Biomimetic movement and sensing dual-functional fish tendon based on hydrogel material

Abstract

This invention provides a hydrogel-based biomimetic dual-function fish tendon for both movement and sensing, comprising the following steps: adding a PEDOT:PSS solution to a PVA solution and stirring until homogeneous to obtain a PVA-PEDOT:PSS mixed solution; then adding a sodium citrate solution to the PVA-PEDOT:PSS mixed solution, stirring thoroughly and precipitating a flocculent precipitate; next, placing the flocculent precipitate in a mold, reacting at room temperature, then freezing at low temperature, and subsequently thawing at room temperature, repeating this freeze-thaw cycle multiple times to obtain the hydrogel-based biomimetic dual-function fish tendon for both movement and sensing. This fish tendon integrates sensing functions into the hydrogel, possessing both movement and sensing functions, enabling the underwater biomimetic robotic fish to perceive its own state in real time during movement and intelligently adjust according to environmental changes, significantly improving the robotic fish's flexibility and autonomy, enhancing its adaptability in complex underwater environments, and making it suitable for manufacturing tendons for underwater robotic fish.

Description

Technical Field

[0001] This invention relates to a biomimetic dual-function fish tendon based on hydrogel material, which combines movement and sensing, and belongs to the field of biomimetic materials technology. Background Technology

[0002] Bionics is a technology inspired by biology, designed to mimic the structure, function, and behavior of biological systems. Through biomimicry, humans can draw inspiration from biological systems to create new materials, devices, and systems to solve real-world problems. Bionics has broad application prospects in fields such as novel materials, sensors, biomedical engineering, robotics, and environmental monitoring.

[0003] Over approximately 500 million years of evolution, fish have continuously developed increasingly sophisticated biological characteristics adapted to aquatic life. For example, tuna possess body curves and proportions suitable for prolonged, high-speed underwater swimming, while catfish have pectoral fins that provide proprioception. These evolutionary advancements have endowed fish with exceptional underwater movement and sensory abilities, becoming a significant source of inspiration for biomimetic research. Based on the biological characteristics of fish, an underwater biomimetic robotic fish has been developed. This robotic fish is primarily used in underwater exploration operations, environmental monitoring, and military reconnaissance, demonstrating multiple advantages such as high propulsion efficiency, strong maneuverability, excellent stealth, and outstanding environmental friendliness.

[0004] However, existing underwater biomimetic robotic fish still face technological limitations. For example, fish tendons are dense fibrous connective tissues that connect muscles to bones, attaching muscles to the skeleton to achieve normal movement. Traditional underwater biomimetic robotic fish often use rigid materials for their tendons, which, while providing some support and mobility, cannot achieve effective sensing functions. This limitation results in the robotic fish lacking real-time awareness of its own state during movement, making it difficult to make timely adjustments based on environmental changes. Furthermore, current technology lacks biomimetic fish tendons that simultaneously possess both movement and sensing functions, leading to reduced overall system coordination and flexibility, and hindering efficient operation in complex environments. Summary of the Invention

[0005] This invention provides a biomimetic dual-function fish tendon based on hydrogel material, which can effectively solve the above-mentioned problems.

[0006] This invention is implemented as follows:

[0007] A method for preparing a biomimetic dual-function fish tendon based on hydrogel for both movement and sensing includes the following steps:

[0008] S1. Add PEDOT:PSS solution to PVA solution and stir until homogeneous to obtain PVA-PEDOT:PSS mixed solution;

[0009] S2, then add sodium citrate solution to PVA-PEDOT:PSS mixed solution, stir thoroughly and precipitate flocculent precipitate;

[0010] S3. Next, the flocculent precipitate is placed in a mold, reacted at room temperature, then frozen at low temperature, and then taken out and thawed at room temperature. This freeze-thaw cycle is repeated many times to obtain the biomimetic movement and sensing dual-function fish tendon based on hydrogel.

[0011] In some embodiments, in step S1, the mass fraction of the PVA is 5-20 wt%.

[0012] In some embodiments, in step S1, the mass fraction of the PEDOT:PSS solution is 1.0-1.3 wt%.

[0013] In some embodiments, in step S2, the concentration of the sodium citrate solution is 1-3 mol / L.

[0014] In some embodiments, in step S1, the volume ratio of the PEDOT:PSS solution to the PVA solution is 1:3 to 1:10.

[0015] In some embodiments, in step S2, the volume ratio of the sodium citrate solution to the PVA solution is 1:10 to 5:10.

[0016] In some embodiments, in step S3, the freezing temperature is -30°C to -20°C, the freezing time is 8-12 hours, and the thawing time is 3-4 hours.

[0017] In some embodiments, in step S3, the number of freeze-thaw cycles is 2-5.

[0018] A biomimetic dual-function fish tendon based on hydrogel, prepared by the above method, for both movement and sensing.

[0019] The application of the above-mentioned hydrogel-based biomimetic dual-function fish tendon for motion and sensing in the preparation of robotic fish.

[0020] The beneficial effects of this invention are:

[0021] This invention achieves an optimized balance between the electrical and mechanical properties of a hydrogel by carefully adding poly(3,4-ethylenedioxythiophene):polybenzenesulfonic acid (PEDOT:PSS), a high-performance conductive material, to a polyvinyl alcohol (PVA) solution, combined with the synergistic effect of sodium citrate solution. This innovative design allows the hydrogel to maintain its excellent stability and conductivity even under complex mechanical conditions such as stretching and deformation. During the movement of the robotic fish, this special hydrogel can sense and accurately capture its own posture and state changes in real time, thereby generating corresponding and diverse electrical signals. These electrical signals serve as important feedback information and are received by the robotic fish's internal control system, enabling it to autonomously adjust and optimize its movement patterns based on these real-time signals to adapt to different underwater environments. This unique self-sensing function is inspired by the muscle sensory system in living organisms. By mimicking the sensory mechanisms of organisms, it endows the robotic fish with greater flexibility and autonomy in complex and ever-changing underwater environments, significantly improving its movement efficiency and adaptability. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a flowchart illustrating the preparation process of the hydrogel-based biomimetic motion and sensing dual-function fish tendon in Example 1.

[0024] Figure 2 The stress-strain curves are shown for the biomimetic motion and sensing dual-function fish tendon based on hydrogel material prepared in Example 1 and the hydrogels prepared in Comparative Examples 1-2.

[0025] Figure 3 The electrical conductivity characterization diagrams are for the biomimetic motion and sensing dual-function fish tendon based on hydrogel material prepared in Example 1 and the hydrogels prepared in Comparative Examples 1-2.

[0026] Figure 4 The graph shows the relative resistance change of the biomimetic motion and sensing dual-function fish tendon of Example 1 of the present invention, which was used as a proprioceptor on a robotic fish. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. 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. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. 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.

[0028] This invention provides a method for preparing a biomimetic dual-function fish tendon based on hydrogel, which includes the following detailed steps:

[0029] S1. First, add PEDOT:PSS solution to the PVA solution and stir thoroughly to ensure uniform mixing, thereby obtaining a PVA-PEDOT:PSS mixed solution. Specifically, the PVA solution preparation process involves adding PVA (polyvinyl alcohol) monomer to deionized water, followed by stirring under water bath heating conditions until the PVA is completely dissolved in pure water, forming a homogeneous PVA solution.

[0030] S2, Next, the pre-prepared sodium citrate solution is added to the above-mentioned PVA-PEDOT:PSS mixed solution and stirred thoroughly to ensure homogeneity. During this process, flocculent precipitates will form. The sodium citrate solution is prepared by adding sodium citrate powder to deionized water and stirring until it is completely dissolved to form a homogeneous sodium citrate solution.

[0031] S3. Then, the flocculent precipitate that has precipitated after stirring is placed in a pre-prepared mold and reacted at room temperature. Subsequently, it is placed in a low-temperature environment for freezing. After freezing, it is removed and thawed at room temperature. This freeze-thaw cycle is repeated multiple times to finally obtain the biomimetic dual-function fish tendon based on hydrogel for both movement and sensing.

[0032] This invention cleverly balances the electrical and mechanical properties of a hydrogel by adding PEDOT:PSS, a conductive material, and sodium citrate solution to a PVA solution, enabling it to maintain stable performance even under stretching and deformation. This special hydrogel material can sense its own posture and state in real time during movement and generate different electrical signals. These signals can be received by the robotic fish, which can then autonomously adjust its movement pattern accordingly, achieving more flexible and autonomous motion control. This self-sensing function is inspired by the muscle sensory system in living organisms. By mimicking this system, the robotic fish can exhibit greater flexibility and autonomy in complex and changing underwater environments, significantly improving its performance and reliability in practical applications.

[0033] In some specific embodiments, during step S1, the mass fraction of the PVA (polyvinyl alcohol) solution used is strictly controlled between 5 wt% and 20 wt% to ensure its stability and effectiveness in subsequent reactions.

[0034] In some specific embodiments, during step S1, the mass fraction of the PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(benzenesulfonic acid)) solution used is also precisely set within the range of 1.0 wt% to 1.3 wt% to optimize its conductivity and solution homogeneity.

[0035] In some detailed embodiments, during step S2, the concentration of the sodium citrate solution used is precisely adjusted between 1 mol / L and 3 mol / L to ensure that it can effectively buffer and stabilize the reaction.

[0036] In some specific embodiments, during the operation of step S1, the volume ratio of the PEDOT:PSS solution to the PVA solution is carefully controlled within the range of 1:3 to 1:10 to achieve the best mixing effect and performance of the two solutions.

[0037] In some specific embodiments, during step S2, the volume ratio of the sodium citrate solution to the PVA solution is also carefully set within the range of 1:10 to 5:10 to ensure that the two solutions can achieve the expected reaction effect and stability after mixing, thereby improving the reliability of the overall process and the quality of the product.

[0038] In some specific embodiments, during step S3, the set freezing temperature range is strictly controlled between -30°C and -20°C to ensure the stability and consistency of experimental conditions. Simultaneously, the freezing time is explicitly specified as 8 to 12 hours, a timeframe chosen to ensure the samples are fully frozen to achieve the desired experimental results. Furthermore, in the thawing stage, the set thawing time is precisely controlled between 3 and 4 hours, an arrangement designed to ensure the samples thaw uniformly and thoroughly, thus laying the foundation for the smooth progress of subsequent experimental steps.

[0039] In some specific embodiments, the number of freeze-thaw cycles performed in step S3 is explicitly limited to between 2 and 5. This number of cycles is based on the results of multiple experimental verifications, aiming to achieve the desired sample processing effect through an appropriate number of freeze-thaw cycles, while avoiding unnecessary damage or impact on the sample due to excessive cycles, thereby ensuring the accuracy and reliability of the experimental results.

[0040] This invention provides a biomimetic dual-function fish tendon based on hydrogel, prepared using the method described above. This fish tendon cleverly integrates sensing functions into the hydrogel material, enabling the underwater biomimetic robotic fish to perceive its own state in real time during movement and intelligently adjust according to changes in the surrounding environment. This innovative design has significant practical implications and application value. This dual-function tendon not only significantly improves the robotic fish's flexibility and autonomy, allowing it to swim more freely in the underwater environment, but also greatly enhances its adaptability to complex and changing underwater environments, ensuring efficient operation under various complex conditions.

[0041] This invention further provides a specific application of a biomimetic dual-function fish tendon based on hydrogel materials in the fabrication of a robotic fish. By applying this dual-function tendon to the manufacture of the robotic fish, not only are the robotic fish's motion performance and sensing capabilities improved, but a solid technical guarantee is also provided for its stable operation in complex underwater environments. This innovative application not only broadens the application fields of hydrogel materials but also opens up new paths for the development of underwater biomimetic robots.

[0042] Example 1: Preparation of a biomimetic dual-function fish tendon based on hydrogel for both motion and sensing.

[0043] (1) Weigh 6g of PVA (polyvinyl alcohol, type 1799) and add it to 54ml of deionized water. Heat and stir in a water bath at 95℃ for 3-4 hours until the PVA is completely dissolved in pure water to prepare a PVA solution with a mass fraction of 10wt%.

[0044] (2) Cool the PVA solution obtained in step (1) to room temperature, and then add 12 ml of commercially available PEDOT:PSS (poly(3,4-ethylenedioxythiophene): polystyrene sulfonic acid) solution to the PVA solution. Stir and mix thoroughly for 0.5 h to form a uniform PVA-PEDOT:PSS mixed solution.

[0045] Adding PEDOT:PSS solution can improve the conductivity of the solution. The mass fraction of PEDOT:PSS solution is 1.0 wt%, the type is PH1000, purchased from Heraeus, and its volume ratio with PVA solution is 1:5.

[0046] (3) Weigh 9.3g of sodium citrate powder and add it to deionized water. Stir for 0.5h until completely dissolved to form 18ml of sodium citrate solution;

[0047] The sodium citrate solution has a concentration of 2 mol / L, and its volume ratio with the PVA solution is 3:10.

[0048] (4) Pour the sodium citrate solution obtained in step (3) into the PVA-PEDOT:PSS mixed solution, stir and mix immediately to precipitate a certain amount of flocculent precipitate and obtain a clear solution;

[0049] (5) Place the above flocculent precipitate in a mold and react at room temperature for 12 hours. Then freeze it at -25°C for 8 hours and take it out. Thaw it at room temperature for 3.5 hours and repeat the freeze-thaw process twice to obtain a biomimetic movement and sensing dual-function fish tendon based on hydrogel material.

[0050] Preparation process as follows Figure 1 As shown.

[0051] Comparative Example 1: Preparation of PVA-Sodium Citrate Hydrogel

[0052] The PVA solution in step (1) of Example 1 was mixed with the sodium citrate solution in step (3). After stirring and mixing, a certain amount of flocculent precipitate was precipitated. The flocculent precipitate was placed in a mold and reacted at room temperature for 12 hours. Then it was frozen at -25°C for more than 8 hours and then taken out. It was thawed at room temperature for 3.5 hours. The freeze-thaw process was repeated twice to obtain PVA-sodium citrate hydrogel.

[0053] Comparative Example 2: Preparation of PVA-PEDOT:PSS hydrogel

[0054] The PVA-PEDOT:PSS mixed solution from step (2) of Example 1 was stirred and mixed to precipitate a certain amount of flocculent precipitate. The flocculent precipitate was placed in a mold and reacted at room temperature for 12 hours. Then it was frozen at -25°C for 8 hours and taken out. It was then thawed at room temperature for 3.5 hours. The freeze-thaw process was repeated twice to obtain PVA-PEDOT:PSS hydrogel.

[0055] Test Example 1: Stress-Strain Relationship Test

[0056] The hydrogels prepared in Example 1 and Comparative Examples 1-2 were used as test samples in this test experiment. The samples were clamped on a tensile testing instrument using a fixture. Before applying the load, the initial length (L0) and cross-sectional area (A0) of the samples were recorded. Then, a tensile force (F) was gradually applied at a constant rate of 20 mm / min, and the corresponding change in sample length (ΔL) was recorded. The tensile instrument continuously recorded the stress (σ = F / A0) and strain (ε = ΔL / L0). The tensile force was continuously applied until the sample fractured, and the maximum stress and the corresponding strain value were recorded. Finally, a curve was plotted based on the recorded stress and strain data. With strain (ε) as the x-axis and stress (σ) as the y-axis, Young's modulus (E = σ / ε) was calculated within the initial stage of the linear interval of the stress-strain relationship curve (the strain range was taken as 5-15% in this experiment).

[0057] The tensile testing instrument used in the experiment was an E43.104 microcomputer-controlled electronic universal testing machine, which was calibrated before testing to ensure normal operation and accurate measurement results. The fixtures underwent adaptability testing before use to ensure they could fix the sample, apply uniform force to both ends, and prevent lateral slippage. The testing environment required suitable temperature and humidity to avoid changes in the properties of the hydrogel material. To improve the reliability of the test results, at least three tests were conducted, and the average value and standard deviation were calculated. The test results are as follows: Figure 2 As shown.

[0058] Figure 2 The stress-strain curves of the biomimetic motion and sensing dual-function fish tendon based on hydrogel material prepared in Example 1, and the hydrogels prepared in Comparative Examples 1-2 are shown. As can be seen from the curves, within the elastic limit of the test samples, the stress and strain exhibit an approximately linear relationship; that is, as the strain increases, the stress increases almost proportionally.

[0059] Young's modulus was calculated in the initial stage of the linear range of the stress-strain curve (range of 5-15% of strain). The results showed that the bionic tendon prepared in Example 1 had a maximum strain exceeding 300% and a Young's modulus of 2.051 MPa; the PVA-sodium citrate hydrogel of Control Example 1 had a maximum strain exceeding 250% and a Young's modulus of 3.409 MPa. The PVA-PEDOT:PSS composite hydrogel of Control Example 2, due to its significantly insufficient toughness and modulus, was difficult to firmly clamp onto the stretching device, and its performance did not significantly improve after multiple freeze-thaw cycles; therefore, stress-strain testing was not performed on it.

[0060] The results show that the bionic tendon prepared in Example 1 exhibits excellent toughness and modulus, and can withstand large loads without breaking, thus meeting the mechanical performance requirements for use as a tendon.

[0061] Test Example 2: Conductivity Characterization Test

[0062] Electrical conductivity, usually represented by the symbol σ, is a physical quantity that describes the ability of a material to conduct electricity, that is, the ability of a material to carry current per unit volume and unit length. It is defined as: σ = L / (R*S), where L represents the original length, R represents the resistance of the material, and S represents the cross-sectional area of ​​the material. Generally, the higher the conductivity, the better the electrical conductivity of the material.

[0063] The test experiment used the biomimetic motion and sensing dual-function fish tendon based on hydrogel material prepared in Example 1 and the hydrogel prepared in Comparative Examples 1-2 as test samples. The original length (L) and cross-sectional area (S) of the samples were measured respectively. Then, the resistance (R) of the samples was measured by directly contacting the hydrogel with electrodes using a resistance measuring instrument and the two-point probe method. Finally, the conductivity was calculated.

[0064] The resistance measuring instrument used in the test experiments was a VC4092C LCR benchtop digital bridge, which was calibrated before measurement to ensure normal operation and accurate results. Vernier calipers were used to measure the sample length and cross-sectional area. Suitable ambient temperature and humidity were required to avoid changes in the properties of the hydrogel material. To improve the reliability of the test results, at least three tests were conducted, and the average value and standard deviation were calculated. The test results are as follows: Figure 3 As shown.

[0065] Figure 3 The biomimetic dual-function fish tendon based on hydrogel material prepared in Example 1, and the conductivity characterization diagrams of the hydrogels prepared in Comparative Examples 1 and 2 are shown. The conductivity of the PVA-PEDOT:PSS-sodium citrate hydrogel prepared in Example 1 was calculated to be 0.883 S / m, the conductivity of the PVA-sodium citrate hydrogel prepared in Comparative Example 1 was 0.017 S / m, and the conductivity of the PVA-PEDOT:PSS hydrogel prepared in Comparative Example 2 was 0.101 S / m.

[0066] The results showed that the conductivity of the biomimetic dual-function fish tendon based on hydrogel material prepared in Example 1 was significantly higher than that of the PVA-sodium citrate hydrogel prepared in Comparative Example 1 and the PVA-PEDOT:PSS hydrogel prepared in Comparative Example 2, by 51.9 times and 8.7 times, respectively. The biomimetic dual-function fish tendon based on hydrogel material prepared in Example 1 of this invention exhibited the best electrical conductivity, far exceeding that of Comparative Examples 1 and 2. This indicates that PVA, PEDOT:PSS, and sodium citrate played a synergistic role, jointly improving the conductivity of the hydrogel.

[0067] Test Example 3: Application Effect Test of Bionic Motion and Sensing Dual-Functional Tendon

[0068] The test experiment used the biomimetic motion and sensing dual-function fish tendon based on hydrogel material prepared in Example 1 as the test sample. Multiple turns of wire were wrapped around both ends of the sample and fixed with insulating black tape to ensure good electrical contact. A robotic fish test model was designed and fabricated, with rectangular channels on both sides of the robotic fish, the size of which was slightly larger than the sample size. The tendon sample was loaded into the pre-set channels of the robotic fish, and the electrode clips connected to the resistance measuring instrument were clamped at different positions on one side of the tendon. At the same time, a pre-tuned program was run, so that the biomimetic motion and sensing dual-function fish tendon based on hydrogel material could drive the tail of the robotic fish to swing, with a swing amplitude of 0-±60°, realizing different left and right turning motion postures. The biomimetic motion and sensing dual-function fish tendon based on hydrogel material has a certain pre-stress when the tail of the robotic fish is straight. The resistance at this time is used as the initial resistance (R0), and the relative resistance change during left and right turning posture swing is recorded (ΔR / R0=(R-R0) / R0).

[0069] The resistance measuring instrument used in the test experiments was a VC4092C LCR benchtop digital bridge, which was calibrated before measurement to ensure normal operation and accurate results. The test required suitable ambient temperature and humidity to avoid changes in the properties of the hydrogel material. To improve the reliability of the test results, at least three tests were performed, and the average value and standard deviation were calculated. The test results are as follows: Figure 4 As shown.

[0070] Figure 4The diagram illustrates the electrical signal characteristics of the biomimetic dual-function fish tendon based on hydrogel material, prepared in Example 1, after being applied as a proprioceptor to a robotic fish (the electrical signal of one tendon was measured). Observations show that in a straight-line state, the tail's left and right swing amplitudes are basically consistent, and the waveform exhibits periodic fluctuations near 0. When the robotic fish turns right, the tail bends more to the right, leading to a decrease in strain of the biomimetic dual-function fish tendon based on hydrogel material, resulting in an overall decrease in relative resistance. Conversely, in a left-turn state, the tail bends more to the left, increasing the tendon's strain and causing an overall increase in relative resistance. By observing the changes in the waveform's vertical movement, the robotic fish's swimming posture can be reflected in real time, allowing for immediate adjustments and thus achieving proprioceptive sensing.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a biomimetic dual-function fish tendon based on hydrogel for both movement and sensing, characterized in that, Includes the following steps: S1. Add PEDOT:PSS solution to PVA solution and stir until homogeneous to obtain PVA-PEDOT:PSS mixed solution; S2, then add sodium citrate solution to PVA-PEDOT:PSS mixed solution, stir thoroughly and precipitate flocculent precipitate; S3, then the flocculent precipitate is placed in a mold, reacted at room temperature, then frozen at low temperature, and then taken out and thawed at room temperature. This freeze-thaw cycle is repeated many times to obtain the biomimetic movement and sensing dual-function fish tendon based on hydrogel. In step S1, the mass fraction of the PVA is 5-20 wt%. In step S1, the mass fraction of the PEDOT:PSS solution is 1.0-1.3 wt%. In step S1, the volume ratio of the PEDOT:PSS solution to the PVA solution is 1:3 to 1:

10. In step S2, the concentration of the sodium citrate solution is 1-3 mol / L; In step S2, the volume ratio of the sodium citrate solution to the PVA solution is 1:10 to 5:

10.

2. The preparation method according to claim 1, characterized in that, In step S3, the freezing temperature is -30℃ to -20℃, the freezing time is 8-12 hours, and the thawing time is 3-4 hours.

3. The preparation method according to claim 1, characterized in that, In step S3, the freeze-thaw cycle is repeated 2-5 times.

4. A biomimetic, motion-sensing, dual-function fish tendon based on hydrogel, prepared according to any one of claims 1 to 3.

5. The application of the hydrogel-based biomimetic motion and sensing dual-function fish tendon as described in claim 4 in the preparation of robotic fish.

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