Oscillatory magnetic piezoelectric nanogenerators under low-frequency and low-amplitude excitations

This study reports the oscillatory magnetic piezoelectric nanogenerators (OM-PENG) that use magnetic interaction in the oscillatory structure for energy harvesting under low-frequency and low-amplitude excitations. The OM-PENG are designed with the driving and driven magnets in a magnet-magnet coupled system and the driving magnet and driven mass in the magnet-mass coupled system, such that to efficiently convert oscillation (i.e., mechanical energy) into voltage (i.e., electrical energy). The OM-PENG prototypes are fabricated using 3D printing, and the cantilevered polyvinylidene fluoride (PVDF) strips are bonded with the tip-driven magnets/masses. Experiments are conducted to investigate the OM-PENG with the single and multiple PVDF strips in terms of the output voltage and electrical power. Numerical simulations are carried out to validate the experiments while comparing the magnetic field intensity (MFI) trends. Satisfactory agreements are obtained between the experimental and numerical results. The findings indicate that the maximum output electrical power of approximately 250 µW is obtained for the quadruple OM-PENG (i.e., four PVDF strips) under the constant angular displacement of α=60° and the oscillatory rate of 1.5 Hz. The reported OM-PENG can be applied to harvest energy to power small devices under low-frequency and low-amplitude excitations such as ocean waves.