In-situ poled magneto-mechano piezoelectret nanogenerator for self-powered electronics

The development of next-generation self-powered systems demands multidimensional flexible energy harvesters capable of converting both mechanical and magnetic energies into electrical output. Despite higher performance, the deployment of ceramic magnetoelectric (ME) restricted by their inherent nature of brittleness, toxicity, and environmental unsuitability. The novelty in the present work is the realization of a self-poled porous Poly(vinylidene fluoride)/Nickel oxide (PVDF-NiO) piezoelectret structure with a flexible nanogenerator, where the charge trapping effect due to micropores, the polarization effect at the NiO/PVDF interface, and the effect of strain transfer under magnetic field cooperatively work. The device, fabricated from a porous polyvinylidene fluoride and nickel oxide composite via a simple solvent evaporation method, demonstrates nucleation and local alignment of electroactive β-phase content without requiring external biasing. The porous architecture promotes charge trapping and self-polarization, yielding extremely high piezoelectricity and figure-of-merit (∼ 95.7 × 10⁻¹² Pa⁻¹). This strong piezoelectret response couples with the magnetic properties of nickel oxide leading to the magnetoelectric coupling. This interaction results in a peak magnetoelectric voltage coefficient of 2.4 mV·cm⁻¹ ·Oe⁻¹ . Remarkably, around 80% of this peak value is retained without any external DC magnetic field due to intrinsic self-biasing capability. This self-biased magnetoelectric response, together with the mechanical energy harvesting achieved in the same device, sets apart the present MMFNG from the conventional PVDF based magnetoelectric composites, which typically require external electrical poling and/or finite DC magnetic biasing. Under mechanical excitation, the device generates an open-circuit voltage of 20 V, power density of 13.10 μW·cm⁻ 2 , with an energy conversion efficiency of 84%. These results establish the magnetoelectric composite-based device as a multifunctional and environmentally friendly platform, offering great promise for self-powered electronics and multidimensional sensing technologies.