Solid-state-processing of δ-PVDF

Poly(vinylidene fluoride) (PVDF) has long been regarded as an ideal piezoelectric 'plastic' because it exhibits a large piezoelectric response and a high thermal stability. However, the realization of piezoelectric PVDF elements has proven to be problematic due to, amongst other reasons, the lack of industrially scalable methods to process PVDF into the appropriate polar crystalline forms. Here, we show that fully piezoelectric PVDF films can be produced via a single-step process that exploits the fact that PVDF can be molded at temperatures below its melting temperature, i.e. via solid-state-processing. We demonstrate that we thereby produce delta-PVDF, the piezoelectric charge coefficient of which is comparable to that of biaxially stretched beta-PVDF. We expect that the simplicity and scalability of solid-state processing combined with the excellent piezoelectric properties of our PVDF structures will provide new opportunities for this commodity polymer and will open a range of possibilities for future, large-scale, industrial production of plastic piezoelectric films.