Piezoelectric Polyacrylonitrile Nanofiber Film-Based Dual-Function Self-Powered Flexible Sensor.

To meet the growing demands in flexible and wearable electronics, various sensors have been designed for detecting and monitoring the physical quantity changes. However, most of these sensors can only detect one certain kind of physical quantity based on a single mechanism. In this paper, we have fabricated a multifunctional sensor made from carbonized electrospun polyacrylonitrile/barium titanate (PAN-C/BTO) nanofiber film. It can detect two physical quantities (pressure and curvature), independently and simultaneously, by integrating piezoresistive, piezoelectric, and triboelectric effects. For flex sensing with the impedance change of PAN-C/BTO nanofiber films during bending, it had a sensitivity of 1.12 deg ^-1 from 58.9° to 120.2° and a working range of 28°-150°. For self-powered force sensing, it had a gauge factor of 1.44 V·N ^-1 within the range of 0.15-25 N. The sensor had a long stability over 60 000 cycles at both sensing modes. The inclusion of barium titanate nanoparticles (BTO NPs) into the nanofiber film had an over 2.4 times enhancement of sensitivity for pressure sensing because of the synergy of piezoelectric and triboelectric effects. On the basis of multifunction and modularity, a series of potential applications of the sensor were demonstrated, including sensing human's swallowing, walking gaits, finger flexure, and finger-tapping. The self-powered flexible dual-mode sensor has great application potential in human-computer interactive and smart wearable sensing systems.