Dynamic Response and Energy Conversion of Coupled Cantilevers with Dual Piezoelectric-Triboelectric Harvesting Mechanisms.

This study presents a Hybrid Piezoelectric-Triboelectric Energy Harvester (HPTEH) composed of two coupled cantilever beams, designed to enhance energy generation and broaden bandwidth by combining piezoelectric and triboelectric mechanisms. A theoretical 2-DOF lumped model was developed and validated with experimental results, demonstrating good agreement. Experimental findings reveal that Beam I exhibits a softening effect, with resonance frequencies shifting to lower values and increased displacement amplitudes under higher excitation levels due to material nonlinearities and strain-induced voltage generation. Beam II, in contrast, displays a hardening effect, with resonance frequencies increasing as triboelectric interactions enhance stiffness at higher excitation levels. Coupling dynamics reveal asymmetry, with Beam I significantly influencing Beam II in the higher frequency range, while Beam II's impact on Beam I remains minimal. Phase portraits highlight the dynamic coupling and energy transfer between the beams, particularly near their natural frequencies of 18.6 Hz and 40.6 Hz, demonstrating complex interactions and energy exchange across a broad frequency range. The synergistic interplay between triboelectric and piezoelectric mechanisms allows the HPTEH to efficiently harvest energy across a wider spectrum, underscoring its potential for advanced energy applications in diverse vibrational environments.