Preparation method and application of strain sensor based on tough hydrogel
By integrating MXene nanosheets and tannin acid in conductive hydrogels, a high-strength strain sensor is prepared, which solves the problems of high Young's modulus and poor biocompatibility of wearable conductive hydrogels, and achieves efficient sensing signal output and long-term stability, which is suitable for wearable electronic skin applications.
Patent Information
- Application Number
- CN202510523488.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-07-25
AI Technical Summary
The existing wearable conductive hydrogels have high modulus, poor biocompatibility and poor responsiveness, which limit their application and long-term stability in flexible wearable devices.
The MXene two-dimensional nanosheets were integrated into PEDOT:PSS/PVA dual network hydrogel, supplemented with tannin soaking, and prepared a high-strength and tough conductive hydrogel, and assembled into a sandwich structure strain sensor, using 3M VHB tape as the encapsulation layer.
It achieves high strength, toughness and excellent mechanical properties, ensures stable output of sensor signals, has wide range, high linearity and cyclic stability, and is suitable for real-time monitoring of wearable electronic skin.
Smart Images
Figure CN120368831A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of materials science, and particularly relates to a preparation method and application of a strain sensor based on a tough hydrogel. Background Art
[0002] With the rapid development of information technology, including 5G communication and artificial intelligence, flexible electronic products that were previously confined to the field of science fiction are becoming the focus of the digital market. Compared with traditional rigid wearable monitoring devices, flexible and stretchable wearable electronic devices can adapt to the deformation of human joints, exhibiting various mechanical deformation behaviors including bending, folding, and twisting. Moreover, external physical signal changes can be converted into internal electrical signal changes, and they are widely used in various fields such as electronic skin, motion monitoring, human-machine interfaces, and flexible energy storage devices. However, their inherent brittleness and weak mechanical strength significantly limit their applications and long-term stability. Biological tissues such as muscles and ligaments have amazing high strength, low modulus, high toughness, and long-term robustness. This unparalleled fatigue resistance stems from their highly ordered hierarchical structure. Inspired by this, the present invention integrates MXene two-dimensional nanosheets into a PEDOT:PSS / PVA double-network hydrogel by an evaporation-induced orientation method, assisted by tannic acid soaking enhancement, to prepare a high-strength and tough conductive hydrogel, and assemble it into a strain sensor, which can be attached to different parts of the human body for real-time monitoring of signals. Summary of the Invention
[0003] Aiming at many problems of existing wearable conductive hydrogels such as high Young's modulus, poor biocompatibility, and poor responsiveness, the present invention proposes a preparation method and application of a strain sensor based on a tough hydrogel.
[0004] To achieve the above object, the technical solutions adopted by the present invention are as follows:
[0005] A strain sensor based on a tough hydrogel, the overall structure of the strain sensor is a sandwich structure, the middle conductive hydrogel serves as a sensing layer, and the 3M VHB tape covered on both sides serves as a packaging layer.
[0006] Further, the thickness of the packaging layer is 1.1 mm, and the thickness of the sensing layer is 0.1 - 0.15 mm.
[0007] A preparation method of the above strain sensor based on a tough hydrogel, the method is:
[0008] Step 1: Preparation of MXene dispersion
[0009] The preparation of Ti3C2Tx MXene powder adopts the mixed acid salt etching method: Dissolve 6 g of lithium fluoride into 100 ml of hydrochloric acid solution with a concentration of 9 mol / L to obtain the hydrochloric acid / lithium fluoride etching solution; then slowly add aluminum titanium carbide powder into 100 ml of the etching solution, magnetically stir the mixed solution, control the stirring speed at 1500 r / min, and react for 30 h; centrifuge the reacted solution multiple times, and continuously shake it by hand during the two centrifugations to make the MXene layer, until the pH value of the upper layer solution is 6. Add 40 ml of deionized water to the lower precipitate after centrifugation, vortex it in a vortex oscillator for 30 min, and then centrifuge the vortexed solution multiple times for 30 min, control the rotation speed during the centrifugation process at 1500 r / min, and collect the supernatant to obtain the MXene dispersion;
[0010] Step 2: Preparation of the tough and conductive hydrogel
[0011] When preparing the hydrogel, first add PVA powder into the glycerol aqueous solution (10 wt%) at 100 °C and continuously stir for 1 h to obtain the PVA solution; cool the solution to room temperature, add PEDOT:PSS and 5 mL of 4 mg / mL MXene dispersion, and stir well to ensure uniform mixing of the components. Control the mass concentration of PVA in the mixed solution at 5 wt% and the mass concentration of PEDOT:PSS at 25 wt%; add 50 μL of glutaraldehyde as a chemical cross-linking agent into the mixture, stir the solution well again, inject it into the open mold, and place it for 12 hours to cure and form a PVA film; immerse the obtained composite film in a 10 - 15 wt% tannic acid solution, and after sufficient reaction, obtain the PPMT hydrogel;
[0012] Step 3: Preparation of the strain sensor
[0013] The whole is a sandwich structure. The conductive hydrogel in the middle serves as the sensing layer, and the 3M VHB tape covered on both sides serves as the encapsulation layer. Two copper foil tapes are led out from both ends of the conductive hydrogel and connected to a multimeter to detect the change of the resistance signal during the deformation process.
[0014] Furthermore, in Step 1, 4 - 7 g of aluminum titanium carbide powder is put in.
[0015] Furthermore, in Step 1, the mixed solution is magnetically stirred at 50 - 70 °C.
[0016] Furthermore, in Step 1, the rotation speed during the first centrifugation process is 3500 - 6000 r / min.
[0017] Furthermore, in Step 1, 15 - 20 ml of supernatant is collected each time.
[0018] Further, in Step 2, the PVA / PEDOT:PSS mixed solution doped with MXene is sufficiently stirred for 6 - 8 hours.
[0019] Further, in Step 2, the curing temperature is 25°C - 90°C.
[0020] An application of the above-mentioned strain sensor based on a tough hydrogel, where the conductive hydrogel is clamped to a mechanical tensile machine or applied to a human joint, and two copper foil tapes are led out from both ends of the conductive hydrogel and connected to a multimeter to detect the change in resistance signal during the deformation process.
[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: This hydrogel has an excellent combination of mechanical properties, with a strength of 13.4 ± 1.1 MPa and a toughness as high as 164.6 ± 25.6 MJ / m 3 , and has excellent lubricity. At the same time, its internal uniformly dense conductive network ensures a stable sensing signal output. The approach proposed in the present invention provides a general strategy for designing tough conductive hydrogels and injects new vitality into the multi-field applications of wearable electronic devices. Description of the Drawings
[0022] Figure 1 It is the stress-strain curve diagram of the conductive hydrogel obtained in Step 2 of Example 1.
[0023] Figure 2 It is the sensitivity schematic diagram of the conductive hydrogel strain sensor obtained in Step 3 of Example 1 under 0% - 600% strain.
[0024] Figure 3 It is the diagram of the resistance change (from 0.5% to 5%) of the conductive hydrogel sensor obtained in Step 3 of Example 1 under different strains.
[0025] Figure 4 It is the diagram of the resistance change (from 100% to 600%) of the conductive hydrogel sensor obtained in Step 3 of Example 1 under different strains.
[0026] Figure 5 It is the resistance response diagram of the conductive hydrogel sensor obtained in Step 3 of Example 1 during loading-unloading in a series of steps (each step is 100%) from 0% to 600%.
[0027] Figure 6 It is the schematic diagram of the cyclic stability of the conductive hydrogel sensor obtained in Step 3 of Example 1 within 1000 cycles under 100% strain. Detailed Embodiments
[0028] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.
[0029] The present invention integrates MXene two-dimensional nanosheets into PEDOT:PSS / PVA double network hydrogels by evaporation-induced orientation, and assisted by tannic acid soaking enhancement to prepare a highly strong and tough conductive hydrogel. Its internal uniform and dense conductive network ensures stable sensor signal output, providing a general strategy for designing robust and conductive hydrogels.
[0030] Example 1
[0031] A strain sensor based on a tough hydrogel and a preparation method and application thereof, comprising the following steps:
[0032] Step 1: Preparation of MXene dispersion
[0033] Ti3C2T x The preparation of MXene powder adopts the mixed salt etching method. Lithium fluoride is dissolved in 100ml of hydrochloric acid solution with a concentration of 9mol / L to obtain hydrochloric acid / lithium fluoride etching solution. Then 4g of titanium carbide aluminum powder is slowly added to 100ml etching solution. The mixed solution is magnetically stirred at 50℃, and the stirring speed is controlled to 1500r / min. The reaction is 30h. The solution after the reaction is centrifuged several times at a speed of 3500r / min. During this period, the MXene is continuously shaken by hand to stratify until the pH value of the upper liquid is 6. 40ml of deionized water is added to the lower sediment after centrifugation, and vortexed in a vortex oscillator for 30min. The vortexed solution is centrifuged for 30min multiple times, and 15ml of supernatant is collected to obtain MXene dispersion. The speed of the centrifugal process is controlled to be 1500r / min.
[0034] Step 2: Preparation of strong conductive hydrogel
[0035] When preparing the hydrogel, PVA powder was first added to a glycerol aqueous solution (10wt%) at 100°C and stirred for 1 hour to obtain a 5wt% PVA solution. The solution was then cooled to room temperature, and then PEDOT:PSS (25wt%) and MXene dispersion were added and stirred for 6h to ensure uniform mixing of the components. Glutaraldehyde was then added to the mixture as a chemical cross-linking agent, and the solution was stirred again, injected into an open mold, and placed at 30°C for 12 hours to solidify to form a PVA film. Finally, the obtained composite film was immersed in a 10wt% tannic acid solution, and after sufficient reaction, the PPMT hydrogel was obtained.
[0036] Step 3: Preparation of strain sensor
[0037] The overall structure is a sandwich structure. The middle conductive hydrogel serves as the sensing layer, and the 3M VHB tapes covered on both sides serve as the encapsulation layer. Two copper foil tapes are led out from both ends of the conductive hydrogel and connected to a multimeter to detect the change in resistance signal during the deformation process. The tough conductive hydrogel prepared in this example has a strength of 13.4 ± 1.1 MPa, an elongation at break of 2337 ± 246.2%, and a toughness of 164.6 ± 25.6 MJ / m 3 . In addition, as a strain sensor, it also has a wide measurement range, high linearity, good sensitivity and cyclic stability. As Figure 2 shown, the linearity R 2 is about 0.99, and the sensitivity can reach 0.66 under 200 - 600% strain. In order to demonstrate the excellent performance of this strain sensor, the present invention shows its application as a wearable electronic skin, which can continuously monitor human motion signals and subtle physiological signals.
[0038] Example 2
[0039] A strain sensor based on a tough hydrogel, its preparation method and application, comprising the following steps:
[0040] Step 1: Preparation of MXene dispersion
[0041] Ti3C2T x The MXene powder is prepared by the mixed acid salt etching method. Lithium fluoride is dissolved in 100 ml of hydrochloric acid solution with a concentration of 9 mol / L to obtain a hydrochloric acid / lithium fluoride etching solution. Then, 5 g of aluminum titanium carbide powder is slowly added to 100 ml of the etching solution. The mixture is magnetically stirred at 60 °C, and the stirring speed is controlled at 1500 r / min for 30 h. The reaction solution is centrifuged at a speed of 5000 r / min for multiple times. During this period, continuously shake by hand to make the MXene layer, until the pH value of the upper layer solution is 6. 40 ml of deionized water is added to the centrifuged lower precipitate, and it is vortexed in a vortex oscillator for 30 min. Then, the vortexed solution is centrifuged for 30 min for multiple times, and 15 ml of the supernatant is collected to obtain the MXene dispersion, and the rotation speed during the centrifugation process is controlled at 1500 r / min.
[0042] Step 2: Preparation of tough conductive hydrogel
[0043] When preparing the hydrogel, first add PVA powder to the glycerol aqueous solution (10 wt%) at 100 °C and continuously stir for 1 hour to obtain a 5 wt% PVA solution. Then cool the solution to room temperature, and then add PEDOT:PSS (25 wt%) and the MXene dispersion, and stir well for 7 h to ensure uniform mixing of the components. Then add glutaraldehyde as a chemical cross-linking agent to the mixture, stir the solution well again, inject it into an open mold, and place it at 50 °C for 12 hours to cure and form a PVA film. Finally, immerse the obtained composite film in a 15 wt% tannic acid solution, and after sufficient reaction, obtain the PPMT hydrogel.
[0044] Step 3: Preparation of the strain sensor
[0045] The overall structure is a sandwich structure. The conductive hydrogel in the middle serves as the sensing layer, and the 3M VHB tape covered on both sides serves as the encapsulation layer. Two copper foil tapes are led out from both ends of the conductive hydrogel and connected to a multimeter to detect the change in the resistance signal during the deformation process.
[0046] Example 3
[0047] A strain sensor based on a tough hydrogel, its preparation method and application, including the following steps:
[0048] Step 1: Preparation of the MXene dispersion
[0049] Ti3C2T x The MXene powder is prepared by the mixed acid salt etching method. Dissolve lithium fluoride in 100 ml of hydrochloric acid solution with a concentration of 9 mol / L to obtain the hydrochloric acid / lithium fluoride etching solution. Then slowly add 7 g of titanium aluminum carbide powder to 100 ml of the etching solution, magnetically stir the mixture at 70 °C, control the stirring speed at 1500 r / min, and react for 30 h. Centrifuge the reacted solution at a speed of 6000 r / min multiple times. During this period, continuously shake by hand to stratify the MXene until the pH value of the upper layer solution is 6. Add 40 ml of deionized water to the centrifuged lower precipitate, vortex in a vortex oscillator for 30 min, and then centrifuge the vortexed solution multiple times for 30 min. Collect 20 ml of the supernatant to obtain the MXene dispersion, and control the rotation speed during the centrifugation process at 1500 r / min.
[0050] Step 2: Preparation of the tough conductive hydrogel
[0051] When preparing the hydrogel, first add PVA powder into the glycerol aqueous solution (10 wt%) at 100 °C and continuously stir for 1 hour to obtain a 5 wt% PVA solution. Then cool the solution to room temperature, and then add PEDOT:PSS (25 wt%) and MXene dispersion, and stir well for 8 h to ensure uniform mixing of the components. Then add glutaraldehyde as a chemical crosslinking agent into the mixture, stir the solution well again, inject it into an open mold, and place it at 90 °C for 12 hours to cure and form a PVA film. Finally, immerse the obtained composite film into a 15 wt% tannic acid solution, and after sufficient reaction, obtain the PPMT hydrogel.
[0052] Step 3: Preparation of the strain sensor
[0053] The overall structure is a sandwich structure. The conductive hydrogel in the middle serves as the sensing layer, and the 3M VHB tape covered on both sides serves as the encapsulation layer. Two copper foil tapes are led out from both ends of the conductive hydrogel and connected to a multimeter to detect the change in the resistance signal during the deformation process.
Claims
1. A strain sensor based on a tough hydrogel, characterized in that: The overall strain sensor has a sandwich structure, with the middle conductive hydrogel as the sensing layer and the tape covered on both sides as the encapsulation layer.
2. The strain sensor based on the tough hydrogel according to claim 1, characterized in that: The encapsulation layer is 1.1 mm, and the sensing layer is 0.1 - 0.15 mm.
3. A method for preparing a strain sensor based on a tough hydrogel according to claim 1 or 2, characterized in that: The method is as follows: Step 1: Preparation of MXene dispersion The preparation of Ti3C2Tx MXene powder uses the mixed acid salt etching method: Dissolve 6 g of lithium fluoride in 100 ml of hydrochloric acid solution with a concentration of 9 mol / L to obtain the hydrochloric acid / lithium fluoride etching solution; then slowly add aluminum titanium carbide powder to 100 ml of the etching solution, magnetically stir the mixed solution, control the stirring speed at 1500 r / min, and react for 30 h; Centrifuge the reaction solution multiple times, and continuously shake the solution by hand during the two centrifugations to make the MXene layer, until the pH value of the upper layer solution is 6. Add 40 ml of deionized water to the centrifuged lower precipitate, vortex for 30 min in a vortex oscillator, and then centrifuge the vortexed solution multiple times for 30 min, control the rotation speed during the centrifugation process at 1500 r / min, and collect the supernatant to obtain the MXene dispersion; Step 2: Preparation of tough and conductive hydrogel When preparing the hydrogel, first add PVA powder to the glycerol aqueous solution (10 wt%) at 100 °C and continuously stir for 1 h to obtain the PVA solution; Cool the solution to room temperature, add PEDOT:PSS and 5 mL of 4 mg / mL MXene dispersion, and stir well to ensure uniform mixing of the components. Control the mass concentration of PVA in the mixed solution at 5 wt% and the mass concentration of PEDOT:PSS at 25 wt%; Add 50 μL of glutaraldehyde as a chemical crosslinking agent to the mixture, stir the solution well again, inject it into the open mold, and place it for 12 hours to cure and form a PVA film; Immerse the obtained composite film in a 10 - 15 wt% tannic acid solution, and after sufficient reaction, obtain the PPMT hydrogel; Step 3: Preparation of strain sensor The overall structure is a sandwich structure, with the middle conductive hydrogel as the sensing layer and the 3M VHB tape covered on both sides as the encapsulation layer. Two copper foil tapes are led out from both ends of the conductive hydrogel and connected to a multimeter to detect the change in resistance signal during the deformation process.
4. The preparation method according to claim 3, characterized in that: In Step 1, 4 - 7 g of aluminum titanium carbide powder is put in.
5. The preparation method according to claim 3, characterized in that: In Step 1, the mixed solution is magnetically stirred at 50 - 70 °C.
6. The preparation method according to claim 3, characterized in that: In Step 1, the rotation speed during the first centrifugation process is 3500 - 6000 r / min.
7. The preparation method according to claim 3, characterized in that: In Step 1, 15 - 20 ml of supernatant is collected each time.
8. The preparation method according to claim 3, characterized in that: In Step 2, the doped MXene PVA / PEDOT:PSS mixed solution is stirred well for 6 - 8 hours.
9. The preparation method according to claim 3, characterized in that: In Step 2, the curing temperature is 25 °C - 90 °C.
10. Use of the strain sensor based on tough hydrogel according to claim 1 or 2, characterized in that: Clamp the conductive hydrogel to a mechanical tensile machine or apply it to a human joint. Two copper foil tapes are led out from both ends of the conductive hydrogel and connected to a multimeter to detect the change in resistance signal during the deformation process.