Simulation, Fabrication and Characterization of Robust Vibrational Energy Harvester

A new concept for the realization of cheap and robust energy harvester which converts mechanical vibrational energy into useful electrical energy using flexible PDMS pillars and a SiO2-electret is presented. Soft PDMS pillars are used as springs connecting a fixed and a movable electrode. Structuring of PDMS is done by punching, thus avoiding any micro structuring technique whereas in an earlier work structuring of PDMS was done via photolithography and finally RIE etching of a hard mask. The fixed electrode is oxidized with thermal wet oxidation technique to form a 0.25 μm thick electret and the electret is charged up to -260 V. Pre-treatment by plasma activation was used to increase the bond strength of PDMS. A new concept for power switching has been developed using flyback converter and thus detecting the phases of harvesting and extracting energy at proper phase in the cycle created by arbitrary motion. By this concept we are able to harvest 0.23 nW power at 1 g vibration and 4.3MΩ load resistance. However, by scaling the size of the PDMS pillars from mm to μm using micromachining and by design changes which allow to harvest out of more than one direction of vibration, output power can be scaled from nW to mW.