Anti-swelling high-adhesion hydrogel strain sensor for underwater monitoring and preparation method thereof

Abstract

The invention belongs to the technical field of hydrogel strain sensors, and particularly relates to an anti-swelling high-adhesion hydrogel strain sensor for underwater monitoring and a preparation method of the anti-swelling high-adhesion hydrogel strain sensor. The hydrogel strain sensor comprises PAA / (SBMA-co-HEMA) / TA hydrogel, and the hydrogel is provided with a micron-sized uniform porous structure and a continuously interconnected void network. The underwater adhesion performance of the hydrogel is improved through multiple interactions between catechol groups of the TA and hydrogen bonds, coordinate bonds, covalent bonds and the like in polymer chains. Due to the introduction of HCl, the osmotic pressure of the hydrogel is reduced through electrostatic repulsion among cations, and the swelling resistance of the hydrogel is improved; and the ion transmission efficiency of the hydrogel can be improved by a large number of free particles, so that the conductivity of the hydrogel strain sensor is improved. The hydrogel strain sensor shows excellent sensing performance in water, and has huge application potential in the field of underwater information transmission.

Description

Technical Field

[0001] The present application relates to the technical field of hydrogel strain sensors, and in particular to an anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring and a preparation method thereof. Background Art

[0002] With the rapid development of flexible electronics and intelligent monitoring systems, hydrogel-based strain sensors have found widespread application in wearable devices, intelligent robotics, and environmental sensing due to their excellent flexibility, high biocompatibility, and good ionic conductivity. In particular, in underwater monitoring scenarios, highly adhesive, anti-swelling hydrogel strain sensors have garnered significant attention for their applications in underwater infrastructure energy equipment, underwater monitoring, and underwater robotics.

[0003] However, traditional hydrogel materials suffer from significant swelling issues. Due to their high water content and relatively weak internal cross-linking, water molecules continuously penetrate into the hydrogel when used in underwater environments, leading to network structure destruction, decreased mechanical properties, and poor adhesion in complex humid environments, further weakening the stability and reliability of the sensor.

[0004] To address these challenges, efforts have been made to improve the anti-swelling properties of hydrogels by constructing dual network structures and introducing hydrophobic groups. Furthermore, various reversible physical interactions are often introduced into the hydrogel system to enhance interfacial bonding strength and improve underwater adhesion stability. However, in the prior art, most hydrogel materials still suffer from complex preparation processes, difficulties in balancing adhesion and anti-swelling properties, insufficient mechanical properties, and easy degradation after prolonged underwater use, limiting their widespread application in practical underwater monitoring applications. Therefore, there is an urgent need to develop anti-swelling, highly adhesive hydrogel strain sensors for underwater monitoring and their preparation methods to address these issues. Summary of the Invention

[0005] In view of this, the present application provides an anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring and a preparation method thereof. The hydrogel strain sensor exhibits excellent anti-swelling and high adhesion in water, and has great application potential in the field of underwater information transmission.

[0006] Specifically, the following technical solutions are included: In a first aspect, embodiments of the present application provide an anti-swelling, high-adhesion hydrogel strain sensor for underwater monitoring, wherein the hydrogel strain sensor comprises a PAA / (SBMA-co-HEMA) / TA hydrogel, wherein the PAA / (SBMA-co-HEMA) / TA hydrogel has a micron-scale uniform porous structure and a continuously interconnected void network.

[0007] In some embodiments, the raw materials of the PAA / (SBMA-co-HEMA) / TA hydrogel include acrylic acid, methacryloylethyl sulfobetaine, hydroxyethyl methacrylate, and tannic acid.

[0008] In some embodiments, the raw materials of the PAA / (SBMA-co-HEMA) / TA hydrogel further include an ion regulator, and the ion regulator is hydrogen chloride.

[0009] In a second aspect, embodiments of the present application provide a method for preparing an anti-swelling, high-adhesion hydrogel strain sensor for underwater monitoring, the preparation method comprising: Acrylic acid, methacryloylethyl sulfobetaine, and hydroxyethyl methacrylate are dispersed in deionized water and mixed evenly, and then tannic acid, an ion regulator, an initiator, and a cross-linking agent are added. After mixing, the mixture is degassed and then polymerized to obtain a PAA / (SBMA-co-HEMA) / TA hydrogel, thereby obtaining the hydrogel strain sensor.

[0010] In some embodiments, the mixing mass ratio of acrylic acid, methacryloylethyl sulfobetaine, and hydroxyethyl methacrylate is (1.5-2):(1.5-2):(0-1).

[0011] In some embodiments, the mixing ratio of tannic acid, ion regulator, initiator and cross-linking agent is (0-1) g: (0-4) %: (0.01-0.02) g: (15-25) μL.

[0012] In some embodiments, the ion regulator is hydrogen chloride, the initiator is potassium persulfate, and the cross-linking agent is tetramethylethylenediamine.

[0013] In some embodiments, the polymerization reaction temperature is 55-65° C., and the reaction time is 4-6 hours.

[0014] In some embodiments, the tannic acid, ion regulator, initiator, and cross-linking agent are added and mixed with stirring for 0.5 to 1 hour.

[0015] In some embodiments, tannic acid, an ion regulator, an initiator, and a cross-linking agent are added and mixed, and then degassing is performed by ultrasonic treatment for 10 to 20 minutes.

[0016] The beneficial effects of the technical solutions provided by the embodiments of the present application include at least: The present invention provides an anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring and a preparation method thereof. The hydrogel strain sensor includes a PAA / (SBMA-co-HEMA) / TA hydrogel. The PAA / (SBMA-co-HEMA) / TA hydrogel has a micron-scale uniform porous structure and a continuously interconnected void network. TA is added to PAA and P(SBMA- co -HEMA) polymer network, catechol groups were introduced, and combined with an optimized anti-swelling strategy, an anti-swelling hydrogel with high adhesion ability was successfully prepared. The rich catechol groups in TA can achieve efficient adhesion to the substrate through various interactions such as hydrogen bonds, coordination bonds and covalent bonds in the polymer chain, effectively improving the underwater adhesion performance of the hydrogel. On the one hand, the introduction of HCl can regulate the ionic equilibrium state of the zwitterions, reduce the osmotic pressure of the hydrogel through the electrostatic repulsion between cations, and greatly improve the anti-swelling ability of the hydrogel; on the other hand, the large number of free particles brought about can improve the ion transmission efficiency of the hydrogel, thereby improving the conductive properties of the hydrogel strain sensor. The hydrogel strain sensor exhibits excellent sensing performance in water and has great application potential in the field of underwater information transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 Schematic diagram of the structure of the PAA / (SBMA-co-HEMA) / TA hydrogel in the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring provided in an embodiment of the present application; Figure 2 Characterization results of the PAA / (SBMA-co-HEMA) / TA hydrogel in the anti-swelling, high-adhesion hydrogel strain sensor for underwater monitoring provided in the embodiments of the present application: (a) FTIR characterization results, (b) XPS characterization results; Figure 3 SEM images of PAA / (SBMA-co-HEMA) / TA hydrogel in the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring provided in the embodiment of the present application: (a) PAB, (b) PAB M , (c) PAB M Low-magnification image of TH, (d) PAB M High-magnification image of TH; Figure 4Mechanical properties of hydrogels in the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring provided in the embodiments of this application: (a) tensile curves of hydrogels with different HCl contents, (b) tensile curves of hydrogels with different TA contents, (c) comparison of tensile properties of different hydrogels, (d) PAB M Tensile curves of TH hydrogel under different strains; Figure 5 The anti-swelling performance diagram of the hydrogel in the anti-swelling high-adhesion hydrogel strain sensor for underwater monitoring provided in the embodiment of this application: (a) The effect diagram of the hydrogel soaked in water for 20 days, (b) PAA, PAB M 、PAB M Water contact angle diagram of TH hydrogel, (c) PAB M SEM image of TH hydrogel before swelling, (d) PAB M SEM image of TH hydrogel after swelling; Figure 6 The swelling curve of the hydrogel in the anti-swelling high-adhesion hydrogel strain sensor for underwater monitoring provided in the embodiment of the present application: (a) the swelling curve of the hydrogel after being immersed in water for 20 days, (b) the swelling curve of the PAB M Swelling curves of TH hydrogel in different solutions, (c) PAB M Swelling ratio of TH hydrogel in different solutions; Figure 7 Schematic diagram of the adhesion effect of PAA / (SBMA-co-HEMA) / TA hydrogel in the anti-swelling, high-adhesion hydrogel strain sensor for underwater monitoring provided in the embodiments of the present application: (a) schematic diagram of adhesion in water, (b) schematic diagram of close adhesion to different substrate surfaces in water; Figure 8 Adhesion peeling curve and adhesion strength of the hydrogel in the anti-swelling high-adhesion hydrogel strain sensor for underwater monitoring provided by the embodiment of the present application: PAB with different TA contents M (a) Adhesion-peeling curve and (b) adhesion strength of TH hydrogel, PAB, PAB M 、PAB M -H, PAB M (c) Adhesion-peel curves and (d) adhesion strength of TH hydrogels. Figure 9 For the anti-swelling, high-adhesion hydrogel strain sensor for underwater monitoring provided in an embodiment of the present application, (a) the sensitivity of the hydrogel sensor, (b) the response recovery time of the hydrogel sensor, (c) the response of the sensor to small strain, and (d) the response of the sensor to large strain; Figure 10This is a test result diagram of the long-term stability of the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring provided in an embodiment of the present application; Figure 11 Schematic diagram of the operation of the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring provided in an embodiment of the present application for underwater information transmission; Figure 12 A characteristic diagram of the Morse code transmitted by the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring provided in an embodiment of the present application; Figure 13 This is a diagram showing the effect of the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring provided in an embodiment of the present application transmitting information underwater. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0020] In order to make the technical solutions and advantages of the present application clearer, the implementation methods of the present application will be described in further detail below with reference to the accompanying drawings.

[0021] In the first aspect, the embodiments of the present application provide an anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring, such as Figure 1 As shown, the hydrogel strain sensor includes PAA / (SBMA-co-HEMA) / TA hydrogel, which has a micron-scale uniform porous structure and a continuously interconnected void network to provide ion transmission channels.

[0022] In some embodiments, the raw materials of the PAA / (SBMA-co-HEMA) / TA hydrogel include acrylic acid, methacryloylethyl sulfobetaine, hydroxyethyl methacrylate, and tannic acid.

[0023] In some embodiments, the raw materials of the PAA / (SBMA-co-HEMA) / TA hydrogel further include an ion regulator, and the ion regulator is hydrogen chloride.

[0024] In summary, the present invention provides an anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring, wherein TA is added to PAA and P(SBMA- co-HEMA) polymer network, catechol groups were introduced, and combined with an optimized anti-swelling strategy, an anti-swelling hydrogel with high adhesion ability was successfully prepared. The rich catechol groups in TA can achieve efficient adhesion to the substrate through various interactions such as hydrogen bonds, coordination bonds and covalent bonds in the polymer chain, effectively improving the underwater adhesion performance of the hydrogel. On the one hand, the introduction of HCl can regulate the ionic equilibrium state of the zwitterions, reduce the osmotic pressure of the hydrogel through the electrostatic repulsion between cations, and greatly improve the anti-swelling ability of the hydrogel; on the other hand, the large number of free particles brought about can improve the ion transmission efficiency of the hydrogel, thereby improving the conductive properties of the hydrogel strain sensor. The hydrogel strain sensor exhibits excellent sensing performance in water and has great application potential in the field of underwater information transmission.

[0025] In a second aspect, an embodiment of the present application provides a method for preparing an anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring, the preparation method comprising: Acrylic acid, methacryloylethyl sulfobetaine, and hydroxyethyl methacrylate were dispersed in deionized water and mixed evenly. Tannic acid, an ion regulator, an initiator, and a cross-linking agent were then added. After mixing, the mixture was degassed and polymerized to obtain PAA / (SBMA-co-HEMA) / TA hydrogel, thereby obtaining a hydrogel strain sensor.

[0026] In some embodiments, the mixing mass ratio of acrylic acid, methacryloylethyl sulfobetaine, and hydroxyethyl methacrylate is (1.5-2):(1.5-2):(0-1).

[0027] In some embodiments, the mixing ratio of tannic acid, ion regulator, initiator and cross-linking agent is (0-1) g: (0-4) %: (0.01-0.02) g: (15-25) μL.

[0028] In some embodiments, the ion regulator is hydrogen chloride, the initiator is potassium persulfate, and the cross-linking agent is tetramethylethylenediamine.

[0029] In some embodiments, the polymerization reaction temperature is 55-65° C., and the reaction time is 4-6 hours.

[0030] In some embodiments, the tannic acid, ion regulator, initiator, and cross-linking agent are added and mixed with stirring for 0.5 to 1 hour.

[0031] In some embodiments, tannic acid, an ion regulator, an initiator, and a cross-linking agent are added and mixed, and then degassing is performed by ultrasonic treatment for 10 to 20 minutes.

[0032] In some embodiments, PAA / (SBMA-co-HEMA) / TA hydrogel was prepared by a one-pot method. First, 1.72 g AA, 1.68 g SBMA, and 0.6 g HEMA were added to 8 g deionized water and mixed evenly. Then 3 wt% HCl, 0.07 g TA, 20 μL tetramethylethylenediamine (TEMED), and 0.015 g potassium persulfate (KPS) were added to the mixed solution and stirred for 0.5 h to fully mix all the components. HCl was used to induce the protonation of SBMA. Under the action of KPS and TEMED, HEMA and the protonated SBMA monomers copolymerized. The mixed solution was ultrasonically treated for 10 min to remove bubbles. Finally, the mixed solution was poured into a silicone mold and heated at 60 o The PAA / (SBMA-co-HEMA) / TA hydrogel was polymerized at 4 °C for 4 h. The hydrogel was then assembled into a flexible tactile sensor using the hydrogel as the sensing layer, a flexible electrode as the electrode layer, and PDMS as the flexible shielding layer, thereby obtaining a hydrogel strain sensor.

[0033] PAA / (SBMA-co-HEMA) / TA hydrogels without HCl, TA and HEMA, without TA, HCl and without TA were prepared by the same method and named as PAB, PAB M 、PAB M -H. To confirm PAB M The formation of TH hydrogel (abbreviation of PAA / (SBMA-co-HEMA) / TA hydrogel) was carried out, and the hydrogel was characterized by FTIR and XPS, as shown in Figure 5. Figure 2 (a) and Figure 2 As shown in (b), by comparing the four hydrogels, the stretching vibration peak of OH in the hydroxyl group of PAB hydrogel is from 3436 cm -1 Move to PAB M 3432 cm of hydrogel -1 This indicates the formation of a large number of hydrogen bonds, while in PAB M -H and PAB M In the FTIR spectrum of TH hydrogel, the stretching vibration frequencies of these two locations shifted to lower wavenumbers, indicating that the hydrogen bonds were strengthened. The C=O stretching vibration peak in the ester group of PAB hydrogel shifted from 1738 cm -1 Move to PAB M 1733 cm of TH hydrogel -1 In addition, a peak at 1154 cm was observed in the PAB spectrum. -1 and 1035 cm -1 The two characteristic peaks at are due to the symmetric stretching vibration and asymmetric stretching vibration of the S=O bond.M -H and PAB M TH hydrogel at 1033 cm -1 The characteristic absorption peak of the sulfonic acid group at the position of the sulfonic acid group was weakened, which also confirmed the protonation of the sulfonic acid group. The XPS spectra of elements such as C, N, O, and S in the three hydrogels were compared. Figure 2 (b)

[0034] like Figure 3 (a) to Figure 3 (d) shows the microstructure of the hydrogel characterized by scanning electron microscopy. Compared with PAB hydrogel, PAB M The porous structure of the hydrogel still exists after the addition of HEMA, but the pore size of the hydrogel becomes smaller and the pore structure becomes irregular. The introduction of HEMA enhances the hydrogen bonding and hydrophobic interactions between the chain segments, thereby increasing the cross-linking density of the network. M The TH hydrogel exhibits an increased number of pores but a significant decrease in pore size, forming a honeycomb-like microporous structure with a continuous, interconnected pore network that provides pathways for ion transport. The introduction of TA provides a large number of phenolic hydroxyl groups, which can form multi-point dynamic crosslinks with the hydrogel network through hydrogen bonds, significantly enhancing the stability and uniformity of the hydrogel network.

[0035] Hydrogels with different TA and HCl contents were prepared using the same method and were labeled as PAB. M T y -H x , x is the mass fraction of HCl, y is the mass of TA. The effects of different contents of HCl and TA on the mechanical properties of hydrogels were tested by tensile tests. Figure 4 As shown in (a), as the mass fraction of HCl increases from 0 wt% to 3 wt%, the elongation at break of the hydrogel increases continuously. This is because the introduction of HCl causes the negatively charged -SO3 - The groups are transformed into -SO3H groups, providing more hydrogen bonds and improving the mechanical properties of the hydrogel. However, as the HCl content continues to increase, the elongation at break of the hydrogel decreases. This is because the excessive hydrogen bonds and the formation of regular and ordered structures induced by excessive hydrochloric acid stimulate the "hardening effect", which in turn reduces the mechanical properties of the hydrogel. Figure 4 As shown in (b), the stretchability of the hydrogel increases with the increase of TA content. This is because the introduction of TA brings more hydrogen bonds, which significantly improves the tensile properties of the hydrogel. However, excessive TA will cause the tensile strength of the hydrogel to gradually decrease, which is attributed to excessive cross-linking and uneven phase separation at high TA concentrations. Therefore, in subsequent tests, PAB with excellent performance was selected. M T 0.07 -H3 hydrogel as a representative, with PABM TH indicates. Figure 4 (c) shows PAB M The TH hydrogel achieved a high tensile strength of 81.84 kPa and did not break at a strain of 2025%. Figure 4 (d) shows the continuous loading-unloading curves of the hydrogel at different strain levels. As can be seen, the hysteresis curve gradually increases as the strain increases from 100% to 600%. This increase in hysteresis reflects an increase in dissipated energy. In contrast, at lower strains, the dissipated energy is smaller. This is because during the unloading phase, the polymer chains of the hydrogel rearrange themselves, tending to restore their original structure and morphology. Simultaneously, some broken hydrogen bonds are re-established, a process that promotes the hydrogel's self-healing ability.

[0036] Anti-swelling property is a key factor for the application of hydrogel strain sensors in underwater environments. Therefore, PAB was tested. M Swelling behavior of TH hydrogel in deionized water and artificial seawater. Figure 5 As shown in (a), whether it is deionized water or artificial seawater, the hydrogel shows obvious anti-swelling behavior and the volume change is very small. M Compared with hydrogel, PAB M TH hydrogel has a low water contact angle such as Figure 5 (b) shows excellent hydrophobic properties. The introduction of HEMA forms a tighter network structure with SBMA, while HCl protonates the sulfonate groups in SBMA to form a polycationic electrolyte hydrogel. The electrostatic repulsion between cations reduces the osmotic pressure of the hydrogel, thereby reducing the swelling rate of the hydrogel. PAB was determined by SEM. M The microstructure of TH hydrogel before and after swelling, such as Figure 5 As shown in (c) and 5 (d), the network structure of the hydrogel did not collapse after swelling when immersed in deionized water, which indicates that the hydrogel has ideal anti-swelling properties.

[0037] The hydrogel was immersed in water and the swelling kinetics curve of the hydrogel was determined by measuring the swelling rate of the hydrogel after it absorbed water. Figure 6 (a) and Figure 6 (b) It can be seen that PAA and PAB M After being immersed in deionized water for one day, the swelling rate of the hydrogel increased rapidly, and finally reached equilibrium swelling rates of 327% and 51%, respectively. M The equilibrium swelling ratio of TH hydrogel after immersion in deionized water for 20 days was only 9%. M Swelling behavior of TH hydrogel in different solvents. Figure 6 As shown in (c), the equilibrium swelling rate of the hydrogel in artificial seawater is slightly higher than that in pure water. This is because the surface charge of the hydrogel is shielded by the small molecule electrolyte salt in the electrolyte solution, which enhances the hydration of the zwitterions and promotes penetration and swelling. M TH hydrogel maintains good anti-swelling behavior in acidic and neutral solutions. As the pH of the solution increases, the swelling rate gradually increases. However, even when the pH increases to 10, the equilibrium swelling rate is less than 70%. In an acidic environment, -SO3 - The groups are protonated, making the hydrogel behave like a polycation. However, in an alkaline environment, alkaline ions induce anti-polyelectrolyte effects and dissociation within and between PSBMA chains, which increases the swelling rate of the hydrogel. M The excellent anti-swelling property of TH provides the necessary guarantee for its use as a hydrogel strain sensor for underwater sensing.

[0038] Flexible tactile sensors based on hydrogels need to contact the human body / robot surface, so reliable adhesion is crucial. Schematic diagram of hydrogel underwater adhesion test Figure 7 (a) shows PAB M TH hydrogels can adhere tightly to the surfaces of various materials with different shapes, such as Figure 7 As shown in (b), various materials with different shapes including glass, wood, silicone, metal and ceramics, the hydrogel can adhere to and lift objects underwater without falling off, which shows that the hydrogel can be widely used in a variety of substrates. M Adhesion strength of TH hydrogel to different substrates, PAB M The TH hydrogel was subjected to lap shear test with the substrate. The effect of different TA contents on the adhesion of the hydrogel was first tested, and PAB with different TA contents was prepared. M TH hydrogel. Figure 8 (a) and Figure 8 As shown in (b), as the TA content increases, the adhesion strength of the hydrogel to the wood gradually increases, which indicates that the hydrogel has adjustable adhesion strength. Inspired by mussels, by introducing catechol groups into the hydrogel system, a large number of catechol groups on TA can achieve efficient adhesion to the substrate through various interactions such as hydrogen bonds, coordination bonds and covalent bonds, and form a cross-linked network with anti-swelling ability under certain conditions. Figure 8 (c) and Figure 8 (d) It can be seen that PAB M TH hydrogel exhibits excellent adhesion properties, which helps the hydrogel strain sensor to be firmly attached to the detection site, thereby improving the accuracy and real-time performance of underwater sensing.

[0039] When hydrogel is used in underwater flexible sensors, its sensing performance is a very important factor. M TH hydrogels exhibit excellent underwater sensing performance. When conductive hydrogels are stimulated by external stimuli, the shape or size of the hydrogels changes, causing changes in the internal network and conductive pathways of the hydrogels, affecting the ion migration behavior in the hydrogels, and ultimately causing changes in electrical signals. The zwitterionic hydrogel polymer chain contains positively charged -R3N + Group and negatively charged -SO3 - Groups, these zwitterionic side groups form ordered ion migration channels under the action of an external electric field. The introduction of HCl increases the number of free particles, improves the ion transmission efficiency of the hydrogel, and greatly improves the conductive properties of the hydrogel strain sensor. In order to evaluate the conductive properties of the hydrogel, the sensitivity coefficient (GF) of the hydrogel was measured. Figure 9 As shown in (a), GF gradually increases in the three strain ranges and reaches a maximum value of 2.09 when the strain range is 400~600%. The hydrogel strain sensor shows a very fast response to external stimuli, such as Figure 9 As shown in (b), when the sensor is stretched (50%) instantaneously, the response time is 360 ms. After the strain is unloaded, the sensor returns to its initial state in 420 ms. Figure 9 (c) and Figure 9 As shown in (d), whether the tensile test is carried out in a small strain range (1%, 3%, 6% and 10%) or a large strain range (100%, 200%, 300% and 400%), the hydrogel strain sensor shows stable, fast and easy-to-distinguish electrical signal response characteristics, which fully proves that the sensor has excellent strain resolution and good repeatability. Most importantly, the sensor shows a detection limit as low as 1%, which shows the application capability of the sensor in sensing tiny signals. In addition, the sensing durability of the hydrogel strain sensor was tested, as shown in Figure 2. Figure 10 As shown, the response change of the hydrogel in the cyclic test under 50% strain remained relatively stable, indicating that the hydrogel strain sensor has excellent durability and long-term stability.

[0040] With the continuous development of marine resources, underwater information transmission has received more and more attention. Due to the complexity and danger of underwater operations, in order to ensure the safety and efficiency of underwater operations, there is an increasing demand for portable and flexible communication equipment that can be used underwater. M TH hydrogels have excellent anti-swelling and sensing properties, such as Figure 11As shown, a hydrogel strain sensor attached to a finger can achieve underwater communication based on the principle of Morse code. When the finger is bent at an angle less than 60°, the peak of the sensor's output signal corresponds to the "." in Morse code. When the finger is bent at approximately 90°, the output signal represents the "-" in the sensor. Through regular bending patterns, the hydrogel strain sensor can transmit information.

[0041] like Figure 12 It can be seen that by comparing the characteristic signals of different Morse codes, the hydrogel strain sensor can clearly show the different responses of the 26 English letters. The underwater communication capability of the hydrogel strain sensor was verified. When people are diving or working underwater, people wearing the hydrogel strain sensor can send information simply and quickly by regularly bending their fingers, such as Figure 13 As shown in the figure, for example, "SOS" and "Help" can be sent out when in danger, or a series of short messages such as "OK" can be sent out when working underwater. Combining hydrogel strain sensors with Morse code provides a simple, reliable, and energy-efficient method for underwater communication. With the continuous development of deep learning and intelligent sensing technology, it has broad application prospects in underwater resource detection, military and rescue.

[0042] In summary, the present invention provides a method for preparing a high-adhesion hydrogel strain sensor for underwater monitoring by adding TA to PAA and P(SBMA- co -HEMA) polymer network, catechol groups were introduced, and combined with an optimized anti-swelling strategy, an anti-swelling hydrogel with high adhesion ability was successfully prepared. The rich catechol groups in TA can achieve efficient adhesion to the substrate through various interactions such as hydrogen bonds, coordination bonds and covalent bonds in the polymer chain, effectively improving the underwater adhesion performance of the hydrogel. On the one hand, the introduction of HCl can regulate the ionic equilibrium state of the zwitterions, reduce the osmotic pressure of the hydrogel through the electrostatic repulsion between cations, and greatly improve the anti-swelling ability of the hydrogel; on the other hand, the large number of free particles brought about can improve the ion transmission efficiency of the hydrogel, thereby improving the conductive properties of the hydrogel strain sensor. The hydrogel strain sensor exhibits excellent sensing performance in water and has great application potential in the field of underwater information transmission.

[0043] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. The term "plurality" refers to two or more than two, unless expressly limited otherwise.

[0044] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the present invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only.

[0045] It should be understood that the present application is not limited to the exact structure described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. Anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring, characterized in that: The hydrogel strain sensor includes PAA / (SBMA-co-HEMA) / TA hydrogel, and the PAA / (SBMA-co-HEMA) / TA hydrogel has a micron-scale uniform porous structure and a continuously interconnected void network.

2. The anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring according to claim 1, characterized in that: The raw materials of the PAA / (SBMA-co-HEMA) / TA hydrogel include acrylic acid, methacryloylethyl sulfobetaine, hydroxyethyl methacrylate and tannic acid.

3. The anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring according to claim 1, characterized in that: The raw materials of the PAA / (SBMA-co-HEMA) / TA hydrogel include an ion regulator, and the ion regulator is hydrogen chloride.

4. A method for preparing a swelling-resistant and highly adhesive hydrogel strain sensor for underwater monitoring, characterized in that: The preparation method comprises: Acrylic acid, methacryloylethyl sulfobetaine, and hydroxyethyl methacrylate are dispersed in deionized water and mixed evenly, and then tannic acid, an ion regulator, an initiator, and a cross-linking agent are added. After mixing, the mixture is degassed and then polymerized to obtain a PAA / (SBMA-co-HEMA) / TA hydrogel, thereby obtaining the hydrogel strain sensor.

5. The method for preparing the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring according to claim 4, characterized in that: The mixing mass ratio of acrylic acid, methacryloylethyl sulfobetaine and hydroxyethyl methacrylate is (1.5~2):(1.5~2):(0~1).

6. The method for preparing the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring according to claim 4, characterized in that: The mixing ratio of tannic acid, ion regulator, initiator and cross-linking agent is (0~1)g: (0~4)%: (0.01~0.02)g: (15~25)μL.

7. The method for preparing the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring according to claim 4, characterized in that: The ion regulator is hydrogen chloride, the initiator is potassium persulfate, and the cross-linking agent is tetramethylethylenediamine.

8. The method for preparing the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring according to claim 4, characterized in that: The polymerization temperature is 55~65℃, and the reaction time is 4~6 h.

9. The method for preparing the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring according to claim 4, characterized in that: When adding tannic acid, ion regulator, initiator and cross-linking agent and mixing, stir for 0.5 to 1 hour.

10. The method for preparing the anti-swelling and high-adhesion hydrogel strain sensor for underwater monitoring according to claim 4, characterized in that: After adding tannic acid, ion regulator, initiator and cross-linking agent, the mixture was degassed by ultrasonic treatment for 10 to 20 minutes.

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