An electrospun PVDF-KNN nanofiber based lead-free piezoelectric nanogenerator for mechanical energy scavenging and self-powered force sensing applications

In the era of smart sensors and connected society, flexible piezoelectric nanogenerators (PENGs) are potential candidates, which find applications in self-powered devices, mechanical energy scavenging, electronic skin, human–machine interfaces and health monitoring. Herein, we present the fabrication of a high-performance flexible PENG based upon electrospun PVDF-KNN nanofibers (FPVDF-nKNN). Interestingly, on addition of 10 wt% ferroelectric KNN nanoparticles, which were synthesized via a facile solid-state route accompanied by high energy ball milling into the host PVDF matrix, the electroactive β-phase turned out to be increased to 82% with enhanced crystallinity (∼46%). As a result of the synergic association between the ferroelectric KNN nanoparticles and PVDF, the fabricated PENG has exhibited a high electrical output with an open-circuit voltage of ∼25 V and a short-circuit current density of 5 mA m−2 which is ∼10 fold greater than that of the pristine PVDF nanofibers. Furthermore, the PENG has been demonstrated to be a self-powered force sensor with an excellent sensitivity of ∼3 V/N for low input forces (<10 N) and ∼1.6 V/N in the higher force regime (10 N to 100 N) with a remarkable force resolution of 0.05 N.