squirts and hydrolyzed with sulfuric acid. After standing, it is centrifuged and then dialyzed with deionized water until neutral. Then, it is concentrated by vacuum rotary evaporation to obtain a uniform sea squirt nanocellulose suspension with a concentration of 1.0 wt%. The TCNCs suspension is dispersed in Tris buffer, dopamine hydrochloride is added, and oxidative polymerization is carried out at pH = 8.5 for 12-24 hours. After centrifugation and washing, polydopamine-coated sea squirt nanocellulose PDA@TCNCs are obtained.

7. The method for preparing a multifunctional polyvinyl alcohol-based hydrogel according to claim 4, characterized in that, Step (2) The water bath heating temperature is 95℃ and the time is 2 hours.

8. The method for preparing a multifunctional polyvinyl alcohol-based hydrogel according to claim 4, characterized in that, Step (3) The mass-to-volume ratio of GP to deionized water is 1g:2mL; the water bath heating temperature is 95℃ and the time is 30 min.

9. The application of the hydrogel as described in claims 1 to 3 or the hydrogel prepared by the preparation method according to any one of claims 4 to 8 in the field of sensing.

10. The application as described in claim 9, characterized in that, Applications of the hydrogel in wearable strain sensors, underwater motion monitoring sensors, and triboelectric nanogenerators.

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