Extended bandwidth of 2DOF double impact triboelectric energy harvesting: Theoretical and experimental verification

Increasing the bandwidth of the vibrational energy harvesters is one of the research emphases to maximize the energy harvested from the ambient. Here we design a Two-Degree of Freedom (2DOF) Vibro-impact Triboelectric Energy Harvester with a double impact configuration, which combines multi-modality and piecewise linearity to improve the harvesting bandwidth of triboelectric energy harvesters. The harvester structure consists of a primary cantilever beam attached to a secondary cantilever beam through a tip mass opposite the primary beam. The tip of each beam was designed to act as a multi-layers triboelectric energy harvester. When the system is subjected to a base excitation, the beams will vibrate, resulting in an impact between the triboelectric layers, and an alternating electrical signal is generated. The two beams are designed to have close natural frequencies, and under the effect of the impact, the bandwidths of the resonators are combined to create a wide bandwidth, hence increasing the efficiency of the energy harvester. A theoretical 2DOF lumped parameter model was developed to extract the governing equations of the double impact system. A simulation analysis was conducted to examine the structure’s dynamic behavior at different excitation levels, separation distance, and surface charge density to extract an optimal parameter for combining beams’ bandwidths. A wide bandwidth of 23 Hz was achieved at an excitation frequency of 0.7 g. Finally, experimental results were extracted to validate the simulation results. The system demonstrates the capability of connecting multi-modality and piecewise linearity to significantly broaden the bandwidth of the triboelectric energy harvester for scavenging ambient vibrations over a wide range of excitation frequencies.