Piezoelectric MEMS Energy Harvester by Using Collision Impact of Droplets

This research includes investigation, prototyping, and evaluation of MEMS piezoelectric vibration energy harvesters from falling droplets. The devices have a simple structure, consisting of a 10×5×0.02 mm3 Si cantilever with 10 µm thick PZT thin films. The cantilever was coated with hydrophobic resin for electrical insulation and high Q factor. The collision impact of the droplets vibrates the cantilever and PZT generates the electric power. In this paper, two types of the device, with and without a proof mass at the free end of the cantilever, were fabricated and evaluated. The experiments showed that the device with mass generates maximum voltage of 5.7 V and the total energy of 313 nJ from one droplet of 15 µJ.