PVA hydrogel wettability regulation and control method based on Hough-Merster effect

Abstract

The invention discloses a PVA (Polyvinyl Alcohol) hydrogel wettability regulation and control method based on a Hough-Merster effect, which utilizes the hydration capability difference of different ions in the Hough-Merster effect to realize wide regulation from a super-hydrophilic state to a hydrophobic state by accurately regulating and controlling the hydration structure on the surface of PVA-based hydrogel. By selecting different types of ionic solutions with different concentrations, the surface contact angle of the PVA-based hydrogel can be accurately regulated and controlled within the range of 10-115 degrees. The method disclosed by the invention has universality, can be suitable for wettability regulation and control of all PVA-based hydrogel, does not need additional chemical modification or complex physical treatment, and has the advantages of simplicity, convenience, high efficiency, reversible regulation and the like. Besides, the surface of the adjustable wettability hydrogel can realize personalized adaptation according to different requirements of different parts of a human body on adhesion, and is further expanded to the field of ultra-sensitive myoelectricity monitoring, and a new technical path is provided for development of high-precision human body signal detection and flexible sensors.

Description

Technical Field

[0001] This invention relates to the field of flexible sensors and functional hydrogel materials, specifically a method for controlling the wettability of PVA hydrogels based on the Hofmeister effect. Background Technology

[0002] Hydrogels, due to their excellent flexibility, high water content, good biocompatibility, and responsiveness to external stimuli, have been widely used in biomedicine, flexible electronics, and wearable sensors. Among these applications, the surface wettability of hydrogels plays a crucial role in the adhesion performance, signal transduction, and comfort of bioelectronic devices. However, the surface wettability of most hydrogels is currently fixed, making dynamic control difficult to achieve according to different application requirements, thus limiting their adaptability in areas such as electromyography (EMG) sensing and smart medical patches. Therefore, developing a method to precisely control the surface wettability of hydrogels without chemical modification or complex physical treatments is of great significance for enhancing the application value of hydrogels in smart sensing and bioelectronics.

[0003] Currently, numerous studies have explored methods such as chemical modification, surface nanostructure adjustment, and laser etching to regulate the wettability of materials. For example, inventors have disclosed a method for controlling wettability based on graphene curved photonic crystals, achieving wettability regulation through changes in nanostructure (Patent No.: CN117403313A); there is also a technology using fullerene C60 modified catalysts to control the surface wettability of materials (Patent No.: CN117414830A); and another method has been disclosed for controlling the surface wettability of polytetrafluoroethylene (PTFE) using femtosecond laser processing to obtain a superhydrophobic and anti-icing surface (Patent No.: CN112605531A). These technical solutions also have the following shortcomings: 1. Complex preparation process: Most methods rely on high-cost, high-energy-consumption processing methods such as chemical modification, laser etching, or nanoparticle coating, which are not conducive to large-scale production. 2. Limited control range: Some methods can only adjust the wettability of materials within a specific range, making it difficult to achieve a wide range of adjustment from superhydrophilic to superhydrophobic. 3. Poor reversibility: Once implemented, many techniques lock the wettability state, making dynamic switching under different environmental conditions difficult and limiting their potential in bioelectronic applications with high variability requirements. 4. Limited applicable materials: Most existing methods are designed for specific materials (such as photonic crystals, polytetrafluoroethylene, fullerene catalysts, etc.) and are difficult to apply directly to hydrogel systems. Existing wettability control methods mainly target inorganic materials (such as photonic crystals, polytetrafluoroethylene, catalysts) or organic polymer membranes. Due to the high water content and weak chemical stability of hydrogels, many existing methods cannot be directly applied to hydrogel systems. Therefore, no research or patent has yet explicitly proposed a wettability control method suitable for hydrogels.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical challenges, this invention proposes for the first time a method for controlling the wettability of PVA hydrogels based on the Hofmeister effect. This method achieves precise control of the hydrogel's surface wettability by adjusting the ionic environment on the hydrogel surface, allowing for reversible adjustment between 10° and 115°, thereby effectively meeting the adhesion requirements of different parts of the human body. Specifically, strongly hydrated ions enhance the stability of the hydration layer and improve hydrophilicity, while weakly hydrated ions disrupt the hydration layer and reduce hydrophilicity. By adjusting the types and concentrations of different ions, this invention can provide the required high or low adhesion for different parts of the human body, such as the face, hands, and legs, ensuring the stability and reliability of the hydrogel under various environments.

[0006] To address the above problems, the technical solution of this invention is a method for controlling the wettability of PVA hydrogels based on the Hofmeister effect, comprising the following steps: Step 1: Preparation of PVA-based hydrogels, including PVA-ATMP composite hydrogels, PVA-PNIPAM composite hydrogels, PVA-ATMP-MTMS composite hydrogels, PVA-ATMP-PFOTES composite hydrogels, and PVA-PNIPAM-PFOTES composite hydrogels. Step 2: Ion regulation of hydrogel surface. Prepare ion solutions, select different types of salts, and adjust the concentration according to the characteristics of different ions. Strongly hydrated ions and weakly hydrated ions will be used to adjust the hydrophilicity or hydrophobicity of the hydrogel surface. Take out the frozen hydrogel and quickly immerse it in various salt solutions for 12 hours to make the gel produce the Hofmeister effect in the salt solution, thereby obtaining hydrogels with different wettability surfaces. Step 3: Mechanism analysis of hydrogel wettability regulated by the Hofmeister effect; Step 4: Hydrogel performance testing based on the Hofmeister effect; Step 5: Applying electromyography (EMG) monitoring to different parts of the human body.

[0007] Preferably, in step one, the preparation method of the PVA-ATMP composite gel is as follows: a one-pot method is used to prepare the hydrogel. PVA, ATMP and H2O are mixed and placed in an oil bath at 105℃ for 2 h to form a sol solution. The ratio of PVA, ATMP and H2O is 4:10:30. The sol solution is dropped onto a pre-prepared mold and frozen at -24℃ for 24 h to obtain the PVA-ATMP composite gel.

[0008] According to claim 1, the method for controlling the wettability of PVA hydrogel based on the Hofmeister effect is characterized in that: in step one, the preparation method of PVA-PNIPAM composite hydrogel is as follows: 2 g NIPAM, 0.04 g BIS and 30 mL deionized water are added to a beaker and stirred at room temperature until completely dissolved; 6 g PVA is added and stirred in an oil bath at 90°C for 2 hours. After cooling to room temperature, 600 μL of APS solution (10 wt%) is added and stirred until uniformly mixed. The resulting solution is poured into a mold and heated in an oven at 90°C for 1 hour. It is then placed in a freezer at -24°C for 24 hours and thawed for 24 hours to obtain PVA-PNIPAM composite hydrogel.

[0009] According to claim 1, the method for controlling the wettability of PVA hydrogel based on the Hofmeister effect is characterized in that: in step one, the preparation method of PVA-ATMP-MTMS composite gel is as follows: PVA, ATMP and H2O are mixed and placed in an oil bath at 105℃ for 2 h, the ratio of PVA, ATMP and H2O is 4:10:30, then a certain amount of MTMS is added dropwise and an appropriate amount of acetic acid is added dropwise, the mixture is stirred at 60℃ for 1 h, the sol is dropped onto a pre-prepared mold, and the mixture is frozen at -24℃ for 24 h to obtain PVA-ATMP-MTMS composite gel.

[0010] Preferably, in step one, the preparation method of the PVA-ATMP-PFOTES composite gel is as follows: PVA, ATMP and H2O are mixed and placed in an oil bath at 105℃ for 2 h. The ratio of PVA, ATMP and H2O is 4:10:30. During this period, a certain amount of PFOTES is dissolved in an equal amount of anhydrous ethanol, and a few drops of acetic acid are added for hydrolysis. Then, it is added dropwise to the PVA-ATMP sol solution and stirred at 60℃ for 1 h. The sol solution is then dropped onto a pre-prepared mold and frozen at -24℃ for 24 h to obtain the PVA-ATMP-PFOTES composite gel.

[0011] Preferably, in step one, the preparation method of the PVA-PNIPAM-PFOTES composite hydrogel is as follows: 4 g NIPAM, 0.04 g BIS and 30 ml deionized water are added to a beaker and stirred at room temperature until completely dissolved. 4 g PVA is added and stirred in an oil bath at 90°C for 2 hours. During this time, a certain amount of PFOTES is dissolved in an equal amount of anhydrous ethanol, and a few drops of acetic acid are added for hydrolysis. This solution is added dropwise to the PVA-PNIPAM sol solution and stirred at 60°C for 1 hour. After cooling to room temperature, 600 μL of APS solution (10 wt%) is added and stirred until uniformly mixed. The resulting solution is poured into a mold and heated in a 90°C oven for 1 hour. It is then placed in a -24°C freezer for 24 hours and thawed for 24 hours to obtain the PVA-PNIPAM-PFOTES composite hydrogel.

[0012] Preferably, in step three, the mechanism analysis includes: Fourier transform infrared (FTIR) spectroscopy was used to test hydrogels treated with different ion solutions to investigate the effect of different ions on hydrogen bonds between polymer chains in the hydrogel. The hydrogel surfaces treated with different ionic solutions were characterized using scanning electron microscopy (SEM) to observe the changes in the hydrogel surfaces after treatment with different ionic solutions. The changes in the chemical composition of the hydrogel surface after treatment with different ionic solutions were analyzed using X-ray photoelectron spectroscopy (XPS).

[0013] Preferably, in step four, the performance test includes: Contact angle measurement: The contact angle of the hydrogel surface was measured using a contact angle measuring instrument, and the changes in the contact angle of the hydrogel surface after treatment with different ionic solutions were recorded. The range of contact angle variation was 10° to 115°. Depending on the different ions and concentrations, the hydrogel surface could be adjusted to a strongly hydrophilic or hydrophobic state. Mechanical property measurement: The hydrogel was subjected to compression and tensile tests using a universal testing machine, and the changes in the compression and tensile modulus of the hydrogel after treatment with different ionic solutions were recorded. Conductivity measurement: The hydrogel was tested using an LCR instrument, and the changes in conductivity of the hydrogel after treatment with different ionic solutions were recorded. Electrochemical impedance spectroscopy was used with an electrochemical workstation to measure the interfacial impedance and phase angle changes of hydrogels after treatment with different ionic solutions. Stability testing: The water loss and conductivity changes of hydrogels treated with different ionic solutions were monitored at room temperature.

[0014] Preferably, in step five, electromyography monitoring includes: Electromyographic signals were collected from the face, hands, and legs of the human body using hydrogels treated with different ionic solutions and commercial gels, respectively. The signal-to-noise ratio of electromyographic signals from the face, hands, and legs of the human body was compared between hydrogels treated with different ionic solutions and commercial gels.

[0015] The advantages of this invention compared to existing technologies are: 1. The ion regulation mechanism of this invention has advantages such as simple preparation, precise adjustment, and strong adaptability, and does not rely on complex chemical modifications or changes in physical structure. This method is applicable to PVA-based composite hydrogels such as PVA-ATMP and PVA-PNIPAM, and can be extended to other ion-responsive hydrogel materials, showing broad application prospects. This invention provides a novel strategy for precisely controlling the adhesion of hydrogel surfaces in fields such as flexible electronic devices, smart wearable devices, and electromyography signal monitoring, meeting the personalized needs of different parts of the human body and possessing significant application value.

[0016] 2. This invention is universally applicable to the control of wettability in all PVA-based hydrogels without requiring additional chemical modifications or complex physical treatments. It offers advantages such as simplicity, high efficiency, and reversible adjustment. Furthermore, the adjustable wettability hydrogel surface can be customized to meet the different adhesion requirements of various body parts (e.g., face, hands, legs), further extending to the field of ultrasensitive electromyography monitoring and providing a new technological path for high-precision human signal detection and the development of flexible sensors.

[0017] 3. This invention achieves wettability control between 10° and 115° by adjusting the type and concentration of ions in the environment to change the hydration layer structure on the hydrogel surface. Furthermore, it requires no additional chemical modification, avoids complex processes, and can dynamically switch wettability under different ionic environments, thus improving the applicability of hydrogels in fields such as flexible sensors and bioelectronic devices. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the regulation of hydrogel surface wettability based on the Hofmeister effect.

[0019] Figure 2 The infrared spectra of the hydrogel surfaces after treatment with different ionic solutions in Example 1 are shown.

[0020] Figure 3 XPS data images of the hydrogel surface after treatment with different ionic solutions in Example 1.

[0021] Figure 4 The images are scanning electron microscope (SEM) images of the hydrogel surfaces after treatment with different ionic solutions in Example 1.

[0022] Figure 5 This is a graph showing the change in contact angle of the hydrogel after treatment with solutions containing different types of ions in Example 1.

[0023] Figure 6 This is a graph showing the change in contact angle of the hydrogel after treatment with solutions of different ion concentrations in Example 1.

[0024] Figure 7 The graph shows the changes in contact angle of the hydrogel after treatment with different ionic solutions in Comparative Example 1.

[0025] Figure 8 The graph shows the changes in the contact angle of the hydrogel after treatment with different ionic solutions in Comparative Example 2.

[0026] Figure 9 The graph shows the changes in contact angle of the hydrogel after treatment with different ionic solutions in Comparative Example 3.

[0027] Figure 10 The graph shows the changes in contact angle of the hydrogels after treatment with different ionic solutions in Comparative Example 4.

[0028] Figure 11 The graph shows the changes in contact angle of the hydrogels after treatment with different cationic solutions in Example 1 and Comparative Example 4.

[0029] Figure 12 The graph shows the changes in the mechanical properties of the hydrogel after treatment with different ionic solutions in Example 1.

[0030] Figure 13 The graph shows the changes in conductivity of the hydrogel after treatment with different ionic solutions in Example 1.

[0031] Figure 14 This is a comparison of the impedance and phase angle of the hydrogel and the commercial gel after treatment with different ionic solutions in Example 1.

[0032] Figure 15 This is a graph showing the stability changes of the hydrogel after treatment with different ionic solutions in Example 1.

[0033] Figure 16 The images show electromyography (EMG) signals collected from different parts of the human body by hydrogels treated with different ionic solutions and commercial gels in Example 1.

[0034] Figure 17 This is a comparison chart of the signal-to-noise ratio of hydrogels treated with different ionic solutions and commercial gels for different parts of the human body in Example 1. Detailed Implementation

[0035] To make the content of this invention easier to understand, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0036] The Hofmeister effect refers to the different influences of various ions on the structure and behavior of water molecules in aqueous solutions. In this effect, ions can be classified into "strongly hydrated ions" and "weakly hydrated ions" based on their hydration capacity. Strongly hydrated ions (such as sodium and potassium ions) promote hydrogen bonding between water molecules, enhancing the stability of the hydrated structure, while weakly hydrated ions (such as chloride, bromide, and iodide ions) interfere with the hydrogen bond network between water molecules, reducing the stability of the hydrated structure. PVA (polyvinyl alcohol) is a hydrophilic hydrogel material with strong hydration properties. The surface wettability (including hydrophilicity and hydrophobicity) of hydrogels is significantly affected by hydrated ions. When the surface of a hydrogel is exposed to solutions containing different types of ions, the type and concentration of the ions alter the hydration layer structure of the hydrogel surface, thereby regulating its wettability. Figure 1As shown, the effect of strongly hydrated ions is that when hydrogels come into contact with strongly hydrated ions, these ions enhance the hydrogen bonding between water molecules, forming a more stable hydrated layer. Due to the enhanced hydrated layer, the hydrogel surface exhibits stronger hydrophilicity, the contact angle decreases, and thus the hydrogel surface is more likely to absorb water, exhibiting higher hydrophilicity. Conversely, when hydrogels come into contact with weakly hydrated ions, these ions disrupt the hydrogen bond network between water molecules, damaging the stability of the hydrated layer. Infrared spectroscopy tests on the hydrogel surfaces treated with different ion solutions can prove this point. Figure 2 It can be found that the surface of hydrogel treated with strong hydrated ions (citrate and sulfate) at 3200 cm⁻¹ can withstand temperatures of 100°C. -1 The hydrogen bond peaks in the vicinity are enhanced, while those of weakly hydrated ions (acetate and iodide ions) are weakened. Disruption of the hydration layer reduces the hydrophilicity of the hydrogel surface, resulting in a higher contact angle; that is, the surface tends towards a hydrophobic state. Figure 3 and Figure 4 As shown, further SEM and XPS analyses demonstrate that the microstructure and chemical composition of hydrogel surfaces treated with different ion solutions change. Hydrogel surfaces treated with strongly hydrated ions become smoother, increasing their hydrophilicity; while those treated with weakly hydrated ions exhibit significant wrinkling, leading to decreased hydrophilicity. XPS further shows that the hydrophilic group (O=CO, C=O) content increases on the surface of hydrogels treated with strongly hydrated ions, while the content decreases on those treated with weakly hydrated ions. The hydrophilicity and hydrophobicity of PVA-based hydrogels are primarily determined by the structure of the surface hydration layer. Strongly hydrated ions enhance the stability of the hydration layer, resulting in a lower contact angle and stronger hydrophilicity. Conversely, weakly hydrated ions disrupt the hydration layer, reducing the hydrophilicity of the hydrogel surface and increasing the contact angle, resulting in hydrophobicity. This change in the hydration layer is achieved through the interaction between ions and water molecules, and this regulation can be precisely controlled by altering the types and concentrations of ions in the solution. Figure 5 and Figure 6 Therefore, utilizing the Hofmeister effect to modulate the surface wettability of hydrogels not only allows for precise control of hydrophilicity and hydrophobicity, but also enables the design and optimization of the hydrogel surface as needed. In summary, the mechanism of using the Hofmeister effect to modulate the surface wettability of PVA-based hydrogels mainly relies on the interaction between different ions and the hydration layer on the hydrogel surface. The type and concentration of ions directly affect the stability of the hydration layer, thereby achieving precise control over the hydrophilicity and hydrophobicity of the hydrogel surface.

[0037] This application proposes a PVA-based hydrogel based on the Hofmeister effect, whose properties can be broadly tuned through treatment with different ionic solutions. Utilizing the Hofmeister effect, the wettability of the hydrogel surface can be adjusted, allowing its contact angle to vary from strongly hydrophilic to hydrophobic (10°-115°). This tuning mechanism enables the hydrogel to achieve optimal surface properties according to requirements in different application scenarios. Figure 12 As shown, mechanical property measurements revealed significant changes in both compression and stretching of the hydrogel after treatment with different ionic solutions, allowing for customization of mechanical properties according to application requirements. Regarding electrical conductivity, the Hofmeister effect-tuned hydrogel exhibited controllable changes in conductivity. Figure 13 This ensures efficient conduction of electrophysiological signals. Electrochemical impedance spectroscopy measurements show that ( Figure 16 The hydrogel's ability to modulate interfacial impedance after treatment also depends on ion selection and concentration, and is superior to commercial gels in both aspects, ensuring improved electromyographic signal acquisition quality. The hydrogel's stability is also enhanced; it exhibits minimal water loss and conductivity changes at room temperature, demonstrating high stability. Finally, a comparison was made between electromyographic signal monitoring at different body sites (such as the face, hands, and legs) and commercial gels. Figure 16 and Figure 17 This demonstrates that the hydrogel exhibits excellent electromyographic signal acquisition performance at different sites, providing a higher signal-to-noise ratio and making it widely applicable to fields such as individual motion monitoring and digital health management.

[0038] To verify the ability of the Hofmeister effect to tunably wettability of PVA-based hydrogel surfaces, the change in contact angle (WC) is used as a specific example.

[0039] To verify how different hydrogel surface energies treated with the Hofmeister effect meet the varying adhesion requirements of different parts of the human body and achieve personalized adaptation, the signal-to-noise ratio (SNR) is used as a measure of the acquisition quality of electrophysiological signals. The formula for calculating SNR is as follows:

[0040] Where V signal and V noise These represent the voltage values ​​of the signal and noise, respectively, and N represents the total number of samples.

[0041] Example 1: Step 1: First, PVA, ATMP and H2O (4:10:30) are mixed and placed in an oil bath at 105℃ for 2 h. During this time, a certain amount of PFOTES (2%-10%) is dissolved in an equal amount of anhydrous ethanol, and a few drops of acetic acid are added for pre-hydrolysis treatment. Then, it is added dropwise to the PVA-ATMP sol solution and stirred at 60℃ for 1 h. The sol solution is then dropped onto a pre-prepared mold and frozen for 24 h (-24℃) to obtain the PVA-ATMP-PFOTES (2%-10%) composite gel.

[0042] Step 2: Immerse the prepared PVA-ATMP-PFOTES (2%-10%) composite hydrogel in solutions of sodium citrate, sodium sulfate, disodium hydrogen phosphate, sodium acetate, and sodium iodide of the same concentration for 12 h to allow the gel to produce the Hofmeister effect in the salt solution.

[0043] Step 3: Conduct contact angle tests on the PVA-ATMP-PFOTES (2%-10%) composite hydrogels treated with the Hofmeister effect, and record the changes in contact angle after ion solution treatment.

[0044] Step 4: Electromyography (EMG) data were collected from different parts of the human body (face, hands, and legs) using gel patches soaked in sodium sulfate, disodium hydrogen phosphate, and sodium iodide, respectively, and the signal-to-noise ratio was calculated.

[0045] Comparative Example 1: Step 1: One-pot preparation of hydrogel. PVA, ATMP and H2O (4:10:30) were mixed and reacted in an oil bath at 105℃ for 2 h to form a sol solution. The sol solution was then dropped onto a pre-prepared mold and frozen for 24 h (-24℃) to obtain a PVA-ATMP composite gel.

[0046] Step 2: Prepare ATMP-PVA hydrogel using a one-pot method. Immerse the prepared hydrogel in a solution of sodium citrate, sodium sulfate, disodium hydrogen phosphate, sodium acetate, and sodium iodide of the same concentration for 12 hours to allow the gel to produce the Hofmeister effect in the salt solution.

[0047] Step 3: Conduct contact angle tests on the PVA-ATMP hydrogels treated with the Hofmeister effect and record the changes in contact angle after ion solution treatment.

[0048] This comparative example compares the effect of PFOTES addition on the initial wettability of PVA-based composite hydrogels. It shows that compared with Example 1, the addition of PFOTES increases the initial surface contact angle of the PVA-based composite hydrogel, and is expected to increase the range of contact angle variation.

[0049] Comparative Example 2: Step 1: First, add 2 g NIPAM, 0.04 g BIS, and 30 mL deionized water to a beaker and stir at room temperature until completely dissolved. Then, add 6 g PVA and stir in an oil bath at 90 °C for 2 hours. After cooling to room temperature, add 600 μL of APS solution (10 wt%) and stir until homogeneous. Pour the resulting solution into a mold and heat in a 90 °C oven for 1 hour. Subsequently, freeze it in a -24 °C freezer for 24 hours, then thaw for 24 hours. Finally, a PVA-PNIPAM composite hydrogel is obtained.

[0050] Step 2: Immerse the prepared PVA-PNIPAM composite hydrogel in solutions of sodium citrate, sodium sulfate, disodium hydrogen phosphate, sodium acetate, and sodium iodide of the same concentration for 12 h to allow the gel to produce the Hofmeister effect in the salt solution.

[0051] Step 3: Conduct contact angle tests on the PVA-PNIPAM hydrogels treated with the Hofmeister effect and record the changes in contact angle after ion solution treatment.

[0052] This comparative example compares the differences in the initial wettability of ATMP and PNIPAM on PVA-based composite hydrogels. It shows that, compared with Example 1, although PNIPAM has a slightly higher initial surface contact angle than ATMP, the change in the surface contact angle of the hydrogel after the Hofmeister effect has not made a significant breakthrough.

[0053] Comparative Example 3: Step 1: First, PVA, ATMP and H2O (4:10:30) were mixed and placed in an oil bath at 105℃ for 2 h. Then, a certain amount of MTMS (2%-10%) was added dropwise and an appropriate amount of acetic acid was added. The mixture was stirred at 60℃ for 1 h. The sol solution was then dropped onto a pre-prepared mold and frozen for 24 h (-24℃) to obtain a PVA-ATMP-MTMS (2%-10%) composite gel.

[0054] Step 2: Immerse the prepared PVA-ATMP-MTMS (2%-10%) composite hydrogel in solutions of sodium citrate, sodium sulfate, disodium hydrogen phosphate, sodium acetate, and sodium iodide of the same concentration for 12 h to allow the gel to produce the Hofmeister effect in the salt solution.

[0055] Step 3: Conduct contact angle tests on the PVA-ATMP-MTMS (2%-10%) composite hydrogels treated with the Hofmeister effect, and record the changes in contact angle after ion solution treatment.

[0056] This comparative example compares the effects of PFOTES and MTMS on the initial wettability of PVA-based hydrogels. It shows that compared with Example 1, PFOTES can increase the initial surface contact angle of PVA-based hydrogels more significantly, and the Hofmeister effect results in a wider range of changes in the wettability of the hydrogel surface.

[0057] Comparative Example 4: Step 1: First, add 4 g NIPAM, 0.04 g BIS, and 30 mL deionized water to a beaker and stir at room temperature until completely dissolved. Then, add 4 g PVA and stir in an oil bath at 90°C for 2 hours. During this time, dissolve a certain amount of PFOTES (2%-10%) in an equal volume of anhydrous ethanol and add a few drops of acetic acid for hydrolysis. Then, add this solution dropwise to the PVA-PNIPAM sol solution and stir at 60°C for 1 hour. After cooling to room temperature, add 600 μL of APS solution (10 wt%) and stir until homogeneous. Pour the resulting solution into a mold and heat in a 90°C oven for 1 hour. Subsequently, freeze it in a -24°C freezer for 24 hours and then thaw it for 24 hours. Finally, a PVA-PNIPAM-PFOTES (2%-10%) composite hydrogel is obtained.

[0058] Step 2: Immerse the prepared PVA-PNIPAM-PFOTES (2%-10%) composite hydrogel in solutions of sodium citrate, sodium sulfate, disodium hydrogen phosphate, sodium acetate, and sodium iodide of the same concentration for 12 h to allow the gel to produce the Hofmeister effect in the salt solution.

[0059] Step 3: Conduct contact angle tests on the PVA-PNIPAM-PFOTES (2%-10%) composite hydrogels treated with the Hofmeister effect, and record the changes in contact angle after ion solution treatment.

[0060] This comparative example compares the effects of ATMP and PNIPAM on the wettability of PVA-based composite hydrogels with the addition of PFOTES. It shows that, compared with Example 1, the wettability of the PVA-ATMP-PFOTES composite hydrogel varies more widely after treatment with the same ionic solution than that of the PVA-PNIPAM-PFOTES composite hydrogel.

[0061] Based on the above embodiments and comparative examples, it can be concluded that: After being influenced by the Hofmeister effect, the surface contact angle of PVA-based composite hydrogels can vary from 10° to 115°.

[0062] The hydrogel treated based on the Hofmeister effect has tunable mechanical and electrical properties, with a compressive modulus ranging from 44.29 kPa to 1140.88 kPa, a tensile modulus ranging from 42.98 kPa to 825.71 kPa, and a conductivity ranging from 2.49 S / m to 19.58 S / m.

[0063] Because hydrogels have tunable wettability, and the impedance of hydrogels treated with ionic solutions is significantly lower than that of commercial gels at 1 Hz. PVA-ATMP-PFOTES (8%) treated with sodium sulfate, disodium hydrogen phosphate, and sodium iodide showed excellent signal-to-noise ratios (greater than 25 dB) in electromyography monitoring of different human body parts (face, hand, and leg), all of which were superior to commercial gels.

[0064] This invention proposes a method to achieve tunable wettability of PVA-based composite hydrogels using the Hofmeister effect. However, existing inventions do not have detailed methods for easily and accurately controlling the wettability of hydrogels. Most rely on nanostructures, optimization of material chemical properties and pore structure, or coating with hydrophilic or hydrophobic catalysts to control the wettability of materials.

[0065] The method of this invention is applicable to multiple fields such as customized exercise training monitoring and personalized health management.

[0066] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling the wettability of PVA hydrogels based on the Hofmeister effect, characterized in that, Includes the following steps: Step 1: Preparation of PVA-based hydrogels, including PVA-ATMP composite hydrogels, PVA-PNIPAM composite hydrogels, PVA-ATMP-MTMS composite hydrogels, PVA-ATMP-PFOTES composite hydrogels, and PVA-PNIPAM-PFOTES composite hydrogels. Step 2: Ion regulation of hydrogel surface. Prepare ion solutions, select different types of salts, and adjust the concentration according to the characteristics of different ions. Strongly hydrated ions and weakly hydrated ions will be used to adjust the hydrophilicity or hydrophobicity of the hydrogel surface. Take out the frozen hydrogel and quickly immerse it in various salt solutions for 12 hours to make the gel produce the Hofmeister effect in the salt solution, thereby obtaining hydrogels with different wettability surfaces. Step 3: Mechanism analysis of hydrogel wettability regulated by the Hofmeister effect; Step 4: Hydrogel performance testing based on the Hofmeister effect; Step 5: Applying electromyography (EMG) monitoring to different parts of the human body.

2. The method for controlling the wettability of PVA hydrogel based on the Hofmeister effect according to claim 1, characterized in that: In step one, the preparation method of PVA-ATMP composite gel is as follows: hydrogel is prepared by one-pot method. PVA, ATMP and H2O are mixed and placed in an oil bath at 105℃ for 2 h to form a sol solution. The ratio of PVA, ATMP and H2O is 4:10:

30. The sol solution is dropped onto a pre-prepared mold and frozen at -24℃ for 24 h to obtain PVA-ATMP composite gel.

3. The method for controlling the wettability of PVA hydrogel based on the Hofmeister effect according to claim 1, characterized in that: In step one, the preparation method of PVA-PNIPAM composite hydrogel is as follows: 2 g NIPAM, 0.04 g BIS and 30 ml deionized water are added to a beaker and stirred at room temperature until completely dissolved; 6 g PVA is added and stirred in an oil bath at 90°C for 2 hours. After cooling to room temperature, 600 μL of APS solution (10 wt%) is added and stirred until uniformly mixed. The resulting solution is poured into a mold and heated in an oven at 90°C for 1 hour. It is then placed in a freezer at -24°C for 24 hours and thawed for 24 hours to obtain PVA-PNIPAM composite hydrogel.

4. The method for controlling the wettability of PVA hydrogel based on the Hofmeister effect according to claim 1, characterized in that: In step one, the preparation method of PVA-ATMP-MTMS composite gel is as follows: PVA, ATMP and H2O are mixed and reacted in an oil bath at 105℃ for 2 h. The ratio of PVA, ATMP and H2O is 4:10:

30. Then, a certain amount of MTMS and an appropriate amount of acetic acid are added dropwise. The mixture is stirred at 60℃ for 1 h. The sol solution is then dropped onto a pre-prepared mold and frozen at -24℃ for 24 h to obtain PVA-ATMP-MTMS composite gel.

5. The method for controlling the wettability of PVA hydrogel based on the Hofmeister effect according to claim 1, characterized in that: In step one, the preparation method of PVA-ATMP-PFOTES composite gel is as follows: PVA, ATMP and H2O are mixed and placed in an oil bath at 105℃ for 2 h. The ratio of PVA, ATMP and H2O is 4:10:

30. During the reaction, a certain amount of PFOTES is dissolved in an equal amount of anhydrous ethanol, and a few drops of acetic acid are added for hydrolysis. Then, the PFOTES is added dropwise to the PVA-ATMP sol solution and stirred at 60℃ for 1 h. The sol solution is then dropped onto a pre-prepared mold and frozen at -24℃ for 24 h to obtain the PVA-ATMP-PFOTES composite gel.

6. The method for controlling the wettability of PVA hydrogel based on the Hofmeister effect according to claim 1, characterized in that: In step one, the preparation method of PVA-PNIPAM-PFOTES composite hydrogel is as follows: 4 g NIPAM, 0.04 g BIS and 30 ml deionized water are added to a beaker and stirred at room temperature until completely dissolved. 4 g PVA is added and stirred in an oil bath at 90°C for 2 hours. During this time, a certain amount of PFOTES is dissolved in an equal amount of anhydrous ethanol, and a few drops of acetic acid are added for hydrolysis. This solution is added dropwise to the PVA-PNIPAM sol solution and stirred at 60°C for 1 hour. After cooling to room temperature, 600 μL of APS solution (10 wt%) is added and stirred until uniformly mixed. The resulting solution is poured into a mold and heated in a 90°C oven for 1 hour. It is then placed in a -24°C freezer for 24 hours and thawed for 24 hours to obtain the PVA-PNIPAM-PFOTES composite hydrogel.

7. The method for controlling the wettability of PVA hydrogel based on the Hofmeister effect according to claim 1, characterized in that: In step three, the mechanism analysis includes: Fourier transform infrared (FTIR) spectroscopy was used to test hydrogels treated with different ion solutions to investigate the effect of different ions on hydrogen bonds between polymer chains in the hydrogel. The hydrogel surfaces treated with different ionic solutions were characterized using scanning electron microscopy (SEM) to observe the changes in the hydrogel surfaces after treatment with different ionic solutions. The changes in the chemical composition of the hydrogel surface after treatment with different ionic solutions were analyzed using X-ray photoelectron spectroscopy (XPS).

8. The method for controlling the wettability of PVA hydrogel based on the Hofmeister effect according to claim 1, characterized in that: In step four, the performance test includes: Contact angle measurement: The contact angle of the hydrogel surface was measured using a contact angle measuring instrument, and the changes in the contact angle of the hydrogel surface after treatment with different ionic solutions were recorded. The range of contact angle variation was 10° to 115°. Depending on the different ions and concentrations, the hydrogel surface could be adjusted to a strongly hydrophilic or hydrophobic state. Mechanical property measurement: The hydrogel was subjected to compression and tensile tests using a universal testing machine, and the changes in the compression and tensile modulus of the hydrogel after treatment with different ionic solutions were recorded. Conductivity measurement: The hydrogel was tested using an LCR instrument, and the changes in conductivity of the hydrogel after treatment with different ionic solutions were recorded. Electrochemical impedance spectroscopy was used with an electrochemical workstation to measure the interfacial impedance and phase angle changes of hydrogels after treatment with different ionic solutions. Stability testing: The water loss and conductivity changes of hydrogels treated with different ionic solutions were monitored at room temperature.

9. The method for controlling the wettability of PVA hydrogel based on the Hofmeister effect according to claim 1, characterized in that: In step five, electromyography monitoring includes: Electromyographic signals were collected from the face, hands, and legs of the human body using hydrogels treated with different ionic solutions and commercial gels, respectively. The signal-to-noise ratio of electromyographic signals from the face, hands, and legs of the human body was compared between hydrogels treated with different ionic solutions and commercial gels.

Images