A Short-Stroke Electrostatic Vibrational Energy Harvester with Extended Bandwidth and Sensitivity

A design strategy is presented to simultaneously enhance the bandwidth and the sensitivity of electrostatic vibrational energy harvester without excessively depending on the velocity amplification through mechanical resonance. Instead, the new design uses comb-electrodes of very short-stroke that are finished with an extremely high density electret film, thereby enhancing the mechano-electric power conversion efficiency, leading to a 3.6-fold expansion of frequency bandwidth from 18 Hz to 64 Hz around a center frequency of around 100 Hz when the electret potential is 1.5-fold enhanced from −200 V to −300 V. Normalized power density as large as $700 \mu \mathrm{W}/\text{cm}^{3}/\mathrm{G}^{2}$ is confirmed.