Toward High-Performance Wrist-Worn Energy Harvester via Hybrid Approach

We propose a hybrid approach to enhance the power generation performance of wrist-worn energy harvester. Based on a highly compact framework, the energy harvester integrates a planetary gear system to increase energy conversion capacity, an asymmetric carrier to improve motion capacity, and a magnetic spring to enhance displacement and velocity responses. These power enhancement mechanisms work together to boost the output power of the energy harvester. We develop an analytical model to theoretically investigate the effects of different power enhancement mechanisms. A miniature prototype with a total volume of 2.01 cm3is fabricated and tested under bench-top excitations. The experiments include air gap determination of the magnetic spring and measurement of output power for various power enhancement configurations. It is found that the planetary gear system improves the power of conventional wrist-worn energy harvester by 335%–1422%. Based on this, the asymmetric carrier and magnetic spring can further increase the power by 35%–373% and 16%–278%, respectively. If hybridizing the power enhancement mechanisms, the output power can reach 8–28 times that of the conventional structure and the maximum power achieves 326.27±17.46μW at 1.2 Hz.