Flexible piezoelectric energy generators based on P(VDF-TrFE) nanofibers

Developing flexible/stretchable piezoelectric nanogenerators (PNGs) for powering various portable wearable electronic devices has attracted considerable attention. In this study, we investigate the effects of changing the degree of alignment and thermal annealing conditions on the mechanical properties and the performances of the polymer nanofiber PNGs. PNGs are fabricated with electrospun poly(vinylidenefluoride-cotrifluoroethylene) (P(VDF-TrFE)) nanofibers under various rolling and thermal annealing posttreatment conditions. Thermal annealing increases both the ferroelectric phase and the modulus of the nanofibers, and geometrically aligned nanofibers show anisotropic changes in modulus, stiffer in parallel direction stretching. The performances of PNGs fabricated under various conditions are compared, and the mechanism by which the mechanical properties are affected by the degree of alignment and thermal annealing is analyzed and discussed. The well-aligned and thermally treated PNG cells showed the increased power density value of 1.35 mW cm^-3 which is twice of the pristine randomly oriented samples without thermal treatment. Also, the nanofibers maintained its alignment structure after 10,000 times cyclic 7% stretching test without any cracks.