An eco-friendly and highly sensitive loofah@CF/CNT 3D piezoresistive sensor for human activity monitoring and mechanical cotrol

Abstract

Three-dimensional (3D) porous piezoresistive sensors are widely used because of their simple fabrication and convenient signal acquisition. However, because of the dependence on organic skeleton materials and the complexity of conductive coating preparation, the electrical and mechanical properties of 3D wearable piezoresistive sensors have gradually failed to accommodate many emerging fields. Here, a new flexible 3D piezoresistive sensor (NF3PS) with high sensitivity and a wide measurement range is proposed, which comprises a natural porous loofah as a flexible framework and carbon fiber/carbon nanotube (CF/CNT) multiscale composite as a conductive coating. Composed of cellulose and lignin, the irregular, porous loofah has excellent mechanical strength, elasticity, and toughness, ensuring a repeated compression/recovery behavior of the NF3PS. In addition, compared with the single-size carbon coating, the coupling of multiscale CF/CNT composite coating improves sensitivities over a range of pressures. The NF3PS demonstrates a sensitivity of 6.94 kPa−1 with good linearity in the pressure range of 0–11.2 kPa and maintains a sensitivity of 0.28 kPa 1 in an ultrawide measurement range of 11.2–84.6 kPa. Considering flexibility, robustness, and wide-ranging linear resistance variation, the feasibility of the NF3PS in human activity monitoring, mechanical control, and smart homes is verified. This work provides a novel strategy for a new generation of 3D flexible pressure sensors for improving sensitivity and measurement range and demonstrates attractive applications in wearable sensors.