An Energy Harvester concept for electrostatic conversion manufactured in MEMS surface micromachining technology

In this work we present the concept of a MEMS-based Energy Harvester (EH) for the conversion of vibration into electrical energy. The employed electrostatic conversion mechanism of the device is sensitive both to vertical (out-of-plane) and horizontal (in-plane) displacements, thanks to the presence of buried planar and interdigitated fixed electrodes, respectively. The proposed EH is inexpensively manufactured in the MEMS/RF-MEMS surface micromachining process available at Fondazione Bruno Kessler (FBK) in Italy, and, thereby, does not require any specific technology modification to be realized. Modeling of the EH concept (Finite Element Method based and analytical) is reported and discussed, and validated against preliminary experimental measurements. The structure exhibits resonant frequencies in the range up to 10-12 kHz, it being compatible with vibration sources typically available in the surrounding environment, like busy street, car engine, industrial and domestic appliance, and so on. Preliminary estimates of the power conversion capability seem to address rather low levels (in the range of pW), despite, on the other hand, the EH design as well as the fabrication process admit significant margins of performance improvement.