Ultra-drawn PVDF piezoelectric film for linear and large-range pressure sensing

Abstract

Research on the piezoelectricity of poly(vinylidene fluoride) (PVDF) has primarily concentrated on the β phase content, with comparatively little attention paid to the crystallization morphology of the β phase and the crystalline and amorphous interfaces. Herein, we prepared piezoelectric PVDF films with pure β phase, high crystallinity, and rich crystalline-amorphous interface through ultra-drawing and high-pressure thermal annealing. The solution casting PVDF films exhibited similar to thermotropic glass transition behavior (steps in the DSC curves, Tg-like), resulting in stretching multiplicities up to 12, much higher than previous studies. Meanwhile, the refinement of oriented fiber crystals was visually shown in the AFM force mapping images. Furthermore, the WAXD and SAXS results demonstrated that the PVDF exhibited a smaller grain size following ultra-drawing. The piezoelectric coefficient of the PVDF film subjected to ultra-drawing is superior to that of the commercial PVDF film. Self-powered sensor devices based on PVDF film exhibit excellent linear sensing characteristics over a large stress range (20 MPa). The work presents a straightforward approach for the fabrication of flexible piezoelectric PVDF films, facilitating the commercialization of a vast array of self-powered sensing films.