Polydimethylsiloxane-V2C MXene-based conductive elastomer composites for piezoresistive sensor applications

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Abstract Flexible pressure sensors have potential applications in biomedical and human machine interfaces. Recently, one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) conductive filler-based conductive elastomer composites (CECs) have been widely researched for pressure sensing applications. Among all the fillers, 2D and 1D conductive fillers showed promise for sensing due to the increased directional electrical conductivity within the filler materials. To continue the search for better 2D conductive fillers to prepare high-sensitivity piezoresistors, polydimethylsiloxane (PDMS)-V2C composite-based piezoresistors were fabricated, and the parameters of the flexible resistance pressure sensors (fRPSs) were evaluated. High-quality V2C MXenes were prepared by standard Al layer etching from the V2AlC compound using hydrofluoric acid at 50 ∘C. The phase purity, surface chemical properties, and morphology of the as-synthesized V2C were characterized by x-ray diffraction, Fourier-transformed infrared spectrum, micro-Raman spectrum, x-ray photoelectron spectrum, thermogravimetric analysis, and transmission electron tunneling nanoscope. The PDMS-V2C composites were made by blending 60, 70, and 80 mass% of V2C MXenes with a fixed mass of PDMS matrix and spin coating to make sensing films. The elastic modulus and tensile strength of the pure PDMS and CECs were studied using the universal tensile stress–strain curve. Pressure sensors were made by keeping the piezoresistance CEC on conductive interdigital electrodes (on polyethylene terephthalate substrate) and the resistance was measured in shunt mode. The sensor characteristics of pressure sensitivity, response and relaxation time, output stability, and durability of the sensor under cyclic loading were studied for the fabricated fRPSs. Among the piezoresistors studied, the PDMS-70 mass% V2C composite-based fRPS showed a high sensitivity of 0.32 kPa−1 in the 0–3 kPa pressure range with a response and recovery time of 416 and 413 ms, respectively. The 60 and 80 mass% V2C filler content CECs showed a sensitivity of 0.005 and 0.03 kPa−1 in the 0–3 kPa range, respectively. The sensor was tested for real-life applications.