The majority of MEMS vibration sensors requires relatively high resonance frequencies of several kilohertz to avoid mechanical contact of moving parts such as electrode plates. In contrast to that, our hybrid micro-opto-electromechanical system (MOEMS) enables sensor applications at low frequencies. This work describes a distinct MOEMS featuring extremely low resonance frequencies of below 200 Hz. It is operated ambient air without closed loop feedback, extensive electronics and cooling. Due to the soft suspension of the micro-mechanical sub-system the fundamental limit, the Brownian noise floor, is reached. The resulting noise equivalent displacement for frequencies above the resonance is 1.9 pm/√Hz, which is equivalent to 0.29 μg/√Hz below the resonance. We describe the design space for sensors with further enhanced sensitivity and resonance frequencies far below 100 Hz.
Hortschitz, W., Kainz, A., Steiner, H., Stifter, M., Kohl, F., Schalko, J., … Keplinger, F. (2014). MOEMS vibration sensor for advanced low-frequency applications with pm resolution. In Procedia Engineering (Vol. 87, pp. 835–838). Elsevier Ltd. https://doi.org/10.1016/j.proeng.2014.11.282