Fig. 1. Structure and working principle.

a Cross-sectional view of the energy harvester. b Schematic of the flexible-substrate stretching process that causes the cantilever release from the magnet and free resonance/generation at the up-conversion frequency. c Schematic of the flexible-substrate rebounding process that causes pull-in again of the cantilever end to generate electricity at the higher clamped-supported mode up-conversion frequency