A high performance capacitive flexible pressure sensor based on three-dimensional porous rGO/PDMS composite

Capacitive flexible pressure sensors have been widely used in the fields of human motion monitoring and wearable electronic devices due to their simple structure, swift response, and easy integration. However, it remains a significant challenge to develop capacitive flexible pressure sensors with high linearity and sensitivity in a wide working range. Inspired by the compound structure of human bones and soft tissues, this paper presents a novel capacitive flexible pressure sensor based on three-dimensional porous rGO/PDMS composite. A polyurethane (PU) sponge coated with graphene oxide (GO) was exposed to an ethanol flame to remove the sponge matrix and reduce the GO. Then polydimethylsiloxane (PDMS) was encapsulated onto the prepared 3D porous conductive graphene to form a hierarchical core-shell structured rGO/PDMS composite. In this configuration, rGO skeleton provides strength and conductivity while PDMS sheath supplies flexibility and elasticity, which synergistically makes it an ideal sensing material for flexible pressure sensors. The prepared rGO/PDMS composite material was sandwiched between two copper foil electrodes as a dielectric layer to form a capacitive flexible pressure sensor. Performance tests demonstrate that the fabricated sensor exhibits a sensitivity of 0.864 kPa-1, a high stability over 2000 cycles, and a rapid response time of 20 ms. Meanwhile, the sensor achieves excellent linearity (R2 = 0.997) within the pressure range of 50-275 kPa. Based on excellent sensing performance, the sensor can be successfully used in monitoring activities and joint movements, demonstrating its broad application potential in wearable devices and human health monitoring.