A vibro-impact triboelectric energy harvester with a magnetic bistable mechanism and grating-patterned films for dual power enhancement

Currently, in the field of triboelectric energy harvesting, there have been extensive studies of material science and manufacturing aspects, but much less on structural vibration aspect, especially for grating-structured triboelectric energy harvesters. This paper presents an in-depth theoretical and experimental investigation on both the structural and electrical dynamics of a novel triboelectric energy harvester, which contains grating-patterned films and a magnetic bistable mechanism for dual enhancement of power yield. It operates in the in-plane sliding mode. Friction is heavily involved during the oscillation of the slider of the harvester, and vibro-impact is likely to occur. A mechanical model of the harvester is established, which covers friction, magnetic force and impact. Based on the film geometry, an electrical model is built accordingly. Numerical simulations are carried out to investigate the effects of the potential wells created by the magnets, acceleration amplitude of excitation, segment number of the grating-patterned films, from the perspectives of both structural and electrical dynamics. The bistable mechanism is proved to shift the frequency band of the harvester to lower frequency values, which is nearly twice as wide as that of the same harvester without this mechanism. When the vibration amplitude of the oscillator is smaller than the width of the grating units on the films, increasing the segment number can dramatically enhance the output voltage. Once the vibration amplitude exceeds the width of the units, the output voltage rises slowly with the increase of the segment number. Harvesters having three types of films with different segment numbers (0, 1 and 2) are made and tested. The root-mean-square output voltage is found to increase from 0.82 V to 3.88 V at 5 Hz when the segment number increases from 0 to 2. Over 40 light-emitting diodes can be lit by the harvester with a rectifying circuit. This work affords an opportunity for designing more efficient triboelectric energy harvesters with a broad bandwidth.