Flexible piezoelectric energy-harvesting nanogenerator using supersonically sprayed polyvinylidene fluoride and iron oxide nanocubes

Soft wearable electronics are being applied as state-of-the-art self-powered devices based on piezoelectric nanogenerators (PENGs), which provide flexible energy harvesters and sustainable energy generators. We introduce a composite of poly(vinylidene fluoride) (PVDF) and Fe₂O₃ nanocube fillers coated via supersonic cold spraying to obtain substrate-free and flexible films for PENGs. The hydrothermally synthesized Fe₂O₃ nanocubes induce shear stress between Fe₂O₃ and PVDF during supersonic spraying. An optimized sample having 0.77 g Fe₂O₃ in 1 g PVDF produces a piezopotential of 25.6 V and a short-circuit current of 70 μA. In addition, a maximum power density of 44.4 μW·cm⁻² is achieved at a load resistance of 1 MΩ. Tapping and bending tests for 1800 s confirm the consistent generation of piezopotentials of 25.6 V and 1.5 V, respectively. The developed Fe₂O₃/PVDF PENG can power several light-emitting diodes, thus showing promise as a device for sustainable power supply.