Swelling-resistant self-adhesive hydrogel sensor based on multiple dynamic crosslinking and preparation method and application of swelling-resistant self-adhesive hydrogel sensor

Abstract

The invention discloses a dense dual-network anti-swelling self-adhesion hydrogel sensor based on multiple dynamic crosslinking as well as a preparation method and application of the dense dual-network anti-swelling self-adhesion hydrogel sensor. The preparation method specifically comprises the following steps: adding acrylic acid, hydroxyethyl methylacrylate, a chemical cross-linking agent and a photoinitiator into deionized water, and stirring at room temperature until the materials are completely dissolved; then, adding a certain amount of tannic acid and chitosan quaternary ammonium salt into the mixture, and fully stirring until a uniform precursor solution is formed; then, the precursor solution is transferred into a reaction template, and the reaction template is placed under an ultraviolet lamp to initiate curing; therefore, the anti-swelling hydrogel can be obtained, in various solvents, the material has good anti-swelling performance and shows excellent adhesion and sensing durability, and the problems that a traditional hydrogel sensor is limited in application in a wet environment and loses sensing performance are solved. The system can be widely applied to human body motion monitoring and underwater information transmission in a water environment, and underwater communication is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogel sensors, and particularly relates to an anti-swelling self-adhesive hydrogel sensor based on multiple dynamic crosslinking, and a preparation method and application thereof. Technical Background

[0002] With the increase in the population participating in underwater exploration or underwater entertainment such as swimming and diving, underwater sensing technology plays an important role in ensuring the safety of underwater activities. However, traditional conductive gels are unstable in aquatic environments. First, due to the numerous hydrophilic groups in the hydrogel polymer backbone, traditional gels can absorb a large amount of water and are accompanied by volume swelling, resulting in the loss of the initial network structure and mechanical properties. In addition, the hydrated layer formed on the surface prevents the molecular-level bridging and interaction between the conductive gel and the substrate, thereby reducing the adhesion strength of the conductive gel. These problems seriously hinder the application of wearable sensors based on traditional conductive gels in underwater sensing.

[0003] Some effective strategies have been adopted for the extensive research and development of anti-swelling conductive hydrogels suitable for underwater environments, such as encapsulation, hydrophobic networks, etc., to achieve the stability of the structure and function of conductive gels in underwater environments. The encapsulation structure mainly isolates the contact between the conductive gel and the water environment by encapsulating the conductive gel with an additional waterproof film, which is the simplest method to obtain a stable conductive gel underwater and realize its underwater sensing application. However, due to the mismatch in mechanical properties between the encapsulation layer and the sensing layer, the sensing signal is weakened to a certain extent, affecting its accuracy; while the hydrophobic polymer network effectively improves the swelling ability and underwater stability of the conductive gel by inhibiting the interfacial diffusion of substances dissolved in water. However, excessive crosslinking of the hydrophobic network will lead to network brittleness, affecting the monitoring range of the hydrogel sensor, and the hydrophobic properties of existing conductive gels are still not perfect, and their practical applications are greatly limited. Therefore, it is particularly important to develop anti-swelling hydrogels with a wide strain range and self-adhesion. Summary of the Invention

[0004] Aiming at the limitations in current practical applications, the purpose of the present invention is to provide a dense double-network anti-swelling self-adhesive hydrogel sensor based on multiple dynamic crosslinking, and a preparation method and application thereof.

[0005] A preparation method of a dense double-network anti-swelling self-adhesive hydrogel sensor based on multiple dynamic crosslinking. First, acrylic acid and 2-hydroxyethyl methacrylate are copolymerized, and cationic polymer chitosan quaternary ammonium salt is used as the network skeleton of the hydrogel to construct a double-network structure; then tannic acid capable of improving the adhesion and mechanical properties of the gel material is added to make a precursor solution; finally, the precursor solution is photocured under ultraviolet light to obtain an anti-swelling self-adhesive hydrogel.

[0006] The preparation method of the above-mentioned dense double-network anti-swelling self-adhesive hydrogel sensor based on multiple dynamic crosslinking includes the following specific steps: (1) Dissolve the reaction monomers acrylic acid, 2-hydroxyethyl methacrylate, the chemical crosslinking agent, and the photoinitiator in deionized water until completely dissolved at room temperature to obtain Solution 1; (2) Weigh a certain mass of the cationic polymer chitosan quaternary ammonium salt and tannic acid and add them to Solution 1, and stir evenly at room temperature to obtain Solution 2; (3) Transfer Solution 2 in step (2) to a reaction mold, place it under an ultraviolet lamp for photocuring, and take it out to obtain an anti-swelling self-adhesive hydrogel.

[0007] Further, in Solution 1 described in step (1), the mass ratio of acrylic acid: 2-hydroxyethyl methacrylate: chemical crosslinking agent: photoinitiator: deionized water is: 300: 100: 1: 4: 1000.

[0008] Further, the chemical crosslinking agent described in step (1) is N,N'-methylenebisacrylamide.

[0009] Further, the photoinitiator described in step (1) is a free radical initiator, including photoinitiator I2959.

[0010] Further, in Solution 2 described in step (2), the mass ratio of chitosan quaternary ammonium salt to tannic acid is: 0.1~0.5: 0.2 - 0.6; the chitosan quaternary ammonium salt is used to provide conductivity, form electrostatic interaction with carboxylate groups, improve its crosslinking density, and reduce the anti-swelling performance of the hydrogel; the adhesion unit tannic acid is used to enhance the adhesion of the hydrogel, improve the stability of its underwater adhesion, and form hydrogen bonds with the hydrogel network to further enhance the crosslinking of the hydrogel.

[0011] Further, the wavelength of the ultraviolet lamp described in step (3) is 365 nm, the power is 20 W, and the irradiation duration is 1 h.

[0012] An anti-swelling self-adhesive hydrogel sensor prepared by the above method.

[0013] The application of the above anti-swelling self-adhesive hydrogel sensor in sensor materials.

[0014] The technical principle of the present invention: Due to the multiple hydrogen bonds formed between the abundant hydroxyl and carboxyl groups in acrylic acid, tannic acid, and quaternary ammonium salt of chitosan, as well as the electrostatic interaction and polymer chain entanglement between poly(acrylic acid-hydroxyethyl methacrylate) and quaternary ammonium salt of chitosan, the hydrogel can form a highly cross-linked network structure, ensuring the structural integrity and stability of the hydrogel underwater. At the same time, due to the construction of the double-network structure, the hydrogel has remarkable tensile properties, with an elongation rate reaching 990%, showing a wide sensing range. And due to the covalent / non-covalent synergistic adhesion effect formed between the catechol groups in tannic acid molecules and the substrate, the hydrogel exhibits excellent adhesion to a variety of substrates. Therefore, the sensor based on the hydrogel can be effectively used for real-time motion monitoring in the underwater environment and as an underwater communication device to transmit Morse code, realizing efficient underwater information transmission.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) By using the copolymerization of acrylic acid and hydroxyethyl methacrylate and the cationic polymer quaternary ammonium salt of chitosan as the network skeleton of the hydrogel, a double-network structure is constructed, and due to the electrostatic interaction and multiple hydrogen bond interactions between the chains, the anti-swelling performance and mechanical properties of the hydrogel are greatly improved.

[0016] (2) After adding tannic acid, the adhesion and mechanical properties of the gel material are improved, enabling the material to have excellent adhesion and mechanical properties, with good binding force to the substrate, and ensuring wide strain range and adhesion stability in the water environment.

[0017] (3) The hydrogel prepared by the present invention has a stable preparation process, is easy to operate, can be used for a long time, and meets the requirements of underwater motion monitoring and communication. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 Shows the mechanical properties of the gel in Example 2: stress-strain curve.

[0020] Figure 2 Shows the adhesion performance and cyclic stability of the gel in Example 2 for different substrates.

[0021] Figure 3 Shows the anti-swelling performance of the gel in Example 2 in different solvents.

[0022] Figure 4Shows the sensing performance of the gel in Example 2.

[0023] Figure 5 Shows the sensing and monitoring performance of the gel in Example 2 for different parts of the human body.

[0024] Figure 6 Shows the performance of the gel in Example 2 for underwater communication via Morse code. Detailed implementation manners

[0025] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0026] Unless otherwise specified, the equipment used in the following examples represents conventional equipment in the art. Unless otherwise specified, the reagents used represent common products in the art. Those not described in detail in the following examples can be achieved by conventional means in the art.

[0027] This embodiment provides a preparation method of an anti-swelling self-adhesive hydrogel, which specifically includes the following steps: Example 1 Dissolve 3.0 g of acrylic acid, 1.0 g of 2-hydroxyethyl methacrylate, 10 mg of chemical cross-linking agent N,N'-methylenebisacrylamide, and 40 mg of photoinitiator I2959 in 10.0 g of deionized water. Mix the monomers evenly in the air and stir well for 30 min until completely dissolved to obtain Solution 1.

[0028] Further add 0.1 g of cationic polymer chitosan quaternary ammonium salt and 0.4 g of tannic acid to Solution 1, mix evenly, and stir well for 1 h until completely dissolved to obtain a hydrogel precursor solution.

[0029] Transfer the prepared hydrogel precursor solution to a reaction mold, and further polymerize it under ultraviolet light (365 nm, 20 W) for 1 h to prepare a hydrogel material.

[0030] Example 2 Dissolve 3.0 g of acrylic acid, 1.0 g of 2-hydroxyethyl methacrylate, 10 mg of chemical cross-linking agent N,N'-methylenebisacrylamide, and 40 mg of photoinitiator I2959 in 10.0 g of deionized water. Mix the monomers evenly in the air and stir well for 30 min until completely dissolved to obtain Solution 1.

[0031] Further add 0.3 g of cationic polymer chitosan quaternary ammonium salt and 0.4 g of tannic acid to Solution 1, mix evenly, and stir well for 1 h until completely dissolved to obtain a hydrogel precursor solution.

[0032] Transfer the prepared hydrogel precursor solution into a reaction mold, and further polymerize it under ultraviolet light (365 nm, 20 W) for 1 h to prepare a hydrogel material with anti-swelling self-adhesion.

[0033] Example 3 Dissolve 3.0 g of acrylic acid, 1.0 g of 2-hydroxyethyl methacrylate, 10 mg of chemical cross-linking agent N,N'-methylenebisacrylamide, and 40 mg of photoinitiator I2959 in 10.0 g of deionized water. Mix the monomers evenly in air and stir well for 30 min until completely dissolved to obtain Solution 1.

[0034] Further add 0.5 g of cationic polymer chitosan quaternary ammonium salt and 0.4 g of tannic acid to Solution 1, mix evenly, and stir well for 1 h until completely dissolved to obtain a hydrogel precursor solution.

[0035] Transfer the prepared hydrogel precursor solution into a reaction mold, and further polymerize it under ultraviolet light (365 nm, 20 W) for 1 h to prepare a hydrogel material.

[0036] Example 4 Dissolve 3.0 g of acrylic acid, 1.0 g of 2-hydroxyethyl methacrylate, 10 mg of chemical cross-linking agent N,N'-methylenebisacrylamide, and 40 mg of photoinitiator I2959 in 10.0 g of deionized water. Mix the monomers evenly in air and stir well for 30 min until completely dissolved to obtain Solution 1.

[0037] Further add 0.3 g of cationic polymer chitosan quaternary ammonium salt and 0.2 g of tannic acid to Solution 1, mix evenly, and stir well for 1 h until completely dissolved to obtain a hydrogel precursor solution.

[0038] Transfer the prepared hydrogel precursor solution into a reaction mold, and further polymerize it under ultraviolet light (365 nm, 20 W) for 1 h to prepare a hydrogel material.

[0039] Example 5 Dissolve 3.0 g of acrylic acid, 1.0 g of 2-hydroxyethyl methacrylate, 10 mg of chemical cross-linking agent N,N'-methylenebisacrylamide, and 40 mg of photoinitiator I2959 in 10.0 g of deionized water. Mix the monomers evenly in air and stir well for 30 min until completely dissolved to obtain Solution 1.

[0040] 0.3 g of cationic polymer chitosan quaternary ammonium salt and 0.6 g of tannic acid were further added to Solution 1, mixed evenly, and stirred thoroughly for 1 h until completely dissolved, and then a hydrogel precursor solution was obtained.

[0041] The prepared hydrogel precursor solution was transferred to a reaction mold and further polymerized under ultraviolet light (365 nm, 20 W) for 1 h to prepare a hydrogel material.

[0042] Comparative Example 1 (without adding cationic polymer chitosan quaternary ammonium salt) 3.0 g of acrylic acid, 1.0 g of 2-hydroxyethyl methacrylate, 10 mg of chemical crosslinking agent N,N'-methylenebisacrylamide, and 40 mg of photoinitiator I2959 were dissolved in 10.0 g of deionized water. The monomers were mixed evenly in air and stirred thoroughly for 30 min until completely dissolved to obtain Solution 1.

[0043] 0.4 g of tannic acid was further added to Solution 1, mixed evenly, and stirred thoroughly for 1 h until completely dissolved, and then a hydrogel precursor solution was obtained.

[0044] The prepared hydrogel precursor solution was transferred to a reaction mold and further polymerized under ultraviolet light (365 nm, 20 W) for 1 h to prepare a hydrogel material.

[0045] Comparative Example 2 (without adding adhesion unit tannic acid) 3.0 g of acrylic acid, 1.0 g of 2-hydroxyethyl methacrylate, 10 mg of chemical crosslinking agent N,N'-methylenebisacrylamide, and 40 mg of photoinitiator I2959 were dissolved in 10.0 g of deionized water. The monomers were mixed evenly in air and stirred thoroughly for 30 min until completely dissolved to obtain Solution 1.

[0046] 0.3 g of cationic polymer chitosan quaternary ammonium salt was further added to Solution 1, mixed evenly, and stirred thoroughly for 1 h until completely dissolved, and then a hydrogel precursor solution was obtained.

[0047] The prepared hydrogel precursor solution was transferred to a reaction mold and further polymerized under ultraviolet light (365 nm, 20 W) for 1 h to prepare a hydrogel material.

[0048] Performance Test The gel prepared in Example 2 was subjected to performance testing according to the following steps: Test 1: Mechanical properties of the gel Cut the gel material into rectangles and measure the mechanical properties of the samples using a computer-controlled electronic universal testing machine. Fix the samples between two clamps and uniaxially stretch them at a rate of 50 mm / min.

[0049] Test Two: Adhesion Performance of the Gel Cut the samples into rectangles of the same size (2 mm in thickness, 10 mm×10 mm in area). Attach different substrates to the upper and lower surfaces of the sensor respectively, place the sample in the middle, first apply a load of 10 N and pre-press for 120 s, then pull the upper and lower sensors apart at a speed of 60 mm / min until failure, and determine the adhesion strength of the material according to the adhesion force curve.

[0050] Test Three: Swelling Performance of the Gel in Different Solutions Test the swelling performance in different solutions. At room temperature, record the initial mass of the gel, soak it in different solutions, including solutions with different pH values and common organic reagents, record the mass of the gel after a certain time, and determine the swelling ratio of the gel according to the relative change in mass. It can be seen that the material can maintain good anti-swelling performance and exhibits excellent anti-swelling performance in aqueous solutions with pH = 3 - 11, common organic solvents, and artificial seawater. Moreover, quaternary ammonium salt of chitosan has a very important influence on maintaining the anti-swelling performance of the gel.

[0051] Test Four: Electrical Properties of the Gel Connect the gel material to a digital source meter through copper tape for relevant tests on sensing performance. It can be found from the figure that the hydrogel sensor exhibits excellent sensing performance, with clear output signals, high reversibility, and stable sensing signals. This indicates that it has great application potential in monitoring human mild and intense movements.

[0052] Figure 1 For the mechanical properties of the hydrogel of the present invention, as Figure 1 shown (Example Two), even in the state of large stretching or 180° torsion, it can maintain its structural integrity. The mechanical properties of the hydrogel are the best, with a strain rate of 990% and a fracture strength of 96 kPa. The introduction of quaternary ammonium salt of chitosan and tannic acid enhances the mechanical properties of the gel, and both the stress and strain of the hydrogel are significantly enhanced (Comparative Example One, Comparative Example Two).

[0053] Figure 2For the adhesion performance of the hydrogel of the present invention (Example 2), the hydrogel exhibits excellent interfacial adhesion characteristics and can form a tight bond with the surfaces of various organic and inorganic materials. Tannic acid (TA) molecules contain abundant catechol groups and polar oxygen-containing functional groups, which can generate various interactions with different interfaces. The hydrogel shows strong interfacial binding ability to inorganic materials such as stainless steel (59.1 kPa), aluminum sheet (58.1 kPa), and glass (53.8 kPa), and also shows good adaptability to organic materials such as wood (40.9 kPa), PMMA (38.8 kPa), PET (38.5 kPa), rubber (33.0 kPa), and PTFE (17.5 kPa). It is worth noting that after 10 consecutive adhesion cycle tests, the adhesion strength between the hydrogel and the stainless steel substrate basically does not decay, which confirms its excellent interfacial adhesion.

[0054] Figure 3 For the anti-swelling performance of the hydrogel of the present invention (Example 2), it shows excellent anti-swelling performance in a variety of liquid environments. The equilibrium swelling ratio in water is <5.5%, and in organic solvents such as toluene, due to the dehydration shrinkage effect caused by solvent exchange, the swelling ratio of the hydrogel shows a negative value. And it maintains excellent anti-swelling performance in a wide pH range from 3 to 9, and the swelling rate is within 15%, with excellent acid-base stability.

[0055] Figure 4 For the sensing performance of the hydrogel sensor of the present invention (Example 2), in the strain ranges of 0 - 60%, 60 - 200%, and 200 - 500%, the GF values are 0.77, 0.98, and 1.13 respectively. The hydrogel sensor can accurately and continuously identify the cyclic deformation process of small and large strains (from 10% to 500%), with clear output signals and high reversibility.

[0056] Figure 5 For the motion behavior monitoring of the hydrogel of the present invention (Example 2), by connecting the hydrogel sensor to different body parts, during movement, the real-time motion signals of different joints can be monitored, including fingers, wrists, and elbows. When the joint bends, the resistance signal responds uniformly. Different joint parts' motions can be identified through different curve shapes and intensities, indicating that the sensor has the ability to monitor human motion signals in air and underwater. In addition, multiple bends of the same component show almost the same signals, which proves the reliability and repeatability of the hydrogel sensor.

[0057] Figure 6The anti-swelling hydrogel of the present invention transmits information in real time through underwater communication (Example 2). Different finger bending angles correspond to different Morse code symbols. The bending states (30°) and bending states (90°) on the finger are defined as "." and "-" respectively. Three small bends of the finger correspond to the Morse code letter S, and three large bends correspond to the Morse code letter O. By repeating the bending, distress signals such as SOS can be sent in a timely manner, as well as other information, such as "help me".

[0058] 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 preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing an anti-swelling self-adhesive hydrogel sensor based on multiple dynamic cross-linking, characterized in that: first, acrylic acid, hydroxyethyl methacrylate copolymer and cationic polymer chitosan quaternary ammonium salt are used as the network skeleton of the hydrogel to construct a double network structure; then, tannic acid that can improve the adhesion and mechanical properties of the gel material is added to prepare a precursor solution; finally, the precursor solution is photocured under ultraviolet light to obtain an anti-swelling self-adhesive hydrogel.

2. The method according to claim 1, characterized in that The method comprises the following specific steps: (1) Add acrylic acid, hydroxyethyl methacrylate, a chemical crosslinking agent, and a photoinitiator into deionized water and stir at room temperature until completely dissolved to prepare a solution 1; (2) adding a certain amount of cationic polymer chitosan quaternary ammonium salt and effective adhesion unit tannic acid to solution A and stirring evenly at room temperature to prepare solution 2; (3) Solution 2 is transferred to a reaction mold and placed under ultraviolet light to initiate polymerization, thereby obtaining a swelling-resistant self-adhesive hydrogel.

3. The method according to claim 1, characterized in that The mass ratio of acrylic acid: hydroxyethyl methacrylate: chemical crosslinking agent: photoinitiator: deionized water in the solution 1 of step (1) is 300:100:1:4:1000.

4. The method according to claim 1, characterized in that: The chemical cross-linking agent in step (1) is N'N-methylenebisacrylamide.

5. The method according to claim 1, characterized in that The photoinitiator described in step (1) is a free radical initiator, including photoinitiator I2959.

6. The method according to claim 1, characterized in that The mass ratio of chitosan quaternary ammonium salt to tannic acid in the solution 2 of step (2) is 0.1-0.5:0.2-0.

6.

7. The method according to claim 1, characterized in that The wavelength of the ultraviolet lamp in step (3) is 365 nm, the power is 20 W, and the irradiation time is 1 h.

8. An anti-swelling self-adhesive hydrogel sensor prepared by the method according to any one of claims 1 to 7.

9. Use of the anti-swelling self-adhesive hydrogel sensor as claimed in claim 5 in sensor materials.

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