A Full Polymer Piezoelectric Flextensional Energy Harvester

This study presents a full polymer piezoelectric flextensional energy harvester (FPPFEH) comprising a single-layer poly(vinylidene fluoride) (PVDF) film bonded to a 3D-printed polylactic acid (PLA) flextensional frame. For an arm inclination angle of θ=10°, the free-body model gives a theoretical geometric force-amplification factor of MF=cotθ≈5.67; this value represents an ideal upper bound and was not independently validated by local force or strain measurements. During assembly, the film was tensioned only to remove visible slack and maintain a flat configuration. No intentional pretension was applied, and any residual tension was not measured. Off-resonance force-controlled tests showed that the generated voltage was approximately proportional to the dynamic input force and nearly independent of frequency after accounting for attenuation caused by the finite measurement-input impedance. The ideal quasi-static model overpredicted the absolute voltage by a nearly constant factor across the tested force range. This offset is consistent with a lumped reduction associated with frame compliance and the in-plane anisotropy of the PVDF film, neither of which was independently measured. At 30Hz and 12.32Nrms, the rectified output charged a 6600μF supercapacitor to 2.10V in 14min, corresponding to 14.55mJ of stored energy. Under base-acceleration excitation from 0.05 g to 1 g, the voltage peak occurred between 112.88 and 116.49Hz, close to the electrical anti-resonance near 114Hz, and reached 12.11Vpeak at 1 g. Near resonance, the highest measured power among the tested resistive loads occurred between 150 and 200kΩ; however, the exact optimal resistance could not be resolved from the four tested loads. These results demonstrate off-resonance force-driven energy storage and resonance-mode vibration energy harvesting within the tested conditions.