A Vibration Energy Harvester With Targeted Frequency-Tuning Capability

One of the major challenges for vibration energy harvesters is to match their resonant frequency with ambient vibration frequency. The main limitation of the existing frequency-tuning techniques is the uncontrollable tuning process, i.e., the incapability of tuning the frequency to a desired value. In this article, we report a tunable electromagnetic vibration energy harvester capable of being tuned to a specific target frequency. The device adjusts the resonant frequency by changing the effective length of two polyimide springs through a set of smart tuning structures with scales. A maximum frequency tuning range of 58 Hz (46 Hz-104 Hz, 126% relative tuning range) is realized with the proposed device. At a sinusoidal acceleration of 1g, an output peak-to-peak voltage of 263.4 mV and an output power of 143.6 μW are obtained at the frequency of 56 Hz.