A 2DOF MEMS Vibrational Energy Harvester

In this paper, a novel two-degree-of-freedom (2DOF) MEMS electromagnetic vibration energy harvesting system is proposed. The dual-mass resonant structure that comprises of a primary mass and an accessory mass is structured on silicon-on-insulator (SOI) wafer by double-sided deep reactive-ion etching (DRIE). Unlike previous 2DOF harvesters, the induction coil is only patterned on the primary mass for energy conversion. By carefully adjusting the weight of accessory mass, the first two resonances of the primary mass can be tuned close to each other while maintain comparable magnitudes. Therefore, both resonances could contribute to energy harvesting that make the system more efficient and adaptive in frequency-variant vibrational circumstances. With the current prototype, two close resonances with a frequency ratio of only 1.19 and comparable peaks are achieved, providing good validation for the modeling results.