Self-healing pressure sensitive material based on solvent displacement and preparation method and application thereof

Abstract

The application relates to the technical field of pressure-sensitive materials, and provides a self-repairing pressure-sensitive material based on solvent replacement and a preparation method and application thereof, the pressure-sensitive material comprising a hydrogel; the hydrogel comprises polyvinylpyrrolidone and gallic acid; a dynamic hydrogen bond network is formed between amide carbonyl in a molecular chain backbone of at least part of the polyvinylpyrrolidone and hydroxyl of at least part of the gallic acid; the dynamic hydrogen bond network changes a fluid structure of the hydrogel with strain change; and intermolecular pi-pi stacking structures are formed between at least part of the gallic acid molecules. The preparation method is a solvent replacement method for preparing the hydrogel, and the application has obvious advantages in aspects of preparation process simplicity, bacteriostatic safety, pressure-sensitive performance and durability, and can effectively solve problems of poor mechanical matching, unstable interface and easy damage of existing hydrogel pressure sensors, and has outstanding technical effects.

Description

Technical Field

[0001] This invention relates to the field of pressure-sensitive materials technology, and in particular to a self-healing pressure-sensitive material based on solvent displacement, its preparation method, and its application. Background Technology

[0002] With the rapid development of flexible technology, flexible pressure sensors have attracted significant attention in wearable biomedical electronic devices, human-machine interfaces, human motion monitoring, and physiological health detection. Based on their sensing mechanisms, flexible pressure sensors are mainly classified into piezoresistive, capacitive, and piezoelectric types. Among them, piezoresistive pressure sensors have achieved great success due to their advantages such as simple structure, high sensitivity, fast response speed, wide dynamic range, and low manufacturing cost. The pressure-sensitive material, as the core functional layer, is embedded between two electrodes. Based on its unique resistance-pressure response characteristics, it accurately converts external mechanical pressure into a resistance signal output, driving the device to achieve pressure sensing functionality.

[0003] Hydrogels, as pressure-sensitive materials, possess several technological advantages. However, when traditional hydrogels are used in pressure sensors, conductive fillers are typically added to achieve pressure-sensitive conductivity. This method often significantly compromises the intrinsic mechanical properties of the hydrogel, such as a marked decrease in elongation at break and a significant increase in Young's modulus, leading to mechanical mismatch with biological tissues. Furthermore, when hydrogels fracture due to external overload or when the cross-linked network breaks and accumulates, forming internal microcracks, their structure cannot self-repair, severely impacting their lifespan. These factors significantly limit the application range of hydrogel-based pressure-sensitive materials in pressure sensors. Summary of the Invention

[0004] To at least partially solve the above-mentioned technical problems, the present invention provides a self-healing pressure-sensitive material based on solvent displacement, its preparation method and application.

[0005] Specifically, the present invention provides a pressure-sensitive material, including a hydrogel; The hydrogel comprises polyvinylpyrrolidone and gallic acid; A dynamic hydrogen bond network is formed between the amide carbonyl group in the main chain of at least a portion of the polyvinylpyrrolidone and the hydroxyl group in at least a portion of the gallic acid, and the dynamic hydrogen bond network causes the hydrogel to produce a continuous change in resistance under the action of external force. At least some of the gallic acid molecules form a π-π stacked structure, which enhances the electronic conductivity of the pressure-sensitive material.

[0006] The hydrogel system of this invention comprises two parts: polyvinylpyrrolidone (PVP) and gallic acid (GA). PVP, as a hydrophilic component, possesses tunable mechanical properties and promotes strain recovery. Its amide carbonyl group (C=O) in the main chain provides abundant hydrogen bond acceptor sites, which can form a dynamic hydrogen bond network with the hydroxyl groups of GA. This dynamic hydrogen bond network endows the hydrogel's internal structure with reversible reconstruction capabilities, allowing the hydrogel to undergo continuous structural evolution under external forces, thereby generating continuously tunable resistance changes and achieving reversible cross-linking and self-healing properties. The GA molecule simultaneously performs two functions: its aromatic ring planar structure can form π-π stacks to enhance electronic conductivity, and its polyhydroxy structure can promote hydrophobic associations in the hydrogel precursor during solvent replacement, thus constructing a multi-level, non-covalently driven microstructure. Specifically, hydrophobic associations are the inducing factor for phase separation, causing the system of this invention to induce a non-equilibrium biphase structure during solvent replacement gelation, composed of a polymer-enriched supporting phase and a solvent-rich dynamic phase. This phase-separated structure dominates the mechanical and dynamic behavior of the hydrogel. The polymer-enriched supporting phase provides modulus and strength, while the solvent-rich dynamic phase endows the system with large deformation capacity, energy dissipation, and rapid network reconstruction characteristics. In this invention, the network structure and mechanical behavior of the hydrogel can be controlled by altering the competitive relationships among hydrogen bonds, π-π stacking, and hydrophobic interactions.

[0007] The hydrogel of this invention possesses rapid self-healing properties due to the presence of numerous reversible dynamic hydrogen bonds, hydrophobic interactions, and weak π-π stacking non-covalent interactions within it. When the hydrogel is damaged by external forces, causing network breakage, its internal chain segments can automatically reconstruct at room temperature. The storage modulus can recover to more than 98% of its initial value within a short time after switching between high and low strain. Cut-heal experiments also demonstrate that the fractured interface of the hydrogel can self-heal and restore its overall structure without heating or light exposure. This self-healing property significantly extends the service life of the hydrogel material in flexible electronic devices and avoids the degradation of electrical performance caused by the accumulation of microcracks, an advantage that traditional non-repairable hydrogels lack.

[0008] Meanwhile, this invention uses naturally derived small-molecule polyphenol gallic acid (GA) as a functional component, making the material system safe, green, and free of metal ion residue risks. GA participates in hydrogen bond construction within the hydrogel network and can also form a stable antibacterial microenvironment on the material surface in a sustained-release manner, thus exhibiting a long-lasting and significant inhibitory effect on common pathogenic bacteria such as Staphylococcus aureus and Escherichia coli. The antibacterial rate remains high in multiple rounds of experiments. Compared with traditional methods that rely on silver ions or nano-metal oxides for antibacterial effects, the material of this invention has higher biocompatibility and greater safety advantages for medical devices and flexible electronics.

[0009] According to the pressure-sensitive material provided by the present invention, the mass ratio of the polyvinylpyrrolidone and the gallic acid is (0.5~2):1, preferably 1:1.

[0010] The molecular weight of the polymer affects the continuity and network stability of the polymer-enriched phase during solvent displacement-induced phase separation by influencing the segment length and entanglement density, thus significantly affecting the mechanical properties, pressure-sensitive response, and self-healing behavior of the pressure-sensitive hydrogel of this invention. Higher molecular weight PVP can form a continuous and stable support framework without covalent crosslinking, enabling the gel to undergo reversible deformation and generate a stable and repeatable pressure-sensitive signal during compression; while lower molecular weight PVP results in insufficient continuity of the polymer-enriched support phase, easily leading to structural collapse and signal instability. Therefore, this invention preferably uses high molecular weight PVP to achieve a pressure-sensitive hydrogel with optimal overall performance. Preferably, in the pressure-sensitive material provided by this invention, the molecular weight M of the polyvinylpyrrolidone is... w The value is between 1 million and 1.5 million, with 1.3 million being the preferred value.

[0011] According to the pressure-sensitive material provided by the present invention, the highest yield stress of the hydrogel is 3~7 kPa, for example, it can be any value or a range of values ​​composed of 3 kPa, 4 kPa, 5 kPa, 6 kPa, and 7 kPa; and / or, The fluid structure of the hydrogel changes with strain, including: at a first strain, the storage modulus of the hydrogel is higher than its loss modulus; at a second strain, the hydrogel is in a fluid state; the first strain is less than the second strain; preferably, at a first strain of 1%, the storage modulus of the hydrogel is higher than its loss modulus; and at a second strain of 800%, the hydrogel is in a fluid state; and / or, The maximum fracture strain of the hydrogel is 800%~1800%, for example, it can be any value or a range of values ​​from 800%, 900%, 1000%, 1100%, 1200%, 1300%, 1400%, 1500%, 1600%, 1700%, 1800%; and / or, The maximum tensile strength of the hydrogel is 90~150 kPa, for example, it can be any value or a range of values ​​among 90 kPa, 100 kPa, 110 kPa, 120 kPa, 130 kPa, 140 kPa, and 150 kPa; and / or, The hydrogel has a Young's modulus of 1 to 40 kPa, for example, it can be any value or a range of values ​​among 1 kPa, 10 kPa, 20 kPa, 30 kPa, and 40 kPa.

[0012] According to the pressure-sensitive material provided by the present invention, the hydrogel is prepared by solvent displacement method; the solvent displacement method includes placing the hydrogel precursor solution in water for solvent displacement; the solvent of the hydrogel precursor solution is an aqueous ethanol solution; preferably, the volume concentration of ethanol in the aqueous ethanol solution is 55~75%, for example, it can be any value or a numerical range composed of any values ​​among 55%, 60%, 65%, 70%, and 75%.

[0013] This invention achieves gel formation by solvent displacement of the hydrogel precursor solution. PVP and GA form a dynamic hydrogen bond network, and the polyhydroxy structure of GA molecules further promotes hydrophobic interactions in the hydrogel precursor during solvent displacement, thereby constructing a multi-level, non-covalently driven microstructure. By controlling the proportion of ethanol in the solvent system, the solvent displacement rate can be effectively adjusted, and the competitive relationship between hydrogen bonds, π-π stacking, and hydrophobic interactions can be altered, thus achieving control over the hydrogel network structure and mechanical behavior.

[0014] The hydrogel proposed in this invention is prepared using a solvent displacement method. Gel formation is achieved simply by placing the PVP-GA precursor solution in a mold and immersing it in deionized water, eliminating the need for additional chemical crosslinking agents, photocuring conditions, or repeated drying-swelling steps. This method is adaptable to molds of different shapes, making the hydrogel molding process highly controllable. It also avoids the structural inhomogeneity, deformation, and defect accumulation caused by multiple steps in traditional preparation processes, thereby significantly improving the consistency and yield of the finished product and greatly reducing preparation complexity and engineering costs, demonstrating excellent potential for large-scale production.

[0015] According to the pressure-sensitive material provided by the present invention, the hydrogel precursor solution comprises the polyvinylpyrrolidone, the gallic acid and an aqueous ethanol solution; Preferably, the mass concentration of polyvinylpyrrolidone in the hydrogel precursor solution is 2.5% or more, and more preferably 2.5-5%.

[0016] According to the pressure-sensitive material provided by the present invention, the hydrogel precursor solution is obtained by mixing a PVP solution and a GA solution, wherein the PVP solution is obtained by mixing PVP and an aqueous ethanol solution, and the GA solution is obtained by mixing GA and an aqueous ethanol solution.

[0017] The present invention also provides a method for preparing the pressure-sensitive material as described above, including preparing the hydrogel by solvent displacement method.

[0018] The present invention also provides a pressure sensor, comprising the pressure-sensitive material as described above, or the pressure-sensitive material prepared by the preparation method described above; Preferably, the pressure sensor exhibits a two-stage response in the sensitivity range of 0~15kPa; More preferably, the two-stage response includes a sensitivity of 0.2~0.3kPa within the range of 0~1.37kPa. -1 The sensitivity within the 1.37~15kPa range is 0.06~0.07kPa. -1 .

[0019] The pressure-sensitive material prepared by this invention exhibits excellent piezoresistive properties without the addition of conductive fillers. Its dynamic hydrogen bond network can generate stable and continuous resistance changes under external force. This hydrogel has a stable operating range in the range of 0~15kPa, and its sensitivity range can meet the needs of different applications such as weak tactile detection and monitoring of large biomechanical signals. The signal output is stable and has good repeatability, which is superior to the problems of unstable conductive paths and filler aggregation faced by conventional filler-reinforced hydrogels.

[0020] The present invention also provides a flexible sensor, comprising the pressure-sensitive material as described above, or the pressure-sensitive material prepared by the preparation method described above, or the pressure sensor as described above.

[0021] The present invention provides a solvent-displacement-based self-healing pressure-sensitive material, its preparation method, and its application. By constructing a hydrogel system in which a dynamic hydrogen bond network is formed between the amide carbonyl groups in the molecular backbone of at least a portion of the polyvinylpyrrolidone and the hydroxyl groups of at least a portion of the gallic acid, the hydrogel system also contains a π-π stacked structure formed between at least a portion of the gallic acid molecules. It possesses rapid self-healing properties and excellent mechanical properties, and exhibits excellent piezoresistive characteristics without relying on conductive fillers.

[0022] This invention has significant advantages in terms of simple preparation process, antibacterial safety, pressure sensitivity and durability. It can effectively solve the problems of poor mechanical matching, unstable interface and easy damage in existing hydrogel pressure sensors, and the technical effect is outstanding. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the preparation process of the pressure-sensitive material provided by the present invention.

[0025] Figure 2 This is a schematic diagram illustrating the preparation principle of the pressure-sensitive material provided by the present invention.

[0026] Figure 3This is a test result diagram of Test Example 1 provided by the present invention.

[0027] Figure 4 This is a test result diagram of Test Example 2 provided by the present invention.

[0028] Figure 5 This is a test result diagram of Test Example 3 provided by the present invention.

[0029] Figure 6 This is a test result diagram of Test Example 4 provided by the present invention.

[0030] Figure 7 This is a test result diagram of Test Example 5 provided by the present invention.

[0031] Figure 8 This is a test result diagram of Test Example 6 provided by the present invention.

[0032] Figure 9 This is a test result diagram of Test Example 7 provided by the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels. Polyvinylpyrrolidone (PVP, Mw=1300000), polyvinylpyrrolidone (PVP, Mw=40000), and gallic acid (GA) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (Shanghai, China). Anhydrous ethanol was purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). All reagents have undergone high-purity finished product processing and do not require further purification.

[0035] Unless otherwise specified, all experiments in this invention are conducted at room temperature and pressure. Generally, room temperature refers to 20~40℃ and atmospheric pressure refers to 1 atmosphere.

[0036] Example 1 This embodiment provides a method for preparing a pressure-sensitive material, such as... Figure 1 As shown, the steps are as follows: (1) Preparation of solution Polyvinylpyrrolidone (PVP, Mw=1300000) and an aqueous ethanol solution (ethanol volume concentration of 55%) were mixed and stirred at room temperature for 4 hours to obtain a PVP solution; wherein the mass concentration of PVP in the PVP solution was 10%.

[0037] GA and an aqueous ethanol solution (ethanol volume concentration of 55%) were mixed and stirred at 80°C until completely dissolved to obtain a GA solution; wherein the mass concentration of GA in the GA solution was 10%.

[0038] (2) Mix the PVP solution and GA solution prepared in step (1) and stir for 2 hours to obtain a mixed solution. The mass ratio of PVP to GA in the mixed solution is 1:1, and the mass concentration of PVP is 5%.

[0039] (3) Add the mixed solution obtained in step (2) into the mold, and then soak it in water for 24 hours to obtain the hydrogel, i.e., the pressure-sensitive material. The formation principle of the hydrogel is shown in the figure below. Figure 2 As shown.

[0040] Example 2 It is basically the same as Example 1, except that the volume concentration of ethanol in the aqueous ethanol solution is adjusted to 65%.

[0041] Example 3 It is basically the same as Example 1, except that the volume concentration of ethanol in the aqueous ethanol solution is adjusted to 75%.

[0042] Test Example 1: Fourier Transform Infrared Spectroscopy Test Fourier transform infrared spectroscopy was performed on PVP, GA, and pressure-sensitive materials. The test results are as follows: Figure 3 As shown. The pressure-sensitive material in Example 1 is denoted as PG. 55% The pressure-sensitive material in Example 2 is designated as PG. 65% The pressure-sensitive material in Example 3 is designated as PG. 75% .

[0043] from Figure 3 It can be seen from this: Pure PvP at 1671 cm -1 and 1227 cm -1 These correspond to the characteristic peaks of C=O and CN, respectively. Pure GA has a peak at 1632 cm⁻¹. -1 The C=O characteristic peak is present. After hydrogel molding, the C=O and CN characteristic peaks in the spectrum of the pressure-sensitive material show varying degrees of red shift.

[0044] Meanwhile, GA is at 3495 cm. -1 and 3282 cm -1It exhibits a typical -OH vibration peak at 3000-3500 cm⁻¹ after gelation. -1 The absorption peak intensity decreased significantly, and the -OH vibration peak shifted to a lower wavenumber, indicating that -OH participated in the formation of a large number of hydrogen bonds.

[0045] These changes all indicate that intermolecular hydrogen bonds have formed between PVP and GA.

[0046] Test Example 2: X-ray Diffraction (XRD) Experiment X-ray diffraction (XRD) experiments were performed on PVP, GA, and pressure-sensitive materials. The test results are as follows: Figure 4 As shown. The pressure-sensitive material in Example 1 is denoted as PG. 55% The pressure-sensitive material in Example 2 is designated as PG. 65% The pressure-sensitive material in Example 3 is designated as PG. 75% .

[0047] from Figure 4 It can be seen from this: The presence of π-π stacking interactions in the pressure-sensitive material. Specifically, as shown in the figure, the apparent peak at d=3.53Å represents the typical distance of π-π stacking interactions. The intensity of the diffraction peaks related to aromatic stacking in the pressure-sensitive material decreases and broadens with increasing ethanol volume ratio in the mixed solution, indicating that during solvent displacement, hydrogen bonds / interactions between PVP and GA gradually replace the planar π-π stacking of GA, leading to a decrease in system order and a tendency towards amorphization.

[0048] Test Example 3: Rheological Test Based on structural characterization, to reveal the influence of non-covalent regulation on macroscopic mechanical behavior, this invention conducted systematic rheological tests on pressure-sensitive materials obtained by solvent replacement with different ethanol volume ratios, in order to explore the structural mechanism and screen the optimal material system suitable as a degradable piezoresistive sensing unit. The pressure-sensitive material in Example 1 is denoted as PG. 55% The pressure-sensitive material in Example 2 is designated as PG. 65% The pressure-sensitive material in Example 3 is designated as PG. 75% .

[0049] An amplitude scanning experiment with a constant frequency of 5 Hz was performed, as follows: Figure 5 As shown in (a), the storage modulus (G') experimentally determined in all hydrogel formulations was significantly higher than the loss modulus (G'') in the initial stress range, confirming the elastic-dominant nature of the hydrogel. As shear stress increased, the two moduli operated in parallel, maintaining almost constant values ​​until a specific stress threshold (i.e., yield stress) was reached, at which point the storage modulus value suddenly decreased due to enhanced energy dissipation caused by hydrogen bond breaking.

[0050] like Figure 5As shown in (b), the yield stress of the hydrogel decreases with increasing ethanol volume ratio in the mixed solution. The highest yield stress observed in the pressure-sensitive material obtained in Example 1 was 6.6 kPa, while the yield stress decreased sequentially in the Example 2 (4.5 kPa) and Example 3 (3.7 kPa) groups. This phenomenon confirms the chemical characterization results and is attributed to the competitive effect of multiple interactions in the gel network. Hydrogen bonds are highly dynamic and reversible interactions, and their rapid exchange makes molecular chain segments easier to slip and rearrange, thereby lowering the yield point. In addition, the increased ethanol volume ratio in the mixed solution leads to a significant weakening of π-π stacking, increasing the overall flexibility of the network. Therefore, with increasing ethanol volume ratio in the mixed solution, the hydrogel macroscopically enters a flow state more easily, resulting in a decrease in yield stress.

[0051] Test Example 4: High and Low Strain Cyclic Test To evaluate the structural reconstruction capability of hydrogels after external damage, high and low strain cycle tests were conducted on hydrogels with different solvents, such as... Figure 6 As shown in (a). The pressure-sensitive material of Example 1 is denoted as PG. 55% The pressure-sensitive material in Example 2 is designated as PG. 65% The pressure-sensitive material in Example 3 is designated as PG. 75% .

[0052] Under low strain (1%) conditions, the storage modulus of Examples 1-3 was significantly higher than the loss modulus, exhibiting a stable elastic network structure. When the strain instantaneously switched to high strain (800%), it dropped sharply by several orders of magnitude and fell below, indicating that the hydrogel network was rapidly destroyed and transformed into a fluidized state. After returning to low strain, all three hydrogels could recover to more than 98% of their initial value within 2 seconds, indicating that the dynamic hydrogen bonds between hydroxyl and carbonyl groups in the hydrogel network played an important role in improving the self-healing ability of the synthesized hydrogels and could rapidly rebuild the network. Meanwhile, for PG... 55% Cut-heal tests were conducted to observe the self-healing properties of the material. Figure 6 (b)).

[0053] Test Example 5 Mechanical Property Test To systematically evaluate the macroscopic mechanical behavior of the pressure-sensitive materials obtained in Examples 1-3, the present invention further conducted uniaxial tensile stress-strain tests on the samples, and the results are as follows: Figure 7 As shown in (a), all three groups of pressure-sensitive materials exhibited high tensile deformation capacity, but their mechanical behavior showed significant differences with the change in the volume ratio of ethanol in the mixed solution, such as... Figure 7 As shown in (b). The pressure-sensitive material of Example 1 is denoted as PG. 55% The pressure-sensitive material in Example 2 is designated as PG. 65% The pressure-sensitive material in Example 3 is designated as PG. 75% .

[0054] Specifically, the pressure-sensitive material of Example 1 exhibited the best ductility, with a maximum fracture strain (1738.59±55.22%), displaying typical characteristics of a soft tissue with low modulus and high elongation. The increased number of hydrogen bonds and decreased chain segment mobility within the hydrogel network led to a decreasing trend in fracture strain: the fracture strains of the pressure-sensitive materials of Examples 2 and 3 gradually decreased, to 1303.53±42.35% and 835.16±55.56%, respectively.

[0055] The maximum tensile strength increases with the increase of the volume ratio of ethanol in the mixed solution. The pressure-sensitive material of Example 1 exhibits the maximum tensile strength of 90.09 ± 7.89 kPa, while the maximum tensile strength of the pressure-sensitive materials of Examples 2 and 3 gradually decreases to 113.06 ± 7.88 kPa and 139.41 ± 9.38 kPa, respectively.

[0056] This trend indicates that as the proportion of ethanol increases, the overall material network becomes denser and more rigid, thereby improving tensile strength.

[0057] Further calculation of Young's modulus can intuitively reflect the structure-property relationship of the material under different solvent systems. The results show that with increasing ethanol content, the hydrogel exhibits a trend of mechanical properties changing from soft and stretchy to stiff and enhanced. As shown in 7(c), the Young's modulus of the pressure-sensitive material in Example 3 is significantly higher than that in Examples 2 and 1, at 37.02±3.62 kPa, 12.85±3.00 kPa, and 5.95±2.12 kPa, respectively. It is worth emphasizing that Example 1 (PVP–GA) 55% The Young's modulus of hydrogels is close to, and even lower than, that of brain tissue (such as the cerebral cortex, which is about 1 to 40 kPa). This can reduce inflammatory responses and give them potential advantages in terms of flexibility and biointerface compatibility, which is conducive to realizing implantable flexible sensing applications with low modulus and low mechanical disturbance.

[0058] Test Example 6 Antibacterial Performance The pressure-sensitive material constructed in this invention also possesses significant antibacterial properties. Because gallic acid containing a polyphenolic hydroxyl structure is introduced into the hydrogel system, it can achieve bactericidal effects by disrupting the bacterial cell wall structure and inhibiting cell metabolism and redox processes.

[0059] This test case selected Staphylococcus aureus and Escherichia coli as typical Gram-positive and Gram-negative bacteria, respectively, for antibacterial evaluation. The results are as follows: Figure 8As shown, compared with the control group, the optical density of the bacterial culture system treated with hydrogel decreased significantly, indicating that the hydrogel material can effectively inhibit bacterial growth. Specifically, the OD600 values ​​of the S. aureus and E. coli control groups were 0.88583±0.00496 and 1.1175±0.01956, respectively, while the corresponding values ​​after treatment with the hydrogel material (pressure-sensitive material prepared in Example 1) decreased to 0.36872±0.01717 and 0.17623±0.00482, respectively, with reductions exceeding 50% and 80%, showing a significant difference (p<0.001). This result indicates that the pressure-sensitive material of the present invention has a strong antibacterial effect against both Gram-positive and Gram-negative bacteria.

[0060] Test Example 7: Pressure Sensitive Performance The pressure-sensitive material (2cm × 2cm × 0.5mm) prepared in Example 1 was assembled into a sandwich-structured pressure sensor, and then further assembled into a flexible sandwich-structured pressure sensor. The device was then fixed on an electronic universal testing machine and subjected to loading tests within a pressure range of 0–15 kPa, while its resistance changes were recorded in real time to calculate the sensitivity. The results are as follows: Figure 9 As shown, the sensor has a stable operating range in the 0~15kPa range, and its sensitivity exhibits a two-segment characteristic, with the sensitivity at 0.218kPa. -1 (0~1.37kPa) and 0.057kPa -1 (1.37~15kPa).

[0061] Examples 4-8 The results are basically the same as in Example 1, except for the mass ratio of PVP and GA in the mixed solution and the mass concentration of PVP, as shown in Table 1.

[0062] Comparing the performance of the pressure-sensitive materials prepared in Examples 4-8 with that in Example 1, it was found that rheological amplitude scanning experiments were conducted on hydrogels with different concentrations or ratios of PVP and GA to obtain the yield strength of hydrogels with different concentration ratios. This yield strength can be used to evaluate the ratio of network strength to damage resistance. The specific test results are shown in Table 1 below.

[0063] Table 1

[0064] The data above shows that a hydrogel with a complete structure and high yield strength can be formed when both PVP and GA concentrations are 5%. When the GA content is reduced to 2.5% or 0.5%, although gelation can still occur in the 5%:2.5% system, the yield strength decreases significantly; while the 5%:0.5% formulation cannot gel at all, indicating that the GA concentration is insufficient to support an effective hydrogen bond and π-π stacking network. Further reducing the PVP concentration to 2.5% has a more significant impact on the gelation and mechanical properties of the system. Although the 2.5%:5% sample can gel and exhibits the highest yield strength, it is prone to local aggregation and poor uniformity during solvent displacement; while the 2.5%:2.5% formulation can gel stably, but the yield strength is only 3.88 kPa, indicating insufficient network strength. In addition, the 2.5%:0.5% formulation cannot form a gel structure, further verifying the conclusion that it is difficult to establish an effective dynamic cross-linked network in low-concentration systems. Considering multiple indicators such as gelation properties, structural uniformity, and yield strength, the system in Example 1 was ultimately determined to be the optimal formulation. This formulation combines the advantages of stable gelation, moderate viscosity, good elasticity, and the highest yield strength, providing a robust and reversible kinetic crosslinking network, thus providing a reliable material basis for the subsequent construction of a biodegradable piezoresistive intracranial pressure sensor.

[0065] Comparative Example 1 It is basically the same as Example 1, except that GA and other quantities are replaced with tannic acid.

[0066] The results showed that, in the absence of a sol, the two directly formed a hydrogel when mixed.

[0067] Comparative Example 2 It is basically the same as Example 1, except that the volume concentration of ethanol in the aqueous ethanol solution is adjusted to 50%.

[0068] The results showed that, in the absence of a sol, the two directly formed a hydrogel when mixed.

[0069] Comparative Example 3 It is basically the same as Example 1, except that the volume concentration of ethanol in the aqueous ethanol solution is adjusted to 80%.

[0070] The results showed that, in the absence of a sol, the two directly formed a hydrogel when mixed.

[0071] Comparative Example 4 This is essentially the same as Example 1, except that polyvinylpyrrolidone (PVP, Mw=1300000) was replaced by polyvinylpyrrolidone (PVP, Mw=40000) by mass.

[0072] The results showed that, in the absence of a sol, the two directly formed a hydrogel when mixed.

[0073] As can be seen from the above data, this invention successfully constructs a sol state, enabling the system to be stably placed in a pre-set container for subsequent solvent replacement, thereby inducing the controllable formation of hydrogels. If the reaction system solidifies directly into a hydrogel without going through the sol state, it will not only completely block the subsequent solvent replacement process, but also cause the mixture to gel instantaneously and unevenly during stirring, thus completely losing control over the formation of the hydrogel morphology.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pressure-sensitive material, characterized in that, Including hydrogels; The hydrogel comprises polyvinylpyrrolidone and gallic acid; A dynamic hydrogen bond network is formed between the amide carbonyl group in the main chain of at least a portion of the polyvinylpyrrolidone and the hydroxyl group in at least a portion of the gallic acid, and the dynamic hydrogen bond network causes the hydrogel to produce a continuous change in resistance under the action of external force. At least some of the gallic acid molecules form a π-π stacked structure, which enhances the electronic conductivity of the pressure-sensitive material.

2. The pressure-sensitive material according to claim 1, characterized in that, The mass ratio of the polyvinylpyrrolidone to the gallic acid is (0.5~2):1, preferably 1:

1.

3. The pressure-sensitive material according to claim 1 or 2, characterized in that, The molecular weight M of the polyvinylpyrrolidone w The value is between 1 million and 1.5 million, with 1.3 million being the preferred value.

4. The pressure-sensitive material according to any one of claims 1 to 3, characterized in that, The highest yield stress of the hydrogel is 3~7 kPa; and / or, The fluid structure of the hydrogel changes with strain, including: at a first strain, the storage modulus of the hydrogel is higher than its loss modulus; at a second strain, the hydrogel is in a fluid state; the first strain is less than the second strain; preferably, at a first strain of 1%, the storage modulus of the hydrogel is higher than its loss modulus; and at a second strain of 800%, the hydrogel is in a fluid state; and / or, The maximum fracture strain of the hydrogel is 800%~1800%; and / or, The maximum tensile strength of the hydrogel is 90~150 kPa; and / or, The Young's modulus of the hydrogel is 1~40 kPa.

5. The pressure-sensitive material according to any one of claims 1 to 4, characterized in that, The hydrogel is prepared by solvent displacement method; the solvent displacement method includes placing the hydrogel precursor solution in water for solvent displacement; the solvent of the hydrogel precursor solution is an aqueous ethanol solution; preferably, the volume concentration of ethanol in the aqueous ethanol solution is 55~75%.

6. The pressure-sensitive material according to claim 5, characterized in that, The hydrogel precursor solution comprises the polyvinylpyrrolidone, the gallic acid, and an aqueous ethanol solution; Preferably, the mass concentration of polyvinylpyrrolidone in the hydrogel precursor solution is 2.5% or more, and more preferably 2.5-5%.

7. The pressure-sensitive material according to claim 5 or 6, characterized in that, The hydrogel precursor solution is obtained by mixing a PVP solution and a GA solution. The PVP solution is obtained by mixing PVP and an aqueous ethanol solution, and the GA solution is obtained by mixing GA and an aqueous ethanol solution.

8. A method for preparing the pressure-sensitive material according to any one of claims 1 to 7, characterized in that, This includes preparing the hydrogel using a solvent displacement method.

9. A pressure sensor, characterized in that, Includes the pressure-sensitive material according to any one of claims 1 to 7, or the pressure-sensitive material prepared by the preparation method according to claim 8; Preferably, the pressure sensor exhibits a two-stage response in the sensitivity range of 0~15kPa; More preferably, the two-stage response includes a sensitivity of 0.2~0.3kPa within the range of 0~1.37kPa. -1 The sensitivity within the 1.37~15kPa range is 0.06~0.07kPa. -1 .

10. A flexible sensor, characterized in that, It includes the pressure-sensitive material according to any one of claims 1 to 7, or the pressure-sensitive material prepared by the preparation method according to claim 8, or the pressure sensor according to claim 9.

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