A packaged electrostatic energy harvester with micro-molded bulk electrets

This paper reports a packaged energy harvester using the novel method of micro-molding bulk electrets of polytetrafluoroethylene (PTFE). Compared with thin film electrets prepared by spin-coating method, bulk PTFE electrets are of higher trapped charge density by 1.2~2 times, and improved charge storage stability by 1.3 times in charge retain rate over 10 days. Further, the micromolding method guarantees high throughput and cost-effectiveness. The proposed harvester is non-resonant and is of gap-closing structure, which is suitable for low frequency vibration. Maximally, the packaged device generates 2.5μW @10Hz, 1.6g vibration, which is 9 times improvement in power compared with our previous thin film PTFE work. Such results display the potential of using micro-molded bulk PTFE electrets for integrated electrostatic energy harvester in low frequency applications.