Anti-swelling hydrogel strain sensor, preparation method and visual touch fusion sensing system

Abstract

The present application belongs to the technical field of intelligent soft materials, and particularly relates to an anti-swelling hydrogel strain sensor, a preparation method and a visual touch fusion sensing system. The present application constructs an anti-swelling and high-stability hydrogel PABMS with high sensitivity under water through MXene and sodium alginate (SA) in cooperation with acrylic acid (AA) and methacryloyl ethyl sulfobetaine (SBMA). The sensor applying the hydrogel can maintain stable sensing performance in an underwater environment, has a fast tactile response capability, can be applied to water wave vibration monitoring and tactile signal sensing, and has a wide application prospect in underwater robots, underwater detection, human-computer interaction and other fields.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of intelligent soft materials, and particularly relates to an anti-swelling hydrogel strain sensor, a preparation method and a visual touch fusion sensing system. BACKGROUND

[0002] Hydrogels have wide application potential in underwater detection, environmental monitoring, biomedical and underwater sensing due to their excellent electrical conductivity, adjustable mechanical properties and good biocompatibility. However, the swelling characteristics of hydrogels cause the change of the structure of hydrogels to destroy the stability of the ion conduction channel, thereby causing distortion of the sensing signal, and even making the sensor unable to work normally. Moreover, the existence of concentration gradient in water causes the diffusion of the conductive components of the hydrogel through the cross interface, which eventually leads to the decline of the electrical properties, affecting the sensing accuracy and service life, which becomes the main bottleneck restricting the underwater application of hydrogel tactile sensors. How to effectively inhibit the swelling of hydrogels and improve their electrical conductivity is an important challenge in the field of hydrogels at present. Therefore, it is of important research significance and application value to develop a hydrogel material with anti-swelling, high sensitivity and stable underwater sensing performance.

[0003] By introducing some hydrophobic nanomaterials, the electrical conductivity and swelling behavior of hydrogels can be effectively adjusted. In recent years, two-dimensional layered materials have attracted widespread attention in the field of flexible electronics and sensors due to their excellent mechanical, electrical and hydrophobicity regulation properties. Among them, MXene, as a new type of two-dimensional nanomaterial, has become a popular choice for enhancing the electrical conductivity of hydrogels due to its excellent electrical conductivity and rich surface functional groups.

[0004] Therefore, how to provide an anti-swelling high-sensitivity hydrogel sensor based on MXene composite hydrogel material is a technical problem that those skilled in the art need to solve urgently. SUMMARY

[0005] In view of the problem that the above-mentioned hydrogel causes the decline of sensing ability after swelling in water, the application constructs a high-sensitivity anti-swelling hydrogel PABMS by synergizing MXene and sodium alginate (SA) with acrylic acid (AA) and methacryloyl ethyl sulfobetaine (SBMA).

[0006] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0007] A preparation method of an anti-swelling hydrogel strain sensor, comprising the following steps:

[0008] (1) SA is added to the MXene solution, and stirred until completely dissolved to obtain a mixed solution I;

[0009] (2) Then AA, SBMA, crosslinking agent, initiator are added to the mixed solution I, and the mixed solution II is obtained after stirring uniformly;

[0010] (3) The mixed solution II is degassed in vacuum, and the anti-swelling hydrogel hydrogel is obtained by in-situ polymerization at 55-65 DEG C.

[0011] (4) The anti-swelling hydrogel is assembled into a flexible tactile sensor as a sensing layer.

[0012] Preferably, the MXene solution is a Ti3C2Tx MXene nanosheet solution synthesized by selectively etching aluminum elements in Ti3AlC2 using a mixed solution of LiF and HCl.

[0013] Preferably, the preparation method of the MXene solution is as follows: 1.5-2g of LiF is weighed and added into 30ml of HCl solution and stirred for 5-10min in a 30-35 DEG C water bath environment; then 2-2.5g of carbon titanium aluminum powder is added into the above solution under stirring for 5-8min at 30-35 DEG C; continuous stirring is carried out for 30-35h to ensure that the reaction is completed; the reacted solution is taken out, washed with deionized water, and then centrifuged until no supernatant is generated, and the pH of the solution is greater than 6; the obtained solution is ultrasonically treated for 0.5-1h, the temperature is kept below 35 DEG C, and then centrifuged at 3000-3500r·min -1 for 5-8min to obtain the MXene solution.

[0014] Preferably, the mass ratio of SA, MXene solution, AA, SBMA is (0.1-0.3):(8-10):(1.5-5):(1.5-2); the concentration of the MXene solution is 1-3wt%. More preferably, the mass ratio of SA, MXene solution, AA, SBMA is (0.2-0.3):10:1.72:1.68; the concentration of the MXene solution is 2-3wt%. Most preferably, the mass ratio of SA, MXene solution, AA, SBMA is 0.3:10:1.72:1.68; the concentration of the MXene solution is 3wt%.

[0015] Preferably, the crosslinking agent is an MBAA solution, the initiator is an AIBI solution, the concentration of the crosslinking agent is 1wt%, the concentration of the AIBI solution is 10wt%, and the mass-volume ratio of the MXene solution, the MBAA solution and the AIBI solution is 10:(180-200)ul:(160-180)ul.

[0016] The anti-swelling hydrogel strain sensor prepared by the above preparation method is required to be protected

[0017] Preferably, the strain sensor is an underwater flexible tactile strain sensor.

[0018] Preferably, the anti-swelling hydrogel described above is assembled into a flexible tactile sensor as a sensing layer, and polydimethylsiloxane is used as a flexible shielding layer.

[0019] The application also discloses a visual and tactile fusion perception system, which comprises a visual recognition and positioning system, a tactile signal acquisition system, a signal processing unit and a system software interface; the strain sensor described above is a sensing unit of the tactile signal acquisition system.

[0020] Compared with the prior art, the application has the following beneficial effects:

[0021] The application adopts a nano-filling enhancement strategy. The introduction of MXene not only provides more conductive channels through its high surface area, but also interacts with the molecules in the hydrogel through the functional groups contained on its surface, which helps to regulate the swelling behavior of the hydrogel and improve the structural stability of the hydrogel in underwater environment. Based on the hydrogel, the application designs a hydrogel flexible tactile sensor with high stability and high sensitivity through structural assembly design, and systematically studies its multifunctional application in underwater environment. The sensor can maintain stable sensing performance in underwater environment, has fast tactile response capability, can be applied to water wave vibration monitoring and tactile signal perception, and has wide application prospect in underwater robots, underwater detection, human-computer interaction and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic diagram of the preparation of PABMS hydrogel in Example 1. Figure 1 Figure 2 is an infrared spectrum of PAA, PAB, SBMA and PABMS hydrogels in Example 1.

[0023] Figure 3 is a SEM image of different hydrogels in Example 1.(a) MXene; (b) PAB; (c) low magnification and (d) high magnification of PABMS. Figure 2 Figure 4 is an element distribution diagram of C, O, S and the like in PABMS hydrogel in Example 1.

[0024] Figure 3 Figure 5 is a diagram of the preparation of PABMS hydrogel in Example 2.

[0025] Figure 6 is an infrared spectrum of PABMS hydrogel in Example 2. Figure 4 Figure 7 is a SEM image of PABMS hydrogel in Example 2.

[0026] Figure 5 Figure 8 is an element distribution diagram of C, O, S and the like in PABMS hydrogel in Example 2. x S y ​​Mechanical properties of hydrogels; (a) Compression test of hydrogels with different MXene contents; (b) Maximum stress of hydrogels with different MXene contents; (c) Compression test of hydrogels with different SA contents; (d) Maximum stress of hydrogels with different SA contents; (e) Compression performance test of PAA, PAB, PABM, and PABMS hydrogels; (f) Maximum stress of PAA, PAB, PABM, and PABMS hydrogels;

[0027] Appendix Figure 6 PABM in Example 1 x S y Compressive strain properties of hydrogels; (a) Load-unloading curves at different compressive strains; (b) Maximum stress and dissipated energy at different compressive strains; (c) Cyclic load-unloading curves at 60% compressive strain; (d) Maximum stress and dissipation capacity under cyclic compression;

[0028] Appendix Figure 7 The following figures illustrate the anti-swelling properties of PAA, PABM, and PABMS hydrogels in Example 1: (a) Water contact angle of PAB and PABM hydrogels; (b) SEM image of PABMS hydrogel before swelling; (c) SEM image of PABMS hydrogel after swelling; (d) Swelling curve of the hydrogel; (e) Equilibrium swelling rate of the hydrogel.

[0029] Appendix Figure 8 The following are the adhesion performance diagrams of the PABMS hydrogel in Example 1: (a) Schematic diagram of hydrogel adhesion to different substrates; (b) Adhesion strength between hydrogel and different substrates; (c) Repeated adhesion strength of hydrogel.

[0030] Appendix Figure 9 This is a schematic diagram of the PABMS hydrogel flexible tactile sensor structure in Example 2;

[0031] Appendix Figure 10 The sensitivity performance of the flexible tactile sensor in Example 2 is as follows: (a) Comparison of the sensitivity of different hydrogel sensors; (b) Sensitivity of the PABMS hydrogel sensor; (c) Response of PABMS hydrogel under different stresses; (d) Response of PABMS hydrogel under different deformations.

[0032] Appendix Figure 11 The response recovery performance of the PABMS hydrogel sensor in Example 2 is shown below: (a) Response recovery time of the sensor; (b) IV curves under different pressures; (c) Response at different bending angles; (d) Response under stepped strain.

[0033] Appendix Figure 12The following are the sensing performance of the PABMS hydrogel sensor in Example 2 under different underwater depth conditions: (a) Schematic diagram of underwater depth sensing test of sensor; (b) Sensing test of sensor at 0cm from liquid surface; (c) Sensing test of sensor at 2cm from liquid surface; (d) Sensing test of sensor at 4cm from liquid surface; (e) Sensing test of sensor at 6cm from liquid surface.

[0034] Appendix Figure 13 The PABMS hydrogel sensor in Example 2 is shown to sense the surrounding water wave environment; (a) Schematic diagram of the sensor's sensing of water wave vibration; (b) Vibration response of a marble falling from different heights; (c) Vibration response of a marble repeatedly colliding with a tabletop.

[0035] Appendix Figure 14 The following are the signal responses of the PABMS hydrogel sensor in Example 2 to sensing minute mechanical vibrations on the liquid surface: (a) the response of the underwater sensor to sensing running stimulation; (b) the response of the underwater sensor to receiving different frequencies of impact on the ground; (c) the response of the underwater sensor to sensing a fishhook entering the water; and (d) the response of the underwater sensor to sensing a water bottle, branch, or stone entering the water.

[0036] Figure 15 The following are the sensing responses of the PABMS hydrogel sensor in Example 2 to objects of different shapes: (a) pressure response of a weight placed on the tactile sensor array; (b) pressure response of a rod-shaped weight placed on the tactile sensor array; (c) pressure response of a triangular weight placed on the tactile sensor array.

[0037] Figure 16 The PABMS hydrogel tactile sensor in Example 2 responds to pressure when writing different letters; (a) "U"; (b) "P"; (c) "C";

[0038] Figure 17 The dynamic trajectory capture characteristics of the PABMS hydrogel tactile sensor in Example 2; (a) Schematic diagram of writing the letter "Z"; (b) Multi-channel output signal of the sensor;

[0039] Figure 18 For the object shape recognition and detection of the mechanical gripper actuator in Example 2; (a) Schematic diagram of the integration of tactile sensor and mechanical gripper; (b) Image of the object used for gripping test; (c) Gripping test image; (d) Schematic diagram of tactile sensor used for object shape recognition and classification; (e) Multi-channel output signal of triangular prism; (f) Pressure mapping diagram of triangular prism;

[0040] Figure 19 This is a block diagram of the overall design of the visual-touch fusion sensing system in Example 3;

[0041] Figure 20This is a schematic diagram of the grasping force signal acquisition system in the visual-touch fusion sensing system of Example 3;

[0042] Figure 21 This is an example of the gripping force of the tactile signal acquisition system on different objects in the visual-tactile fusion perception system of Example 3. Detailed Implementation

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] The preparation of PAA / SBMA / MXene / SA anti-swelling hydrogel includes the following steps:

[0046] MXene solution preparation:

[0047] First, aluminum is selectively etched from the MAX phase material (Ti3AlC2) to synthesize Ti3C2T. x MXene nanosheets.

[0048] In a 35℃ water bath environment, weigh 2g of LiF and add it to 30mL of HCl solution, stirring for 10min. Then, add 2g of aluminum carbide powder to the above solution while stirring over 5min. Continue stirring the solution at 35℃ for 30h to ensure the reaction is complete. After the reaction, remove the solution and thoroughly wash the mixture with deionized water, then centrifuge until no supernatant is produced. At this point, the pH of the solution is greater than 6. Sonicate the resulting solution for 1h, maintaining the temperature below 35℃, then centrifuge at 3500 rpm. -1 Centrifuge for 5 minutes to obtain the prepared MXene solution.

[0049] PAA / SBMA / MXene / SA hydrogels were synthesized using a one-pot method, such as Figure 1 As shown.

[0050] 0.3 g SA was added to 10 g MXene solution, and the mixture was stirred vigorously until completely dissolved. Then, 1.72 g AA, 1.68 g SBMA, 200 μL of N,N-methylenebisacrylamide (MBAA) solution (1 wt%), and 180 μL of azobisisobutyrazoline hydrochloride (AIBI) solution (10 wt%) were added to the mixture. The solution was stirred continuously for 40 min. Finally, the resulting solution was degassed in vacuum for 5 h and polymerized in situ at 60 °C to obtain the desired hydrogel.

[0051] Different concentrations of MXene solutions (0, 1, 2, 3, and 4 wt%) were prepared using deionized water and MXene solution to investigate the effect of MXene content on hydrogel properties. Different amounts of SA (0, 0.1, 0.2, 0.3, and 0.4 g) were added under the same experimental conditions to investigate the effect of SA content on hydrogel properties. Finally, PABMxSy hydrogels were obtained, where x represents the MXene solution concentration and y represents the mass of added SA, x = 0, 1, 2, 3, 4, and y = 0, 0.1, 0.2, 0.3, 0.4. PABM3S3 hydrogels are abbreviated as PABMS.

[0052] Characterization of PAA / SBMA / MXene / SA hydrogel

[0053] 1. Infrared analysis

[0054] First, the chemical structure and composition of PAB, PAA, SBMA, and PABMS hydrogels were characterized by FTIR. Figure 2 ). SBMA's 1178cm -1 and 1042cm -1 The two absorption peaks at the specified location are generated by the symmetric and asymmetric stretching vibrations of the S=O group in the sulfonate group, respectively. In PAB and PABMS hydrogels, the corresponding peaks shifted to 1166 cm⁻¹. -1 and 1038cm -1 This indicates that SBMA was successfully incorporated into the hydrogel network. At 1723 cm⁻¹ -1 The absorption peaks around the left and right are attributed to the stretching vibrations of the carbonyl (C=O) group, which are mainly related to the ester functional group in SBMA and the carboxyl group in SA. A stretching vibration peak of the OH bond in the hydroxyl group was observed at 3459 cm⁻¹ in the infrared spectrum of PAA hydrogel. -1 At 3446 cm⁻¹, PAB and PABMS hydrogels showed a broader hydroxyl peak, which shifted to 3446 cm⁻¹. -1 This indicates that the introduction of SBMA and MXene formed a large number of hydrogen bonds.

[0055] 2SEM analysis

[0056] The microstructure of MXene, PAB, and PABMS hydrogels was further observed using scanning electron microscopy. The microstructure of the prepared MXene exhibited a clearly ordered layered structure. Figure 3 (a)). As shown in Figure (b) and Figure 3 As shown in (c), compared with PAB hydrogel, with the introduction of MXene and SA, PABMS hydrogel exhibits a denser mesh structure, smaller pore size, and more uneven porosity. Figure 3(d) This is because MXene has a large layered structure and specific surface area, which can enhance the structural stability of the hydrogel through the cross-linking mechanism in the hydrogel network. The abundant carboxylic acid groups in SA increase the interaction between polymer chains and promote the entanglement between polymer chains.

[0057] 3-element analysis

[0058] Figure 4 The EDS diagram of the main elements in the PABMS hydrogel is shown. It can be observed that elements such as N, O, S, and Ti are successfully doped into the hydrogel and are uniformly distributed. This indicates the effective synthesis of monomers such as SBMA and MXene in the hydrogel network.

[0059] Performance testing of PAA / SBMA / MXene / SA hydrogels

[0060] 1 Mechanical performance test

[0061] like Figure 5 As shown in (a), the compressive stress of the hydrogel first increases and then decreases with increasing MXene concentration. Among them, PABM3 hydrogel exhibits the best compressive performance, with a compressive stress greater than 150 kPa. Figure 5 (b) This is mainly attributed to the abundant surface functional groups on MXene nanosheets, which can provide physical cross-linking points through various non-covalent interactions, significantly improving the mechanical properties of the hydrogel. However, the addition of too much MXene can lead to the aggregation and recombination of MXene nanosheets during the mechanical deformation of the hydrogel, resulting in a decrease in the mechanical properties of the hydrogel. Figure 5 (c) illustrates the compressive behavior of hydrogels with different SA mass fractions. As the SA concentration increases, the maximum compressive stress of the hydrogel also shows a trend of first increasing and then decreasing. Figure 5 (d)). The network structure formed by SA can effectively disperse stress, giving it better ductility and deformability during tension and compression. However, excessively high SA content can lead to an overly dense hydrogel network, restricting molecular chain migration and thus reducing its mechanical properties. Therefore, PABM3S3 hydrogel was chosen as the subject of subsequent research, and is referred to as PABMS for short. Figure 5 (e) and Figure Figure 5 (f) shows that, compared with hydrogels without MXene and SA, PABMS hydrogels exhibit higher compression performance in compression tests, indicating that the introduction of MXene and SA significantly improves the mechanical properties of hydrogels.

[0062] like Figure 6 (a) and Figure 6As shown in (b), when the compressive strain increases from 10% to 90%, the maximum stress and dissipated energy of the PABMS hydrogel both increase significantly, which fully demonstrates that the hydrogel possesses excellent resistance to external strain and compressive resilience. Furthermore, cyclic compression experiments (6(c)) revealed that the stress-strain curves of the hydrogel highly overlapped after 50 compression cycles, with minimal change in the maximum compressive stress (6(d)). This excellent fatigue resistance is mainly attributed to the presence of multiple reversible interaction mechanisms, such as hydrogen bonds, within the hydrogel network.

[0063] 2. Anti-swelling performance test

[0064] When operating in underwater environments, hydrogels, due to their inherent swelling properties, allow water molecules to easily penetrate their interior, causing conductive components to diffuse between interfaces and leading to a decline in electrical properties. Therefore, excellent anti-swelling ability is crucial for maintaining the stable electrical properties of hydrogels in underwater applications. Figure 7 As shown in (a), the PABMS hydrogel exhibits a high water contact angle, demonstrating good hydrophobic properties. The sulfonic acid groups (-SO3) in SBMA... - The electrostatic interaction between the PABMS hydrogel and the MXene surface enhances its anti-swelling properties. Further investigation into the swelling behavior of the hydrogel revealed that, as observed in SEM images (7(b), 7(c)) of the PABMS hydrogel before and after immersion in water, the pores of the hydrogel slightly shrank after immersion, but the overall change was not significant, indicating that the hydrogel can maintain structural stability in an aqueous environment. The swelling rate of the hydrogel after immersion in water is shown in 7(d). The PABMS hydrogel exhibits excellent anti-swelling properties, with an equilibrium swelling rate of approximately 15% after 20 days of immersion in water.

[0065] 3 Adhesion performance test

[0066] In practical sensing applications, the strong adhesion between the object's surface and the hydrogel is a key factor in acquiring accurate and stable signals. PABMS hydrogels possess excellent adhesion properties, such as... Figure 8As shown in (a), PABMS hydrogel adheres tightly and firmly to various substrate surfaces. It achieves good adhesion to materials such as plastics, ceramics, and wood. The interfacial adhesion strength of the hydrogel was further evaluated through an overlap shear test, as shown in 8(b). PABMS hydrogel exhibited varying degrees of adhesion strength to different substrates, with adhesion strengths of 31.34, 35.20, 34.21, 38.04, and 32.87 kPa to plastics, glass, metals, wood, and rubber, respectively. The hydrogel underwent five repeated adhesion tests on different substrate surfaces, and the changes in adhesion strength are shown in 8(c). Although the adhesion strength decreased to some extent after five repeated adhesion tests, PABMS still maintained repeatable adhesion capabilities overall, fully demonstrating its reliability and stability under multiple usage scenarios.

[0067] Example 2

[0068] like Figure 9 As shown, a flexible tactile sensor is assembled by using PABMS hydrogel as the sensing layer and polydimethylsiloxane (PDMS) as the flexible shielding layer.

[0069] Underwater Sensing Research on Anti-Swelling High-Sensitivity Hydrogel Flexible Tactile Sensor

[0070] 1. Sensor performance test

[0071] The introduction of MXene into PABMS hydrogels to construct a continuous conductive network effectively improves the sensing performance of the hydrogels. A detailed study of its underwater sensing performance was conducted.

[0072] As shown in 10(a), the sensitivity of the PABMS hydrogel sensor is much higher than that of PAA and PAB hydrogels. The introduction of MXene as a conductive filler significantly enhances the conductivity of the hydrogel. As shown in 10(b), the PABMS hydrogel sensor exhibits relatively high sensitivity in the pressure range of 0–30 kPa. Figure 10 Figures (c) and (d) demonstrate the signal changes of the hydrogel sensor under different pressure and deformation conditions. The relative resistance change of the sensor increases significantly with increasing pressure or deformation, and its output waveform remains stable throughout multiple load-unload cycles. This phenomenon fully demonstrates that the hydrogel sensor has good stability and repeatability, and can work continuously and reliably in practical applications.

[0073] To further investigate the sensor's performance, the response recovery time of the PABMS hydrogel sensor was tested. For example... Figure 11 As shown in (a), the sensor's response / recovery times are 360ms and 420ms, respectively, demonstrating its fast response characteristics. Figure 11As shown in (b), the sensor exhibits a good linear IV curve under different pressures, indicating that the PABMS hydrogel possesses a perfect conductive network over a wide pressure range. This stable conductive network provides a reliable conductive transmission path for the sensor, thus ensuring the stability of its sensing performance. Furthermore, the mechanical bending performance of the sensor was comprehensively evaluated. The hydrogel sensor was attached to a flexible plastic plate to monitor the response changes at different bending angles (10, 30, 45, and 60°). Figure 11 (c) Experimental results show that the hydrogel sensor exhibits excellent stability under stepped strain. Figure 11 (d)). These results demonstrate that the sensor maintains stable response characteristics under different conditions, confirming the feasibility of its application under high bending and deformation conditions and laying a solid foundation for its practical application in complex environments.

[0074] To further evaluate the sensing performance of the hydrogel sensor under different underwater depth conditions, its response characteristics in different water depth environments were systematically tested. For example... Figure 12 As shown in (a), in the experiment, the sensor was placed at depths of 0cm, 2cm, 4cm, and 6cm above the water surface to monitor the underwater vibration signal generated when an iron ball falls from a height of 40cm above the water surface and 20cm away from the sensor. Figure 12 The results (be) show that the detected response gradually decreases with increasing underwater depth. Simultaneously, the response time slightly increases with depth, possibly related to the absorption and transmission path of mechanical wave energy by the water. However, overall, the differences in response speed and sensitivity between different water depths are not significant, indicating that the hydrogel sensor possesses good depth adaptability and stable underwater sensing performance, meeting the signal detection needs of complex underwater environments.

[0075] 2. Water wave vibration detection

[0076] Water wave vibration detection can provide real-time sensing of the safety status of underwater engineering structures, real-time monitoring of the surrounding environment during exploration, and exploration of marine resources and environmental protection. By monitoring and analyzing vibration signals generated by underwater biological activities, we can understand the distribution and behavioral habits of marine organisms. Fish can sense water wave signals and react sensitively to changes in the surrounding water flow environment, thus cleverly avoiding various potential dangers. Based on this, we conducted in-depth testing of the PABMS hydrogel sensor's ability to sense stimuli from the surrounding water wave environment. Figure 13As shown in (a), the sensor is placed underwater to detect the vibration signal generated by a marble falling onto a table. When the marble is allowed to fall freely from a distance of 10cm from the sensor and from a height of 10cm, 20cm, 30cm, and 40cm above the table, the sensor measures the following signals: Figure 13 As shown in (b), the entire process of the sphere repeatedly colliding with the tabletop can be accurately recorded and distinguished. Figure 13 (c)).

[0077] PABMS hydrogel sensors can sensitively detect signals generated by stomping while running. Figure 14 (a)) clearly distinguishes the vibration signals generated by hammering the ground at different frequencies. Figure 14 (b)). For example Figure 14 As shown in (c), the sensor can quickly detect the ripples when a fishhook falls onto the water surface, and exhibits high sensitivity in sensing minute mechanical vibrations on the liquid surface, such as water bottles or tree branches falling into the water. Figure 14 (d) This fully demonstrates the enormous application potential of PABMS hydrogel sensors in underwater monitoring, underwater communication, and underwater early warning.

[0078] 3. Tactile perception

[0079] To verify the performance of the PABMS hydrogel-based flexible tactile sensor in tactile perception detection, a flexible sensing array was designed to detect pressure distribution. For example... Figure 15 As shown in (ac), objects of different shapes, such as circular weights, rod-shaped weights, and triangular weights, are placed on the surface of the sensor array, and the sensor can generate corresponding response signals. The flexible tactile sensor array of PABMS hydrogel can clearly distinguish objects of different shapes and clearly reflect the corresponding pressure distribution characteristics, which lays a foundation for the practical application of flexible tactile sensors in object recognition, smart homes, and other fields.

[0080] like Figure 16 As shown in (ac), pressure is applied by drawing the letters "U", "P", and "C" with different contact shapes on the surface of the tactile sensor array. The detected sensor signals can provide positional information, thus enabling sensitive touch recognition. When a finger continuously writes the letter "Z" on the sensor array, the corresponding output signal of the sensor is as follows: Figure 17 As shown in (ab), the movement trajectory of the finger can be clearly identified in a time sequence. The flexible tactile sensor based on PABMS hydrogel not only has excellent static shape recognition capabilities, but also exhibits outstanding dynamic trajectory capture characteristics. This perceptual advantage makes it show great application potential in cutting-edge fields such as smart wearable devices and bionic robotic skin, especially in building natural and efficient human-computer interaction interfaces.

[0081] 4. Object Shape Recognition

[0082] The underwater environment is complex and variable, with factors such as insufficient light and turbid water limiting the capabilities of traditional visual and optical sensors. Tactile sensors, by directly contacting the target object, can acquire its feature information in real time, providing underwater robots with another important means of perception. This capability is crucial for underwater robots to perform tasks such as autonomous navigation, obstacle avoidance, target detection, and grasping. Figure 18 As shown in (a), integrating sensors into the mechanical gripper actuator creates a biomimetic underwater sensing end effector, significantly improving the underwater robot's environmental adaptability. Figure 18 As shown in (b), during the grasping action of the robotic gripper, the tactile sensor array can sense the contact force during grasping and identify the shape characteristics of the grasped object. Taking a typical triangular prism grasping experiment as an example, when the robotic gripper performs the grasping action, the multi-channel output signal of the tactile sensor and the pressure mapping are as follows: Figure 18 (e) and Figure 18 As shown in (f), this tactile perception-based object shape recognition technology not only enhances the perception capabilities of underwater robots and builds a safe and reliable grasping control system through a real-time force feedback mechanism, thereby improving the safety and reliability of underwater operations, but also promotes the development of underwater detection and identification technologies, expands the application areas of tactile sensors, and is expected to realize underwater intelligent interaction and operation.

[0083] Example 3

[0084] Visual-touch fusion perception system for robot grasping tasks

[0085] In practical robotic grasping tasks, insufficient grasping stability is a common problem, with grasping slippage being the most frequent, affecting the success rate of grasping tasks. This invention constructs a vision-tactile fusion perception system for grasping tasks based on an anti-swelling conductive hydrogel. By simultaneously acquiring and fusing visual images and tactile signals under different states, it improves the overall stability and intelligence of grasping. The entire system mainly includes a visual recognition and positioning system, a tactile signal acquisition system, a signal processing unit, and a system software interface. The overall system design block diagram is shown below. Figure 19 As shown.

[0086] (1) Target object recognition and localization: The camera acquires environmental information and uses visual algorithms to identify the position, shape, color and material characteristics of the target object, providing position coordinates for the robotic gripper.

[0087] (2) Flexible tactile perception and signal feedback: The hydrogel-based tactile sensor detects the contact state between the robot end effector and the target object in real time, obtains information such as pressure and contact force, collects and processes the signal through hardware circuits, and wirelessly transmits it to the host computer.

[0088] (3) Visual and tactile data fusion and grasping strategy optimization: Visual and tactile information are processed in a coordinated manner, the grasping status is judged based on real-time tactile feedback, the grasping strategy is optimized, and the adaptability and success rate of grasping are improved.

[0089] (4) Real-time display: The camera shooting interface, tactile sensing signals and grasping status judgment results are displayed in real time on the host computer interface so that users can observe and operate.

[0090] Design of tactile signal acquisition system

[0091] The highly sensitive, anti-swelling hydrogel prepared in Example 1, due to its excellent electrosensing properties, can be integrated onto the surface of a mechanical gripper to sense the contact force during grasping. Tactile sensors are fundamental to tactile signal acquisition systems, converting tactile information from robot-object interactions into electrical signals. Because the flexible tactile sensor based on the anti-swelling conductive hydrogel possesses excellent conductivity and long-term stability, it is chosen as the sensing unit for the tactile signal acquisition system.

[0092] The construction of a tactile database is fundamental to the development and training of tactile perception algorithms. It primarily involves storing optimal grasping information for target objects and cooperating with a visual recognition system to detect the grasping state. First, the optimal grasping force signal from the tactile database is pre-acquired. When the robot performs a grasping task, it visually identifies the target object, and the tactile information acquisition system extracts the corresponding grasping force value based on the pre-acquired grasping force data in the database to ensure an appropriate grasping force. The grasping force information varies for different objects, mainly depending on the object's material, mass, and surface morphology. A series of experimental scenarios are designed to collect real-world data. Figure 20 To simulate the diversity of target objects, we selected objects of different shapes, sizes, and materials (such as softness, hardness, smoothness, or roughness); we tried various grasping postures such as parallel grasping and pinching to reflect the uncertainty of grasping methods; at the same time, we applied different forces from slight contact to stable grasping to reflect the range of force variation.

[0093] During the experiment, tactile sensors were used to accurately record tactile data under various conditions, and key information such as object labels and grasping force were recorded simultaneously to ensure the comprehensiveness and practicality of the database. Common objects such as sea cucumbers and starfish were used as examples to conduct tests with different grasping forces to obtain the optimal grasping force values. The test results are as follows: Figure 21 As shown.

[0094] The test objects are selected from examples that take into account different masses, flexibility, structure and surface characteristics. For lighter and softer objects (such as sea cucumbers), a smaller gripping force (1N) should be used to avoid damaging the tissue. For heavier hard shellfish (such as snails and oysters), a higher gripping force (5N) is required to prevent the object from slipping. For medium-mass or irregularly shaped objects (such as scallops and starfish), a moderate gripping force (3N or 4N) is required to ensure a stable grip.

[0095] This embodiment focuses on researching underwater grasping tasks for robots, proposing and implementing a vision-touch fusion intelligent grasping scheme to improve the grasping ability and stability of the robotic gripper in complex environments. The visual perception component acquires and processes images of underwater objects, and optimizes target recognition accuracy through model training, providing visual information support for accurate grasping. By constructing a tactile database, designing signal acquisition hardware circuits and software interfaces, real-time force monitoring during object grasping is achieved, providing real-time tactile perception for the grasping process. Based on this, the system software is developed by integrating visual and tactile perception information, enabling real-time monitoring and grasping status judgment during the grasping process. Comparative experiments verify the superiority of vision-touch fusion technology in robotic gripping. This embodiment demonstrates that the vision-touch fusion perception system can effectively improve the success rate and stability of grasping tasks, overcoming the limitations of single vision or single touch in complex environments, and providing a more reliable perception and control scheme for intelligent grasping tasks. This provides theoretical and experimental basis for future applications in fields such as industrial automation, robotic operation, and underwater operations.

[0096] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an anti-swelling hydrogel strain sensor, characterized in that, Includes the following steps: (1) Add sodium alginate (SA) to the MXene solution and stir until completely dissolved to obtain mixed solution I; the MXene solution is a solution of Ti3C2Tx MXene nanosheets synthesized by selective etching of aluminum elements in Ti3AlC2 using a mixed solution of LiF and HCl; the concentration of the MXene solution is 3wt%; (2) Then add AA, SBMA, crosslinking agent and initiator to mixed solution I; Mixed solution II was obtained by stirring until homogeneous; the mass ratio of SA, MXene solution, AA, and SBMA was 0.3:10:1.72:1.68; mixed solution II was degassed in a vacuum and polymerized in situ at 60°C to obtain an anti-swelling hydrogel; (3) Assemble a strain sensor by using the anti-swelling hydrogel as the sensing layer.

2. The method for preparing an anti-swelling hydrogel strain sensor as described in claim 1, characterized in that, The MXene solution is prepared as follows: Weigh 1.5-2g of LiF and add it to 30mL of HCl solution in a 30-35℃ water bath, stirring for 5-10 minutes. Then, add 2-2.5g of aluminum carbide powder to the above solution while stirring for 5-8 minutes at 30-35℃. Continue stirring for 30-35 hours to ensure the reaction is complete. After the reaction, remove the solution and wash the mixture thoroughly with deionized water, then centrifuge until no supernatant is produced. The pH of the solution is checked to be greater than 6. The resulting solution is ultrasonically treated for 0.5-1 hour, maintaining the temperature below 35℃, and then subjected to a further ultrasonic treatment at 3000-3500 rpm. -1 Centrifuge for 5-8 minutes to obtain MXene solution.

3. The method for preparing an anti-swelling hydrogel strain sensor as described in claim 1 or 2, characterized in that, The crosslinking agent is an MBAA solution, the initiator is an AIBI solution, the concentration of the crosslinking agent is 1 wt%, the concentration of the AIBI solution is 10 wt%, and the mass-volume ratio of the MXene solution to the MBAA solution and the AIBI solution is 10 g : (180-200) μL : (160-180) μL.

4. The anti-swelling hydrogel strain sensor prepared by the preparation method according to any one of claims 1 to 3.

5. The anti-swelling hydrogel strain sensor as described in claim 4, characterized in that, The strain sensor is an underwater flexible tactile strain sensor.

6. The anti-swelling hydrogel strain sensor as described in claim 4, characterized in that, A flexible tactile strain sensor is assembled by using an anti-swelling hydrogel as the sensing layer and polydimethylsiloxane as the flexible shielding layer.

7. A visual-touch fusion sensing system, characterized in that, The system includes a visual recognition and positioning system, a tactile signal acquisition system, a signal processing unit, and a system software interface; the sensing unit of the tactile signal acquisition system is the strain sensor as described in claim 4.

8. The application of the visual-touch fusion sensing system as described in claim 7 in the fields of underwater robots, underwater exploration, and human-computer interaction.

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