The sensitivity of the resonant sensors has been proven to be remarkably enhanced by using mode localization of the weakly coupled resonators as the sensing mechanism. This paper reports a mode-localized resonant accelerometer (ML-RXL) with a novel designed micro-lever mechanical coupler, which is connected with two identical resonators and interconnects the strain energy flow 'leaked' from the non-ideal anchors of the two resonators to enable weak mechanical coupling. The coupling stiffness between the resonators can be reduced by optimizing the anchor to make it more ideal to weaken the leakage energy or optimizing the critical dimension of the micro-lever to weaken the transmission of the leakage energy. A finite element method (FEM) simulation model is established and the simulation results demonstrate that the two methods can effectively weaken the coupling strength between the resonators and improve the sensitivity. The wafer-level vacuum-packaged ML-RXL prototype device is fabricated using the silicon-on-insulator process and is performed in both open-loop and closed-loop tests respectively. The open-loop experiment results demonstrate that the sensitivity of the prototype can be improved from 8.86AR/g to 46.28AR/g, which is consistent with the FEM simulation results. The closed-loop experimental results demonstrate that the sensitivity of the prototype is 46.10AR/g under the linear range of 0.22 g. Moreover, the noise floor decreases from 4.39μg/Hz to 1.71μg/Hz within 10 Hz bandwidth, and the bias-instability decreases from 4.27 μg to 1.6 μg. 

Utilizing mechanical micro-lever coupling structure to enhance sensitivity in mode-localized MEMS accelerometer

This paper reports a DC electric field sensor (EFS) based on the mode localization phenomenon. The EFS consists of 3-degrees-of-freedom weakly coupled resonators (WCRs) and two capacitor arrays that are electrostatically coupled with the WCRs. The capacitor arrays sense the electric field and produce a stiffness perturbation that causes an amplitude ratio change of the WCRs. The EFS is fabricated using a silicon-on-insulator process and evaluated in a vacuum chamber. The amplitude ratio of the resonators changes from 2.2 to 7.5 as the electric field strength ranges from 0 to 7 kV/m, with a sensitivity of 0.76 /(kV/m). The noise, resolution, and stability of the mode-localized EFS are 11.5 (V/m)/√Hz, 22.9 V/m, and 9.1 V/m, respectively, which are competitive compared with that of other high-performance micromachined EFS.

Jin Guo

Papers

A Mode-localized DC Electric Field Sensor