Enhanced piezoelectric and electrodeformation properties of PVDF films fabricated by roll to roll process

beta-phase poly(vinylidene fluoride) (PVDF) film boasts excellent electrical properties and can be used in sensors, micro actuation, and energy harvesting. In this paper, high beta-phase PVDF films were stretched by stretch-line equipment (roll to roll) and the beta-phase content can reach 60%, realizing the potential for large-scale fabrication. Moreover, the electrical and electrostrictive properties of PVDF films before and after stretching are compared. The stretched film (PVDF-R film) has better piezoelectric properties and electrostrictive properties due to the formation of high beta phase in the stretched film and the directional arrangement of PVDF molecular chains in the amorphous region (the formation of directional amorphous). Under the same driving electric field intensity (180 kV/mm), the electrostrictive deformation of PVDF film is 1.5 mu m, while that of PVDF-R film is 2 mu m. The piezoelectric coefficient of the PVDF-R films can reach 36 pC/N. The output voltage of the PVDF-R film in finger press mode is studied and the peak position of the output voltage signal is obvious, which can be used for pulse monitoring.