Parametrically excited MEMS vibration energy harvesters

Resonant-based vibration harvesters have conventionally relied upon accessing the fundamental mode of resonance to maximise the conversion efficiency of mechanical-to-electrical power transduction. This paper explores the use of parametric resonance, which is not limited by linear damping and can potentially offer higher and broader nonlinear peaks. Despite the promising potential, a damping-dependent initiation threshold amplitude has to be overcome first. Design approaches have been explored to resolve this limitation. A numerical model has been constructed to analysis the improvements over the convention. An out-of-plane (to accommodate large displacements) electrostatic MEMS prototype (~ 0.147 mm3), driven at 4.2 ms-2, has demonstrated a peak power of 0.011 µW at the fundamental mode of resonance and 0.16 µW at the principal parametric resonance. A two fold increase in frequency bandwidth was also observed for the parametrically excited device.