Ionic Liquid Assisted α–γ′ Phase Transition of Poly(vinylidene fluoride) Thin Films

Multi-functional polyvinylidene fluoride/sodium alginate/SiC/MgCl2 composite film for self-powered humidity and pressure sensing

Self-powered sensors that integrate the power source with the sensing body are extremely appealing in the rapidly developing internet of things (IOTs) like wearable electronics. Multi-function is an even higher level of demand for those related application scenarios. Herein, we reported a composite film that combines the piezoelectric effect of polyvinylidene fluoride with moisture-sensitive materials. The prepared polyvinylidene fluoride/sodium alginate/SiC/MgCl2 composite (PSSM) film showed versatile self-powered sensing functions as battery-typed humidity sensor, piezoelectric pressure sensor, and battery-typed pressure sensor. The PSSM humidity sensor exhibited satisfying response/recovery time (11 s and 17 s from relative humidity of 11% to 98%) and long-term stability. The PSSM-based pressure sensor actuated by piezoelectric and primary battery principle demonstrated significantly improved response of 477% and 1944% that of the pure polyvinylidene fluoride, respectively. The sensing mechanism of the PSSM-based humidity and pressure sensor is explored by complex impedance spectrum and phase angle-frequency curves. The ionization of conductive ions induced by water molecules in the composite film played pivital role in both the humidity and pressure sensing process. Besides, the pressure sensor can self-powered effectively in versatile connection modes. Benefiting from its excellent sensitivity and fast response/recovery, the humidity sensor can be used for human respiration monitoring, and non-contact sensing. And the pressure sensor with the same PSSM sensing film showed use potential in human-machine interaction like Morse-coded communication. The combination of different self-powering principles proposed in this work provides a new way for the development of multi-functional self-powered sensors.