Porous graphene/poly(vinylidene fluoride) nanofibers for pressure sensing

Piezoelectric polymers have emerged as promising materials for application in pressure sensing devices in particular for wearable applications, where inorganic piezoelectric materials can face limitations due to their brittleness. One of the bottlenecks for the adaptation of piezoelectric polymers is their relatively weak piezoelectric voltage coefficient. Hence there have been numerous efforts to improve the performance of the comprising devices by making composites of poly(vinylidene fluoride) (PVDF), or through making porous PVDF films, or by nanostructuring. Here, we demonstrate the fabrication of porous nanofibers with graphene/PVDF composites and investigate the suitability of the fiber for motion sensing. The nanofibers are fabricated by electrospinning from the solution phase. Guided by an experimentally validated phase diagram for PVDF/solvent/non-solvent ternary system, porous graphene/PVDF nanofibers with different porosities and pore morphologies have been produced through solidifying the fibers in the binodal or spinodal regions of the phase diagram. It is found that only by solidifying the composite fibers in the spinodal region, graphene loading of 0.1 wt% promotes the formation of the electroactive phase substantially, and the resulting fibers exhibit enhanced piezoelectric output. It is further shown that the comprising sensors are biocompatible and show high sensitivity to body motion.