A MEMS magnetic-based vibrational energy harvester

Abstract

This thesis presents the design, fabrication, and testing of a MEMS vibration energy harvester that is to operate at low frequency to power machine health monitoring. The energy harvester converts external vibration into electricity via the Lorentz-force by allowing a permanent magnet, which acts as an inertial mass, to oscillate between coils wound above and below the magnet. Careful analysis and design of a fabricated silicon-based suspension, which holds the magnet, determines the important mechanical properties of the harvester, such as the internal loss and the selectivity of a single translational vibration. The harvester is designed to provide maximum power output at 0.5 g external acceleration at 50 Hz while its size is constrained to be less than 1 cm3. By incorporating mechanical and electromagnetic analyses, a full-system optimization is performed to determine the optimal dimensional parameters of the harvester and to estimate the power output to be observed. The fabricated and assembled energy harvester is tested and observed to produce an open-circuit voltage of 100 mV and a power output of 165 [mu]W at the resonance frequency of 45.7 Hz. The harvester's power density is 382 [mu]W/cm3, which is higher than the highest reported value of 222 [mu]W/cm3 for existing MEMS energy harvesters, but the performance of the design presented in this thesis may be improved with some changes to the current design.