Micromechanical resonant electrostatic charge sensor with micro-leverage mechanisms

A micromachined resonant electrostatic charge sensor with enhanced responsivity by introducing dual single-stage micro-leverage mechanisms is presented. The sensor is based on the detection of resonant frequency shift of a single-crystal silicon double-ended tuning fork (DETF) element due to the axial compressive generated by the additional charge and transformed by the micro-levers. An analytic model was derived in detail comprising both mechanical and electrical subsystems. The quality factor of the resonator is about 4,900 at an operating pressure of 40 mTorr, with a nominal resonant frequency of 139 kHz. The amplification factor of the double micro-levers excides 8. In addition, we experimentally demonstrated that the responsivity enhanced and the sensitivity is 21 fC under 4 ppm frequency fluctuation.