High-sensitivity flexible sensing composite material and preparation method thereof
By combining a PVA-CMC hydrogel matrix with a silver particle conductive layer, the problem of insufficient mechanical strength and conductivity of flexible strain sensing materials is solved, achieving high-sensitivity strain monitoring, which is suitable for applications such as smart wearable devices and electronic skin.
Patent Information
- Application Number
- CN202411527203.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-30
- Publication Date
- 2025-02-25
AI Technical Summary
Existing flexible strain sensing materials often suffer from compromised mechanical strength while maintaining high sensitivity, and the poor compatibility between conductive fillers and flexible substrates leads to a decline in sensing performance, limiting long-term stability and fatigue resistance.
Using PVA and CMC as matrix materials, a PVA-CMC hydrogel matrix was prepared by low-temperature 3D printing technology. A dense silver particle conductive layer was formed on the surface of the hydrogel by solution immersion reduction method. The conductive functionalization was achieved by combining ascorbic acid and polyvinylpyrrolidone reducing agent solution.
The prepared flexible sensing composite material has high mechanical strength, high conductivity and high sensitivity, and can accurately monitor a variety of strain signals, making it suitable for fields such as smart wearable devices and electronic skin.
Smart Images
Figure CN119505456A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of functional composite material preparation, and in particular to a high-sensitivity flexible sensing composite material and a preparation method thereof. Background Art
[0002] The rapid development of flexible sensors such as smart wearable devices has expanded the demand for flexible strain sensing materials. Ideal flexible strain sensing materials should have excellent mechanical properties and highly sensitive electrical response to meet the needs of strain monitoring in different application scenarios.
[0003] Existing flexible strain sensing materials such as conductive polymer materials have good flexibility, but their mechanical strength is often affected while maintaining high sensitivity. Moreover, the compatibility between traditional conductive fillers and flexible matrices is poor, which can easily lead to the attenuation of sensing performance. Therefore, it is urgent to develop new flexible sensing composite materials with excellent mechanical properties and high-sensitivity electrical response. In recent years, conductive hydrogels have attracted widespread attention in the field of flexible strain sensing due to their unique three-dimensional network structure and excellent mechanical properties. Researchers have prepared a series of conductive hydrogel composites by introducing conductive fillers such as metal nanoparticles and carbon nanomaterials into the hydrogel matrix. However, although the introduction of a large number of conductive fillers improves the sensitivity of the material, it also inevitably affects the mechanical properties of the composite material. At the same time, the weak interaction between the conductive filler and the hydrogel matrix limits the long-term stability and fatigue resistance of the sensing material.
[0004] Therefore, developing a new type of flexible sensing composite material system that can achieve high-sensitivity electrical response and accurate monitoring of multiple strain signals while ensuring excellent mechanical properties is of great significance for expanding the application scope of flexible strain sensing materials and promoting the advancement of flexible sensor technologies such as smart wearable devices and electronic skin. Summary of the invention
[0005] In order to solve the above technical problems, the present invention provides a high-sensitivity flexible sensing composite material and a preparation method thereof, wherein the preparation method comprises the following steps: Step 1: Preparation of a substrate for a highly sensitive flexible sensing composite material: Add sodium carboxymethyl cellulose to deionized water, stir at room temperature for 15-20 minutes to prepare CMC solution, and perform ultrasonic treatment for 15-20 minutes; Add polyvinyl alcohol powder, CMC solution and dimethyl sulfoxide into a round-bottom flask in sequence, stir for 2.5-3 hours in an oil bath at 140-150°C, and cool to 40-50°C to obtain a PVA-CMC hydrogel reaction solution; Pour the PVA-CMC hydrogel reaction solution into the low-temperature 3D printer extruder, adjust the bottom plate temperature to -20°C, start low-temperature 3D printing, cool for 5-7 minutes after printing, remove the sample and place it in a -18°C environment for 24 hours, thaw at room temperature for 2-2.5 hours, and then soak the sample in deionized water for 3-4 days, replace the deionized water every 12 hours, and obtain the matrix of the high-sensitivity flexible sensing composite material with a preset structure - PVA-CMC hydrogel; Step 2: Conductive functionalization of PVA-CMC hydrogel: Prepare a 0.1-2.0M silver nitrate solution, a 10% polyvinyl pyrrolidone solution, and a 0.02-0.15M ascorbic acid solution; Mixing equal volumes of ascorbic acid solution and polyvinyl pyrrolidone solution as reducing agent solution, and mixing equal volumes of silver nitrate solution and polyvinyl pyrrolidone solution as reducing agent solution; The PVA-CMC hydrogel is immersed in a reducing agent solution for 8-10 hours, then transferred to a reducing agent solution and immersed for 24 hours, and the residual solution is taken out and dried to obtain a highly sensitive flexible sensing composite material with a dense silver particle layer reduced on the surface.
[0006] A high-sensitivity flexible sensing composite material prepared by a preparation method thereof has high mechanical strength, high conductivity, high sensitivity and a wide strain response range, and is suitable for strain sensing in the fields of smart wearable devices, electronic skin and soft robots.
[0007] Beneficial effects of the present invention: The flexible sensing composite material involved in the present invention uses PVA and CMC as matrix materials. The abundant hydroxyl groups in PVA and the negatively charged carboxyl groups in CMC interact with each other through hydrogen bonds to form a stable three-dimensional network structure. At the same time, the introduction of DMSO promotes the crystallization and interchain interaction of PVA, further enhancing the mechanical strength of the hydrogel. Therefore, the composite material prepared by the present invention lays a solid foundation for achieving high-sensitivity sensing while ensuring excellent mechanical properties.
[0008] The present invention adopts a solution immersion reduction method, and utilizes the microstructure and abundant active functional groups of the PVA-CMC hydrogel to enable silver ions to be firmly bound to the hydrogel matrix through coordination, electrostatic adsorption, and the like. After in-situ reduction by a reducing agent, a dense and uniform silver particle conductive layer is formed on the surface of the hydrogel. The entire reduction process is fast and stable, and the multiple interactions between the silver particles and the functional groups ensure the long-term stability of the conductive layer. Thanks to this conductive functionalization strategy, the composite material prepared by the present invention obtains excellent conductive properties and highly sensitive electrical response.
[0009] The composite material prepared by the present invention exhibits excellent strain monitoring performance. The material has a high-sensitivity gauge factor and a fast response characteristic, and can sensitively monitor strain signals caused by tiny masses or deformations. In addition, a variety of structures can be achieved through low-temperature 3D printing technology, further improving the composite material's ability to accurately monitor strain signals. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 The rheological diagram of the flexible sensing composite material matrix of the present invention; Figure 2 This is a physical picture of the flexible sensing composite material of the present invention; Figure 3 This is a super-well depth map of the upper surface of the flexible sensing composite material of the present invention; Figure 4 Phase diagram of the flexible sensing composite material with different structures of the present invention; Figure 5 It is the stress-strain diagram of the flexible sensing composite material of the present invention; Figure 6 It is a sensitivity diagram of the flexible sensing composite material of the present invention; Figure 7 This is a cyclic stretch sensing signal diagram of the flexible sensing composite material of the present invention; Figure 8 This is a sensor signal diagram of the flexible sensing composite material of the present invention when monitoring blowing and pulse. DETAILED DESCRIPTION
[0011] This embodiment provides a method for preparing a high-sensitivity flexible sensing material with adjustable sensing sensitivity, comprising the following steps: Step 1: Preparation of a substrate for a highly sensitive flexible sensing composite material: Add sodium carboxymethyl cellulose to deionized water, stir at room temperature for 15-20 minutes to prepare CMC solution, and perform ultrasonic treatment for 15-20 minutes; Add polyvinyl alcohol powder, CMC solution and dimethyl sulfoxide into a round-bottom flask in sequence, stir for 2.5-3 hours in an oil bath at 140-150°C, and cool to 40-50°C to obtain a PVA-CMC hydrogel reaction solution; Pour the PVA-CMC hydrogel reaction solution into the low-temperature 3D printer extruder, adjust the bottom plate temperature to -20°C, start low-temperature 3D printing, cool for 5-7 minutes after printing, remove the sample and place it in a -18°C environment for 24 hours, thaw at room temperature for 2-2.5 hours, and then soak the sample in deionized water for 3-4 days, replace the deionized water every 12 hours, and obtain the matrix of the high-sensitivity flexible sensing composite material with a preset structure - PVA-CMC hydrogel; Step 2: Conductive functionalization of PVA-CMC hydrogel: Prepare a 0.1-2.0M silver nitrate solution, a 10% polyvinyl pyrrolidone solution, and a 0.02-0.15M ascorbic acid solution; Mixing equal volumes of ascorbic acid solution and polyvinyl pyrrolidone solution as reducing agent solution, and mixing equal volumes of silver nitrate solution and polyvinyl pyrrolidone solution as reducing agent solution; The PVA-CMC hydrogel is immersed in a reducing agent solution for 8-10 hours, then transferred to a reducing agent solution and immersed for 24 hours, and the residual solution is taken out and dried to obtain a highly sensitive flexible sensing composite material with a dense silver particle layer reduced on the surface.
[0012] A high-sensitivity flexible sensing composite material prepared by a preparation method thereof has high mechanical strength, high conductivity, high sensitivity and a wide strain response range, and is suitable for strain sensing in the fields of smart wearable devices, electronic skin and soft robots.
[0013] Effect analysis: Based on the preparation method, the present invention successfully prepared the reaction liquid of the matrix material of the flexible sensing composite material. The viscosity of the matrix material reaction liquid gradually decreases with the increase of shear rate, and has shear thinning characteristics. At the same time, the storage modulus and dissipation modulus increase with the decrease of temperature, and there is a liquid-gel transition point, such as Figure 1 The rheological characteristics shown in the figure indicate that as the temperature decreases and is maintained at -20 °C, the base material of the flexible sensing material can be smoothly formed by low-temperature 3D printing technology, providing a material basis for the subsequent realization of the conductive-sensing function. After the base material undergoes the in-situ silver reduction process, the silver layer exists on the surface of the base material of the flexible sensing composite material, such as Figure 2 As shown in Figure 2, the flexible sensing composite material is first formed into a substrate and then functionalized for conductivity, so the structure of the substrate surface is retained, such as Figure 3 As shown, this shows that the flexible sensing composite material can take into account both structure and function. The surface phase results of the flexible sensing composite material show that the silver layer on the surface of the sample is single silver (such as Figure 4 ), which provides a functional basis for high-sensitivity sensing function.
[0014] The present invention designs different surface structures of the flexible sensing composite material, and the flexible sensing composite material under various structural conditions has good mechanical strength and is higher than the flexible composite material formed by the mold under the same conditions (such as Figure 5 ). The flexible sensing composite material with a surface structure of 15° has high mechanical strength. Good mechanical strength provides a good mechanical strength foundation for its stable and reliable sensing function application. Under the composite effect of the flexible matrix and the single silver layer, the flexible sensing composite material has a sensitivity gauge factor of 31 and has high sensitivity characteristics, such as Figure 6 As shown. Under different strain cyclic stretching conditions, the flexible sensing composite material exhibits stable strain sensing function ( Figure 7 ) and good fatigue resistance. At the same time, the flexible sensing composite material can effectively monitor the strain signals caused by blowing and pulse in real time, verifying its high sensitivity characteristics.
Claims
1. A method for preparing a highly sensitive flexible sensing composite material, characterized in that: The following steps are involved: Step 1, prepare the matrix of the high-sensitivity flexible sensing composite material: Add sodium carboxymethyl cellulose to deionized water, stir at room temperature for 15-20 minutes to obtain CMC solution, and ultrasonically treat for 15-20 minutes; Add polyvinyl alcohol powder, CMC solution, and dimethyl sulfoxide to a round-bottom flask in sequence, stir for 2.5-3 hours in an oil bath at 140-150°C, and cool to 40-50°C to obtain a PVA-CMC hydrogel reaction solution; Pour the PVA-CMC hydrogel reaction solution into the low-temperature 3D printer extruder, adjust the bottom plate temperature to -20°C, start low-temperature 3D printing, cool for 5-7 minutes after printing, remove the sample and place it in a -18°C environment for 24 hours, thaw at room temperature for 2-2.5 hours, and then soak the sample in deionized water for 3-4 days, replace the deionized water every 12 hours, and obtain a matrix of a high-sensitivity flexible sensing composite material with a preset structure - PVA-CMC hydrogel; Step 2. Conductive functionalization of PVA-CMC hydrogel: prepare a silver nitrate solution with a concentration of 0.1-2.0M, a polyvinyl pyrrolidone solution with a mass fraction of 10%, and an ascorbic acid solution with a concentration of 0.02-0.15M; mix equal volumes of the ascorbic acid solution and the polyvinyl pyrrolidone solution as the reducing agent solution, and mix equal volumes of the silver nitrate solution and the polyvinyl pyrrolidone solution as the reducing agent solution; soak the PVA-CMC hydrogel in the reducing agent solution for 8-10 hours, then transfer it to the reducing agent solution and soak it for 24 hours, take out and absorb the residual solution to obtain a high-sensitivity flexible sensing composite material with a dense silver particle layer reduced on the surface.
2. The method for preparing a highly sensitive flexible sensing composite material according to claim 1, characterized in that: The mass ratio of CMC to PVA is 3:97, and the volume ratio of dimethyl sulfoxide to deionized water is 80:
20.
3. A high-sensitivity flexible sensing composite material prepared by the method for preparing a high-sensitivity flexible sensing composite material according to any one of claims 1 to 2, characterized in that: The material has high mechanical strength, high conductivity, high sensitivity and a wide strain response range, and is suitable for strain sensing in the fields of smart wearable devices, electronic skin and soft robots.