Mode-localized accelerometer with ultrahigh sensitivity

The mode localization phenomenon is an effective technique to enhance sensor sensitivity, and some low noise floor mode-localized sensors, including accelerometers, mass sensors, and electrometers, have been successfully realized. To further improve the performance of the mode-localized accelerometer, we report a microelectromechanical system mode-localized accelerometer based on 4-degree of freedom (DoF) weakly coupled resonators (WCRs) with a stress-relief structure eliminating the thermal stress generated during the silicon-on-glass fabrication process. Experimental results show that compared with the state-of-the-art 3-DoF mode-localized accelerometer (4.40 g⁻¹), the amplitude ratio-based sensitivity of the proposed accelerometer (119.36 V·g⁻¹) is improved by 2612%. Moreover, the noise floor is 0.64 µg·Hz^−1/2 from 0.01 to 3 Hz under the closed-loop circumstance. To the authors’ best knowledge, this is the lowest measured noise floor for mode-localized accelerometers.