A method for fabricating a strain sensor based on graphene / TPU composite material

Abstract

This invention provides a method for preparing a strain sensor based on graphene / TPU composite material. The method involves: freeze-drying and crushing a graphene dispersion to obtain graphene aerogel fragments; adding N,N-dimethylformamide to a thermoplastic polyurethane elastomer and ultrasonically dispersing and dissolving it to obtain a thermoplastic polyurethane elastomer / N,N-dimethylformamide solution; dissolving the graphene aerogel fragments in tetrahydrofuran and ultrasonically dispersing them to obtain a graphene / tetrahydrofuran solution; mixing the thermoplastic polyurethane elastomer / N,N-dimethylformamide solution and the graphene / tetrahydrofuran solution and ultrasonically dispersing them to obtain a mixed dispersion; clamping both ends of a PDMS film with a clamp and stretching it by 5%, then adding the mixed dispersion dropwise, and drying to obtain the graphene / TPU composite material-based strain sensor. The graphene / TPU composite film prepared by this invention exhibits subtle sensing capabilities under external force stimulation, achieving highly repeatable and stable strain sensing.

Description

Technical Field

[0001] This invention belongs to the field of strain sensor technology, specifically relating to a method for preparing a strain sensor based on graphene / TPU composite material. Background Technology

[0002] Flexible wearable sensors have attracted widespread attention due to their enormous potential applications in human-computer interfaces, soft robotics, health monitoring, virtual reality, and human-computer interaction. Among these, achieving non-invasive real-time monitoring of physiological signals is of great significance for personalized medicine and health monitoring. Developing high-sensitivity, low-cost, high-performance flexible wearable strain sensors has become a research hotspot in both scientific research and industry. Flexible strain sensors are typically fabricated by depositing sensitive materials onto the surface of a flexible substrate or encapsulating a sensing layer within a flexible material. Therefore, the sensor's sensing performance primarily depends on the mechanical flexibility of the flexible material and the conductivity of the sensitive material.

[0003] In recent years, thanks to technological innovations in materials science and engineering, the field of flexible strain sensors has made significant progress. Currently, flexible products under research, development, and application, including touch panels, artificial skin, human-machine interfaces, and wearable medical devices, have demonstrated their significant importance. Flexible strain sensors are characterized by high sensitivity, fast response recovery rate, and good stability. To overcome the limitations of traditional deformable materials, designing and improving the performance of flexible sensors is crucial; therefore, employing a corrugated structure design for strain sensor devices is essential for enhancing their performance indicators. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for fabricating a graphene / TPU composite strain sensor. The graphene / TPU composite film prepared by this method exhibits subtle sensing capabilities under external force stimulation, achieving highly repeatable and stable strain sensing.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a strain sensor based on graphene / TPU composite material, the method being as follows:

[0006] S1. The graphene dispersion was freeze-dried at -60℃ for 48h to obtain graphene aerogel. After crushing, graphene aerogel fragments were obtained.

[0007] S2. Add N,N-dimethylformamide to the thermoplastic polyurethane elastomer, and ultrasonically disperse and dissolve for 30 min to obtain a thermoplastic polyurethane elastomer / N,N-dimethylformamide solution.

[0008] S3. Dissolve the graphene aerogel fragments obtained in S1 in tetrahydrofuran and disperse them by ultrasonication for 30 min to obtain a graphene / tetrahydrofuran solution.

[0009] S4. Mix the thermoplastic polyurethane elastomer / N,N-dimethylformamide solution obtained in S2 and the graphene / tetrahydrofuran solution obtained in S3, and ultrasonically disperse for 5 min to obtain a mixed dispersion.

[0010] S5. Clamp both ends of the PDMS membrane with a clamp and stretch it by 5%. Then add the mixed dispersion obtained in S4 and dry it at 80℃ for 30 minutes to obtain a strain sensor based on graphene / TPU composite material.

[0011] Preferably, the ratio of the thermoplastic polyurethane elastomer to N,N-dimethylformamide in S2 is 2g:10mL.

[0012] Preferably, the ratio of graphene aerogel fragments to tetrahydrofuran in S3 is 100 mg: 10 mL.

[0013] Preferably, the PDMS membrane in S4 has a size of 5cm × 1cm; and the amount of the mixed dispersion added is 1mL.

[0014] The application of the graphene / TPU composite strain sensor prepared in this invention is for collecting gesture information from data gloves.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. Graphene possesses many properties particularly suitable for sensor applications, including flexibility, lightweight, excellent electromechanical properties, extremely high transmission characteristics, and significant photoelectric properties, making it highly promising for stress and strain sensing. However, the low strain tolerance of pure graphene and the fragility of pure graphene films greatly limit its application in wearable devices. This invention improves the mechanical strength by adding thermoplastic polyurethane elastomer (TPU). The graphene / TPU composite strain sensor prepared by this invention has advantages such as good stretchability, high sensitivity, simple operation, high stability, and low material and manufacturing costs.

[0017] 2. This invention uses thermoplastic polyurethane elastomer (TPU) as the elastic matrix, providing excellent mechanical properties, including high resilience and high repeatability. Graphene, as the conductive filler in the sensing layer, effectively reduces the device resistance, giving it low-resistance characteristics. The graphene / TPU composite film formed by embedding graphene as a conductive filler within the thermoplastic polyurethane elastomer in this invention exhibits subtle sensing capabilities under external force stimulation. This achieves highly repeatable and stable strain sensing.

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 This is the Fourier transform infrared spectrum of the graphene / TPU composite strain sensor of Embodiment 1 of the present invention.

[0020] Figure 2 This is the XRD pattern of the graphene / TPU composite strain sensor of Embodiment 1 of the present invention.

[0021] Figure 3 This is a mechanical property test diagram of the graphene / TPU composite strain sensor based on the present invention under 1%-5% deformation.

[0022] Figure 4 This is a mechanical repeatability test diagram of the graphene / TPU composite strain sensor based on the present invention under 4% deformation, according to Embodiment 1 of the present invention.

[0023] Figure 5 This refers to the changes in current values ​​during the 0th-6th response cycle and the 90th-96th deformation cycle of the graphene / TPU composite strain sensor based on 4% deformation in Embodiment 1 of the present invention. Detailed Implementation

[0024] Example 1

[0025] The method for fabricating a graphene / TPU composite strain sensor in this embodiment is as follows:

[0026] S1. The graphene dispersion was freeze-dried at -60℃ for 48h to obtain graphene aerogel. After crushing, graphene aerogel fragments were obtained.

[0027] The graphene dispersion is commercially available.

[0028] S2. Add 10 mL of N,N-dimethylformamide (DMF) to 2 g of thermoplastic polyurethane elastomer (TPU), and sonicate and dissolve for 30 min to obtain thermoplastic polyurethane elastomer / N,N-dimethylformamide solution, abbreviated as TPU / DMF solution;

[0029] The thermoplastic polyurethane elastomer is commercially available;

[0030] S3. Dissolve 100 mg of the graphene aerogel fragments obtained in S1 in 10 mL of tetrahydrofuran (THF) and sonicate for 30 min to obtain a graphene / tetrahydrofuran solution.

[0031] S4. Mix the thermoplastic polyurethane elastomer / N,N-dimethylformamide solution obtained in S2 and the graphene / tetrahydrofuran solution obtained in S3, and ultrasonically disperse for 5 min to obtain a mixed dispersion.

[0032] S5. Cut the PDMS membrane into 5cm×1cm pieces, clamp both ends with a clamp, stretch it by 5%, and then add 1mL of the mixed dispersion obtained in S4. Dry it at 80℃ for 30min to obtain a strain sensor based on graphene / TPU composite material; the PDMS membrane is commercially available.

[0033] This embodiment also provides an application of the graphene / TPU composite material strain sensor prepared above, which is used for data acquisition of hand gesture recognition data from data gloves.

[0034] The wires were fixed to both ends of the graphene / TPU composite strain sensor prepared in this embodiment using conductive copper tape, and the strain signal was acquired and processed using an Arduino UNO development board.

[0035] This embodiment uses a graphene strain sensor (without thermoplastic polyurethane elastomer) as a comparative example. The specific preparation method is as follows:

[0036] Graphene dispersion was freeze-dried at -60℃ for 48 h to obtain graphene aerogel, which was then broken up to obtain graphene aerogel fragments. 100 mg of the graphene aerogel fragments obtained from S1 was dissolved in 10 mL of tetrahydrofuran (THF) and ultrasonically dispersed for 30 min to obtain a graphene / tetrahydrofuran solution. The PDMS membrane was cut into 5 cm × 1 cm pieces, clamped at both ends, stretched by 5%, and then 1 mL of the mixed dispersion was added dropwise. The membrane was dried at 80℃ for 30 min to obtain a graphene strain sensor.

[0037] like Figure 1 The image shows the FTIR spectra of a comparative graphene strain sensor and a graphene / TPU composite strain sensor prepared in this embodiment. It is readily apparent that the peak positions shift after the introduction of TPU into the graphene. The peak at 3326 cm⁻¹ corresponds to the tensile vibration of the N–H bond; a peak appears at 2952 cm⁻¹ due to the olefin-CH tensile vibration; and a peak appears at 1075 cm⁻¹ due to the C–O–C tensile vibration. Furthermore, the characteristic peak at 1730 cm⁻¹ is attributed to the free C=O bond. Figure 2 As shown, the XRD pattern reveals a characteristic peak at 2θ = 26.4°, corresponding to the crystal plane of graphene. Figure 1 and Figure 2This proves that graphene and TPU are combined together.

[0038] like Figure 3 As shown, the graphene / TPU composite strain sensor prepared in this embodiment maintains high repeatability under deformation of 1%-5%.

[0039] like Figure 4 As shown, the graphene / TPU composite strain sensor prepared in this embodiment remained essentially unchanged in length after 600 repeated stretching cycles at a strain of 4%. The figures show the 50th-60th and 570th-580th cycles, respectively.

[0040] like Figure 5 As shown, the strain sensor based on graphene / TPU composite material prepared in this embodiment was tested for changes in electrical performance under a strain of 4%. The figure shows the 20th-25th and 90th-95th cycles. After 100 repeated tests, the sensor's performance showed almost no change, demonstrating good repeatability.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a graphene / TPU composite material strain sensor, characterized in that, The method comprises: S1, freeze-drying the graphene dispersion liquid at a temperature of-60 DEG C for 48h to obtain graphene aerogel, and crushing to obtain graphene aerogel fragments; S2, adding N, N-dimethylformamide to the thermoplastic polyurethane elastomer, ultrasonic dispersion dissolving for 30min to obtain a thermoplastic polyurethane elastomer / N, N-dimethylformamide solution; the amount ratio of the thermoplastic polyurethane elastomer and N, N-dimethylformamide in S2 is 2g:10mL; S3, dissolving the graphene aerogel fragments obtained in S1 in tetrahydrofuran, ultrasonic dispersion for 30min to obtain a graphene / tetrahydrofuran solution; the amount ratio of the graphene aerogel fragments and tetrahydrofuran in S3 is 100mg:10mL; S4, mixing the thermoplastic polyurethane elastomer / N, N-dimethylformamide solution obtained in S2 and the graphene / tetrahydrofuran solution obtained in S3, ultrasonic dispersion for 5min to obtain a mixed dispersion liquid; S5, clamping both ends of the PDMS film with a clamp and stretching by 5%, then dropping the mixed dispersion liquid obtained in S4, drying at a temperature of 80 DEG C for 30min to obtain a graphene / TPU composite material-based strain sensor; the graphene / TPU composite material-based strain sensor is used for data glove gesture information acquisition.

2. The preparation method of the graphene / TPU composite material strain sensor according to claim 1, characterized in that, The size of the PDMS film in S4 is 5cm*1cm; the amount of the mixed dispersion liquid dropped is 1mL.

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