A capsule-structured triboelectric energy harvester with stick-slip vibration and vibro-impact

Highlights: • A hybrid frictional slider-in-capsule triboelectric energy harvester is proposed. • Mechanical and electrical domains are coupled in a theoretical model. • Complicate non-smooth dynamics and electrical behaviour are studied theoretically. • Impact and chatter are found to enhance output power. • The device is capable of harvesting energy without limitation of bandwidth. Despite great progress made in triboelectric energy harvesting, most investigations are purely about experiments and/or manufacturing. There is a serious lack of in-depth theoretical studies of the underlying vibration and its effects on power yield. In this paper, a novel triboelectric energy harvester is presented and its non-smooth structural dynamics and electrical performance are studied. This first theoretical study of a capsule-structured triboelectric energy harvester includes a mathematical model coupling the structural dynamics and electric dynamics, which integrates in-plane sliding mode and contact-separation mode. The influences of friction properties on sliding surfaces, electrostatic force, initial slider position, excitation level and harvester dimensions, are investigated. The performance of this harvester is not limited by its frequency bandwidth, whose average power increases from 10.3 μW at 3 Hz to 69.4 μW at 14 Hz. Impact/chatter events are found to improve power yield, for example, there is a dramatic increase of 20 μW at 6 Hz due to impact induced by a slight increase of excitation amplitude. Additionally, the internal capsule length plays a subtle role and a length beyond a certain value causes a sharp fall of power yield. These findings enable innovative designs and provide fabrication guidelines of triboelectric energy harvesters.