MEMS electret energy harvester with embedded bistable electrostatic spring for broadband response

A MEMS electret vibration energy harvester with an embedded bistable electrostatic spring for broadband response is proposed. By using a vertical electret, the bistable potential can be realized without any complex structure or additional mechanism. Based on the 1D electrostatic model, a rigorous electromechanical model as well as an approximate model with reduced parameters are developed. Based on the normalized expression of the approximate model, which is identical to the velocity-damped resonant generator model, the performance of harvesters with the proposed mechanism has been characterized in detail for harmonic excitation, band-limited white noise, and colored noise. In addition, its performance has been compared with that of a conventional duffing-type bistable generator. It is confirmed that the present mechanism has advantages such as a lower frequency range, and outperforms the duffing counterpart for colored noise.