Simple preparation method and application of high-toughness PVA conductive hydrogel

Abstract

The invention relates to the technical field of high polymer material preparation, in particular to a simple preparation method and application of high-toughness PVA conductive hydrogel, and the simple preparation method comprises the following steps: adding polyvinyl alcohol into deionized water, and dissolving under water bath heating to obtain a polyvinyl alcohol aqueous solution; cooling the polyvinyl alcohol aqueous solution to room temperature, pouring the cooled polyvinyl alcohol aqueous solution into a mold, sealing the mold with a preservative film, freezing the mold, and unfreezing the mold to obtain polyvinyl alcohol hydrogel; and soaking the polyvinyl alcohol hydrogel in a 1 mol / L salt solution to obtain the high-toughness PVA conductive hydrogel. The polyvinyl alcohol hydrogel prepared in the invention has ultrahigh strength and toughness and good conductivity, and can be well applied to flexible sensors.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material preparation, and in particular to a simple preparation method and application of a high-strength and tough PVA conductive hydrogel. Background Art

[0002] Hydrogel is a water-absorbing gel-like substance made of polymer materials, mainly composed of cross-linked polymer networks. When exposed to water, these cross-linked polymer networks can absorb and retain large amounts of water, forming a jelly-like gel-like structure.

[0003] The preparation method of polyvinyl alcohol hydrogel prepared with polyvinyl alcohol as raw material is simple, and it has the advantages of flexibility, water-richness and good biocompatibility. It is widely used in industry, agriculture, medicine and other fields, and has broad application prospects in the research of bionic electronic skin, wearable electronic devices and flexible sensors.

[0004] However, like most hydrogels, polyvinyl alcohol hydrogel has inherent disadvantages of poor mechanical strength and easy rupture. Its low strength, toughness, and weak conductivity seriously affect its application in wearable electronic devices and flexible sensors. Therefore, the development of strong and tough conductive hydrogels has become a research hotspot. How to prepare hydrogels with high toughness and good conductivity while maintaining the biocompatibility of hydrogels, non-toxic effects, and green and environmentally friendly has become an important research direction for hydrogels. In view of the problems of poor mechanical properties, low toughness, easy rupture, and low conductivity of polyvinyl alcohol hydrogels, the present invention provides a simple and efficient method for preparing high-toughness PVA conductive hydrogels, and demonstrates the application of such hydrogels. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a preparation method and application of high-toughness PVA conductive hydrogel. First, a polyvinyl alcohol aqueous solution is thawed by low-temperature freezing to form a polyvinyl alcohol hydrogel, and then the polyvinyl alcohol hydrogel is added to various phosphate solutions for immersion to obtain a high-toughness PVA conductive hydrogel. Finally, based on its high strength and good conductivity, it is applied in the field of flexible sensors.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A simple preparation method of high-strength and tough PVA conductive hydrogel comprises the following steps: S1, adding polyvinyl alcohol into deionized water, dissolving it in a water bath, and obtaining a polyvinyl alcohol aqueous solution; S2, cooling the polyvinyl alcohol aqueous solution obtained in step S1 to room temperature, pouring it into a mold, sealing it with a plastic wrap, freezing it in a refrigerator, and then thawing it to obtain a polyvinyl alcohol hydrogel; S3. Soaking the polyvinyl alcohol hydrogel obtained in step S2 in a 1 mol / L salt solution to obtain a high-strength and tough PVA conductive hydrogel.

[0007] Furthermore, the water bath temperature in S1 is 95° C., and the concentration of the final polyvinyl alcohol aqueous solution is 10 wt %.

[0008] Furthermore, the freezing temperature in S2 is -20°C and the freezing time is 12 hours.

[0009] Furthermore, the concentration of the salt solution in S3 is 1 mol / L.

[0010] Furthermore, the salt solution is one of sodium dihydrogen phosphate, disodium hydrogen phosphate, and sodium phosphate.

[0011] Furthermore, the soaking time in S3 is 12-60 hours.

[0012] The present invention also provides application of the PVA conductive hydrogel in the field of flexible sensors.

[0013] The beneficial effects of the present invention are: The present invention uses polyvinyl alcohol as a raw material, which has good biocompatibility and biodegradability and can be applied in a wider range. The method used to prepare the hydrogel is a freeze-thaw method of physical cross-linking, without introducing other chemical reagents, so it is more green and environmentally friendly, non-toxic and pollution-free.

[0014] The present invention does not use chemical cross-linking and does not introduce other chemical reagents, so the preparation process is simple and convenient. After the hydrogel is prepared by the freeze-thaw method, it is immersed in a 1 mol / L phosphate solution to obtain a high-strength PVA conductive hydrogel.

[0015] The polyvinyl alcohol hydrogel prepared in the present invention has ultra-high strength, toughness and good electrical conductivity, and can be well suitable for the application of flexible sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the preparation process of hydrogel; Figure 2 The actual picture of PVA hydrogel after soaking in sodium dihydrogen phosphate aqueous solution, a: before soaking, b: after soaking; Figure 3 The actual picture of PVA hydrogel after soaking in sodium bisulfate aqueous solution, a: before soaking, b: after soaking; Figure 4 The actual picture of PVA hydrogel after soaking in sodium chloride aqueous solution, a: before soaking, b: after soaking; Figure 5The actual picture of PVA hydrogel after soaking in sodium formate aqueous solution, a: before soaking, b: after soaking; Figure 6 The actual picture of PVA hydrogel after soaking in sodium hydrosulfide aqueous solution, a: before soaking, b: after soaking; Figure 7 The actual picture of PVA hydrogel after soaking in sodium nitrite aqueous solution, a: before soaking, b: after soaking; Figure 8 The actual picture of PVA hydrogel after soaking in sodium bisulfite aqueous solution, a: before soaking, b: after soaking; Fig. 9 The actual picture of PVA hydrogel after soaking in sodium citrate aqueous solution, a: before soaking, b: after soaking; Fig.10 The actual picture of PVA hydrogel after soaking in sodium fluoride aqueous solution, a: before soaking, b: after soaking; Fig.11 The actual picture of PVA hydrogel after soaking in sodium acetate aqueous solution, a: before soaking, b: after soaking; Fig.12 The actual picture of PVA hydrogel after soaking in sodium nitrate aqueous solution, a: before soaking, b: after soaking; Fig.13 The actual picture of PVA hydrogel after soaking in sodium bicarbonate aqueous solution, a: before soaking, b: after soaking; Fig.14 The actual picture of PVA hydrogel after soaking in sodium hydrogen phosphate aqueous solution, a: before soaking, b: after soaking; Fig.15 The actual picture of PVA hydrogel after soaking in sodium phosphate aqueous solution, a: before soaking, b: after soaking; Fig.16 The actual picture of PVA hydrogel after soaking in deionized water solution, a: before soaking, b: after soaking; Fig.17 The stretching diagram of hydrogels immersed in different solutions; Fig.18 The maximum stress diagram of hydrogels immersed in different solutions; Fig.19 The elastic modulus diagram of hydrogels immersed in different solutions; Fig. 20 The toughness diagram of hydrogels immersed in different solutions; Fig.21 The infrared characterization images of the hydrogel after being immersed in deionized water and phosphate aqueous solution; Fig. 22 It is the TGA test graph of the hydrogel after soaking in deionized water and phosphate aqueous solution; Fig.23It is the tensile stress-strain curve of the hydrogel without immersion, immersion in deionized water and phosphate aqueous solution; Fig.24 The maximum stress diagram of the hydrogels without immersion, immersion in deionized water, and phosphate aqueous solution; Fig.25 The elastic modulus diagram of the hydrogel without immersion, immersion in deionized water, and phosphate aqueous solution; Fig.26 The toughness diagram of the hydrogels without immersion, immersion in deionized water, and phosphate aqueous solution; Fig. 27 The antifreeze properties of the hydrogel after soaking in deionized water and phosphate aqueous solution, a: before freezing, b: after freezing; Fig.28 This is a graph of 100 stretching cycles of unsoaked PVA hydrogel; Fig.29 This is a graph of 100 stretching cycles of PVA hydrogel after soaking in deionized water; Fig.30 This is a graph of 100 stretching cycles of PVA hydrogel after being immersed in sodium dihydrogen phosphate aqueous solution; Fig.31 This is a graph of 100 stretching cycles of PVA hydrogel after being immersed in a sodium hydrogen phosphate aqueous solution; Fig.32 This is a graph of 100 stretching cycles of PVA hydrogel after being immersed in sodium phosphate aqueous solution; Fig.33 The conductivity diagram of PVA hydrogel after being immersed in different solutions for 12 h Fig.34 This is an electron micrograph of the hydrogel after being soaked in sodium dihydrogen phosphate; Fig.35 This is the electron micrograph of the hydrogel after being soaked in disodium hydrogen phosphate; Fig.36 This is the electron micrograph of the hydrogel after being soaked in sodium phosphate; Fig.37 The tensile stress-strain curves of the hydrogels obtained at different immersion times; Fig.38 The electrical sensor diagrams with different peaks generated by bending the finger at different angles; Fig.39 The electrosensor graph produced by bending the finger; Fig.40 The electrosensorgram produced by wrist flexion; Fig.41 The electrosensorgram produced by elbow flexion; Fig.42 Electrosensory graph of knee flexion. DETAILED DESCRIPTION

[0017] Example 1

[0018] A method for preparing a high-strength and tough PVA conductive hydrogel specifically comprises the following steps: S1, take 5 parts of polyvinyl alcohol and add it to 45 parts of deionized water, cover with plastic wrap, stir and heat in a 95°C water bath to dissolve, to obtain a 10wt% polyvinyl alcohol aqueous solution; S2, cooling the polyvinyl alcohol aqueous solution to room temperature and then pouring it into a mold, sealing it with plastic wrap, freezing it at -20°C for 12 hours, and then thawing it at room temperature for 4 hours to obtain a polyvinyl alcohol hydrogel; S3, soak the polyvinyl alcohol hydrogel in a 1 mol / L sodium dihydrogen phosphate aqueous solution for 12 hours to obtain a high-strength and tough PVA conductive hydrogel. Figure 1 The actual photo of the hydrogel is as follows: Figure 2 shown.

[0019] Example 2

[0020] The difference between Example 2 and Example 1 is that the salt solution used is sodium bisulfate, and the other conditions are exactly the same. Figure 3 shown.

[0021] Example 3

[0022] The difference between Example 3 and Example 1 is that the salt solution used is sodium chloride, and the other conditions are exactly the same. Figure 4 shown.

[0023] Example 4

[0024] The difference between Example 4 and Example 1 is that the salt solution used is sodium formate, and the other conditions are exactly the same. Figure 5 shown.

[0025] Example 5

[0026] The difference between Example 5 and Example 1 is that the salt solution used is sodium hydrosulfide, and the other conditions are exactly the same. Figure 6 shown.

[0027] Example 6

[0028] The difference between Example 6 and Example 1 is that the salt solution used is sodium nitrite, and the other conditions are exactly the same. Figure 7 shown.

[0029] Example 7

[0030] The difference between Example 7 and Example 1 is that the salt solution used is sodium bisulfite, and the other conditions are exactly the same. Figure 8 shown.

[0031] Example 8

[0032] The difference between Example 8 and Example 1 is that the salt solution used is sodium citrate, and the other conditions are exactly the same. Fig. 9 shown.

[0033] Example 9

[0034] The difference between Example 9 and Example 1 is that the salt solution used is sodium fluoride, and the other conditions are exactly the same. Fig.10 shown.

[0035] Example 10

[0036] The difference between Example 10 and Example 1 is that the salt solution used is sodium acetate, and the other conditions are exactly the same. Fig.11 shown.

[0037] Embodiment 11

[0038] The difference between Example 11 and Example 1 is that the salt solution used is sodium nitrate, and the other conditions are exactly the same. Fig.12 shown.

[0039] Example 12

[0040] The difference between Example 12 and Example 1 is that the salt solution used is sodium bicarbonate, and the other conditions are exactly the same. Fig.13 shown.

[0041] Embodiment 13

[0042] The difference between Example 13 and Example 1 is that the salt solution used is disodium hydrogen phosphate, and the other conditions are exactly the same. Figure 1 , the actual photo of the hydrogel is as follows Fig.14 shown.

[0043] Embodiment 14

[0044] The difference between Example 14 and Example 1 is that the salt solution used is sodium phosphate, and the other conditions are exactly the same. Figure 1 , the actual photo of the hydrogel is as follows Fig.15 shown.

[0045] Embodiment 15

[0046] The difference between Example 15 and Example 1 is that the immersion time in the 1 mol / L sodium dihydrogen phosphate aqueous solution is 12 hours, and the other conditions are exactly the same.

[0047] Example 16

[0048] The difference between Example 16 and Example 1 is that the immersion time in the 1 mol / L sodium dihydrogen phosphate aqueous solution is 24 hours, and the other conditions are exactly the same.

[0049] Embodiment 17

[0050] The difference between Example 17 and Example 1 is that the immersion time in the 1 mol / L sodium dihydrogen phosphate aqueous solution is 36 hours, and the other conditions are exactly the same.

[0051] Embodiment 18

[0052] The difference between Example 18 and Example 1 is that the immersion time in the 1 mol / L sodium dihydrogen phosphate aqueous solution is 60 hours, and the other conditions are exactly the same.

[0053] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the salt solution used is replaced by deionized water, and the other conditions are exactly the same. Figure 1 , the actual photo of the hydrogel is as follows Fig.16 shown.

[0054] Examples 1-12 and Comparative Example 1 explore the effect of salt solution on hydrogel. The stress, strain, elastic modulus and toughness tests were performed on the hydrogels obtained in Examples 1-12 and Comparative Example 1. The stress and strain calculation formulas are as follows: δ = F / A Among them, δ is stress, Kpa F - tension, N A——Cross-sectional area, m 3 ε=ΔL / L0 ε——strain, % ΔL - deformation length, mm L0 - original length, mm The tensile stress-strain curve test results of the hydrogels obtained in Examples 1-12 and Comparative Example 1 are shown in Fig.17 By using mechanical instruments to perform tensile tests on hydrogels, we can obtain the maximum stress, elastic modulus, and toughness data of the hydrogels. Fig.18As shown in the figure, it can be concluded that different anions have different effects on the mechanical properties of the hydrogel, among which the NaH2PO4 solution has the greatest effect on the stress of the hydrogel. This may be because the strong ionic strength of sodium dihydrogen phosphate will induce a salting-out effect, reduce the solubility of the PVA chain, and cause dehydration and shrinkage of the polymer. This dehydration effect can increase the crystallinity or physical crosslinking density of the PVA chain, thereby improving the mechanical properties.

[0055] The elastic modulus results of the hydrogels obtained in Examples 1-12 and Comparative Example 1 are shown in Fig.19 From the figure, it can be concluded that different anions have different effects on the elastic modulus of the hydrogel, among which sodium dihydrogen phosphate solution has the greatest effect on the elastic modulus of the hydrogel. This is because sodium dihydrogen phosphate has a strong hydration ability, which can compete for free water in the PVA network, forcing the chain segments to stack more tightly and form a denser cross-linked structure, thereby improving the elastic modulus.

[0056] The toughness test results of the hydrogels obtained in Examples 1-12 and Comparative Example 1 are shown in Fig. 20 , indicating that different anions have different abilities to improve the toughness of PVA hydrogels, among which dihydrogen phosphate ions have the most obvious improvement on the toughness of PVA hydrogels. This is because dihydrogen phosphate forms more hydrogen bonds with PVA hydrogels, and the increase in the number of hydrogen bonds enhances the dynamic cross-linking ability of the hydrogel, making the toughness of the hydrogel stronger. The enhancement of the toughness of the hydrogel makes the hydrogel more resistant to damage and less likely to break.

[0057] By comparison, it was found that the performance of the material was optimal when sodium dihydrogen phosphate was used as the salt solution. On this basis, further attempts were made on other phosphates, and Examples 13 and 14 were tested.

[0058] The hydrogel materials obtained in Example 1, Example 13, Example 14 and Comparative Example 1 were characterized by infrared spectroscopy. Fig.21 With the introduction of salt ions, the shift of the hydroxyl peak in PVA hydrogel becomes more obvious. -1 The typical stretching vibration peak of hydroxyl group is shown at 3430 cm-1. After immersion in phosphate solution, the stretching vibration peak of hydroxyl group becomes more obvious with the increase of sodium ion concentration in the salt solution. The hydroxyl peak of PVA hydrogel immersed in sodium dihydrogen phosphate shifts to 3430 cm-1. -1 The hydroxyl peak of PVA hydrogel soaked in disodium hydrogen phosphate blue shifted to 3426 cm -1 The hydroxyl peak of PVA hydrogel soaked in sodium phosphate blue shifted to 3420 cm -1 , the deviation becomes gradually obvious. This shows that the introduction of phosphate will affect the hydrogen bonding interaction between PVA hydrogel chains, thereby affecting the mechanical properties of PVA hydrogel.

[0059] Thermogravimetric tests (TGA) were performed on the hydrogel materials obtained in Example 1, Example 13, Example 14, and Comparative Example 1, as shown in Fig. 22 . As can be seen from the figure, with the increase in the sodium ion content in the soaked salt solution, the residual substances at the end of the TGA test gradually increase. It shows that during the soaking process, sodium ions penetrate into the interior of the PVA hydrogel network. And when the concentration of the phosphate solution is the same, the more sodium ions can enter the cross-linked network of the PVA hydrogel when soaked in a phosphate solution that can dissociate more sodium ions, resulting in an increase in the residual salt ions, so that the weight of the residual substances gradually increases with the increase in the number of sodium ions in the thermogravimetric analysis results. It shows that the more sodium ions enter the cross-linked network of the PVA hydrogel, the stronger the hydrogen bonds or ion-dipole interactions formed between the polymer chains, and the better the mechanical properties of the hydrogel.

[0060] Stress, strain, elastic modulus, and toughness tests were carried out on the hydrogel materials obtained in Example 1, Example 13, Example 14, Comparative Example 1, and the original polyvinyl alcohol hydrogel without soaking treatment. The test results of the tensile stress-strain curve are shown in Fig.23 as shown, and the bar chart of the maximum stress is as shown in Fig.24 . As can be seen from the figure, with the increase in the number of sodium ions contained in the soaked phosphate solution, the maximum stress gradually increases. That is, the order of the maximum stress is: NaH2PO4 < Na2HPO4 < Na3PO4 It shows that the more sodium ions there are, the stronger the cross-linking density inside the PVA hydrogel and the ion-dipole interaction between the Na ions and the hydrogel, resulting in an increase in the maximum stress of the hydrogel.

[0061] The results of the elastic modulus of the hydrogel materials obtained in Example 1, Example 13, Example 14, and Comparative Example 1 are shown in Fig.25 . As can be seen from the figure, with the increase in the number of sodium ions contained in the soaked phosphate solution, the elastic modulus gradually increases. That is, the order of the elastic modulus from small to large is: NaH2PO4 < Na2HPO4 < Na3PO4. This may be because the high pH of trisodium phosphate promotes the deprotonation of PVA, promotes chain alignment, and increases the crystalline region. At the same time, due to the cross-linking effect of PO4³ - , the cross-linking points inside the hydrogel network will be increased, making the network more rigid.

[0062] The results of the toughness test of the hydrogel materials obtained in Example 1, Example 13, Example 14, and Comparative Example 1 are shown in Fig.26 . As can be seen from the figure, with the increase in the number of sodium ions contained in the soaked phosphate solution, the toughness gradually increases. That is, the order of the toughness from small to large is: NaH2PO4 < Na2HPO4 < Na3PO 4。It is shown that as the number of sodium ions increases, the number of hydrogen bonds and ion-dipole interactions inside the PVA hydrogel increase, enhancing the dynamic cross-linking ability of the hydrogel and making the toughness of the PVA hydrogel increase. The enhanced toughness of the hydrogel makes the hydrogel more resistant to damage and less likely to break.

[0063] The hydrogel materials obtained in Example 1, Example 13, Example 14, and Comparative Example 1 were subjected to a freeze resistance test, that is, the mechanical properties of the materials were tested after being placed at room temperature for 24 h and frozen at -20 °C for 24 h. The results are shown in Fig. 27 , indicating that the PVA hydrogel soaked in the phosphate solution has a certain freeze resistance, and as the number of sodium ions contained in the phosphate solution increases, the freeze resistance of the PVA hydrogel shown is better, that is, NaH2PO4 < Na2HPO4 < Na3PO4. The freeze resistance of the hydrogel can reflect that the PVA hydrogel has good mechanical properties at low temperatures and can avoid brittle fracture. It also shows that the PVA hydrogel can maintain conductivity and flexibility in cold conditions, has good stability, and is more suitable for wearable flexible sensors.

[0064] The cyclic stability tests were carried out on the hydrogel materials obtained in Example 1, Example 13, Example 14, Comparative Example 1, and the unsoaked hydrogel material. The results are shown in Figure 28-32 , and the images formed after 100 stretching cycles of the PVA hydrogel soaked in the phosphate solution are relatively stable, indicating good cyclic stability. It is shown that: the PVA hydrogel soaked in the phosphate solution has good stability and low hysteresis, reflecting the superiority of the mechanical properties of the hydrogel and the reliability of practical applications. It reflects that the PVA hydrogel soaked in the phosphate solution can be applied to flexible sensors that require repeated deformation.

[0065] Electrical property test: The conductivity tests were carried out on the hydrogel materials obtained in Example 1, Example 13, Example 14, Comparative Example 1, and the unsoaked hydrogel material. The results are shown in Fig.33 , and it can be seen from the figure that the conductivity of the hydrogel soaked in the disodium hydrogen phosphate solution is the highest, while the conductivity of the PVA hydrogel soaked in the trisodium phosphate solution with the largest number of sodium ions decreases instead. This may be because when the sodium ion concentration in the hydrogel is too high, the internal cross-linking density and ion-dipole interaction in the hydrogel will be enhanced, resulting in a smaller pore size of the channel for transporting salt ions (electron microscopy Figure 34-36 ), and the migration path of ions is blocked, thus reducing the number of freely moving ions and leading to a decrease in the conductivity of the hydrogel.

[0066] Examples 1, 15 - 18 explored the influence of the soaking time on the hydrogel The tensile stress-strain curves of the hydrogels obtained in Examples 1, 15 - 18 were tested. The results are shown in Fig.37 As shown, it can be seen that when the PVA hydrogel is immersed in a 1 mol / L phosphate aqueous solution, as the immersion time increases, the ion diffusion in the hydrogel becomes more uniform, and the hydrogel cross-linking network becomes more uniform and dense. The enhanced cross-linking between the hydrogel and the ions increases the number of hydrogen bonds between the polymer chains, which increases the cross-linking density of the hydrogel, thereby improving the mechanical properties of the hydrogel. However, if the immersion time in the salt solution is too long (≥60h), the internal structure of the hydrogel will be destroyed, and the excessive ion cross-linking will cause the cross-linking network to be too dense, causing the hydrogel polymer chain to break, causing the hydrogel to change from toughness to brittleness, and the fracture energy will decrease, thereby reducing the mechanical properties of the PVA hydrogel.

[0067] PVA hydrogel soaked in deionized water solution will swell. The entry of water molecules reduces the cross-linking density between the hydrogel polymer chains, reduces the number of hydrogen bonds, and thus reduces the maximum stress of the hydrogel, which is equivalent to reducing the percentage concentration of polyvinyl alcohol in the PVA hydrogel. The swelling of the hydrogel reduces the cross-linking density of the hydrogel, and the cross-linking network in the hydrogel becomes loose, resulting in a decrease in the rigidity of the hydrogel. The originally curled chain segments stretch, making it easier for the polymer chains in the hydrogel to orient along the direction of the external force when stretched, thereby increasing the elongation at break of the hydrogel.

[0068] The polyvinyl alcohol hydrogel obtained by soaking in 1 mol / L sodium dihydrogen phosphate aqueous solution in Example 1 was used as an experimental object to explore its application in flexible sensors.

[0069] Fig.38 These are the electrical sensor diagrams with different peak values ​​generated by bending the finger at different angles, and the bending angles are 30°, 60° and 90° respectively. Fig.39 , Fig.40 , Fig.41 , Fig.42 The electrical sensing diagram formed by bending different parts of the body, which are fingers, wrists, elbows and knees, shows that: the PVA hydrogel sensor soaked in disodium hydrogen phosphate solution is fixed on the human finger, and when the finger is bent to different degrees (30°, 60° and 90°), the electrical signal has significant differences, as shown in Figure 38. The greater the degree of finger bending, the greater the resistance of the PVA hydrogel due to the narrowing of the ion channel, making the peak of the electrical signal more obvious. After verifying that different peak electrical signals can be obtained when the finger is bent to different degrees, the sensor detection ability of other parts of the body is also tested, that is, the sensing ability of the PVA hydrogel sensor for large human body movements such as wrist bending, elbow bending and knee bending is tested. Figure 39~Figure 42The electrical signal sensing diagrams of human finger bending, wrist bending, elbow bending and knee bending are shown respectively. It can be seen from the figure that the peak shape of the electrical signal peak generated by the movement of different parts of the human body is different, and the greater the movement amplitude, the greater the relative resistance change, and the higher the peak value of the electrical signal peak. The peak value of the electrical signal peak generated during knee bending is significantly higher than the peak value of the electrical signal peak formed by the bending movement of other parts. This shows that hydrogel can generate stable, reliable and repeatable electrical signals when applied to flexible sensors, and the movement of joints in various parts of the human body can be more accurately monitored by observing the peak shape of the electrical signal peak and the size of the peak value of the electrical signal peak.

Claims

1. A simple method for preparing high-strength and tough PVA conductive hydrogel, characterized in that: The steps include: S1, adding polyvinyl alcohol into deionized water, dissolving it in a water bath, and obtaining a polyvinyl alcohol aqueous solution; S2, cooling the polyvinyl alcohol aqueous solution obtained in step S1 to room temperature, pouring it into a mold, sealing it with a plastic wrap, freezing it in a refrigerator, and then thawing it to obtain a polyvinyl alcohol hydrogel; S3, soaking the polyvinyl alcohol hydrogel obtained in step S2 in a 1 mol / L salt solution to obtain a high-strength and tough PVA conductive hydrogel; The salt solution is one of sodium dihydrogen phosphate, disodium hydrogen phosphate and sodium phosphate.

2. The simple preparation method of high-toughness PVA conductive hydrogel according to claim 1, characterized in that: The water bath temperature in S1 was 95°C, and the concentration of the final polyvinyl alcohol aqueous solution was 10 wt%.

3. The simple preparation method of high-toughness PVA conductive hydrogel according to claim 1, characterized in that: The freezing temperature in S2 is -20°C and the freezing time is 12 hours.

4. The simple preparation method of high-toughness PVA conductive hydrogel according to claim 1, characterized in that: The concentration of the salt solution in S3 is 1 mol / L.

5. The simple preparation method of high-toughness PVA conductive hydrogel according to claim 1, characterized in that: The soaking time in S3 is 12-60 hours.

6. Application of the PVA conductive hydrogel prepared by the preparation method according to any one of claims 1 to 5 in the field of flexible sensors.

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