A micromachined energy harvester from a keyboard using combined electromagnetic and piezoelectric conversion

This paper describes a novel micromachined energy harvester, which can harness energy from typing motions on a computer keyboard. It converts mechanical energy into electrical energy by utilizing piezoelectric and electromagnetic conversion simultaneously for reciprocating z-directional motions of each key. We have fabricated and tested a micro power harvester chip integrated into a computer keyboard. Experimental results show that the maximum harvested power is about 40.8 µW with a 3 MΩ load from piezoelectric conversion, and 1.15 µW with a 35 Ω load from electromagnetic conversion. The micro power harvesters can be extended into the form of an array.