Passive Frequency Tuning of Piezoelectric Energy Harvester using Embedded Masses

The inability to tune the frequency of MEMS vibration energy harvesting devices is considered to be a major challenge which is limiting the use of devices in real world applications. Previous attempts are either not compatible with microfabrication, have large footprints, or use complex tuning methods which require power. This paper reports on a novel passive method of tuning the frequency by embedding nanopowder masses into a stationary proof mass with an array of cavities. The experimental and computational validation of changing and tuning the frequency is demonstrated. The change in frequency is caused from varying the location of the nanopowder filler in the proof mass to alter the center of gravity. The goal of this study was to validate the concept using macroscale piezoelectric energy harvesting devices, and to determine key parameters that affect the resolution and range of the frequency tuning capabilities. The experimental results demonstrated that the range of the frequency for the piezoelectric cantilever is 20.3 Hz to 49.1 Hz for this particular commercial macro-scale energy harvesting cantilever. Computational simulations had similar results of 23.7 Hz to 49.4 Hz. The resolution of tuning was <0.1 Hz.