Piezoelectric and magnetoelectric evaluations on PVDF/CoFe 2 O 4 based flexible nanogenerators for energy harvesting applications

In this study, flexible PVDF/CoFe 2 O 4 based nanogenerators were fabricated using composite fibers which were prepared by combining polyvinylidene difluoride (PVDF) and cobalt ferrite (CoFe 2 O 4 ) nanoparticles (NPs: ~16 nm diameter) at a concentration of 1, 3, 5, 7, and 10 wt%. All of the flexible PVDF/CoFe 2 O 4 nanofibers were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The incorporation of CoFe 2 O 4 NPs into the PVDF leads to the formation a rich electroactive β-phase in the composite structure. The piezoelectric properties of nanogenerators indicate that the nanogenerator based on the PVDF/CoFe 2 O 4 fibers containing CoFe 2 O 4 NPs at a concentration of 3 wt% has a greater power efficiency of 27.2% at 20 Hz compared to that of the nanogenerator with the pure PVDF fibers at 10 Hz, under the same resistive load of 2.5 MΩ. The results also show the magnetoelectric properties of the nanogenerator with PVDF + 10 wt% CoFe 2 O 4 reached the highest voltage value of 18.87mV at the same load resistive load (2.5 MΩ) for a low-level magnetic field frequency of 50 Hz. The specially improved nanogenerators which have capability of producing electrical signals at the same time from mechanical and magnetic stimulations hold promise for the development of wearable electronics devices.