Development of wide frequency range-operated micromachined piezoelectric generators based on figure-of-merit analysis

This paper presents a novel micromachined piezoelectric generator harvesting mechanical energy over a wide frequency range. According to systematic figure of merit (FOM) analysis, four optimized design devices of cantilevers with proof-masses are selected to be connected in parallel to form a generator of size 3 x 3 x 5 mm. Moreover, the devices are fabricated by an innovative process where the piezoelectric active areas on the cantilever are supported by flexible membranes to achieve a large displacement with minimum residual stress. When the generator is operated in a vibration environment, the deposited piezoelectric films on the cantilever structures induce charge for power generation. According to experimental characterization of the sputtered ZnO film, the developed generator produces from tens of picowatts to hundreds of nanowatts of power over a reasonably wide frequency range.