Enhanced Mode Localization in 2-DoF Weakly Coupled Electrostatic MEMS Resonant Sensor Devices via Blue-Sideband Excitation

This article for the first time introduces the blue-sideband excitation (BSE) scheme to two types of 2-degree-of-freedom (2-DoF) weakly coupled electrostatic resonant sensors, i.e., a 2-DoF electrostatically coupled resonating system with parallel suspension beams (Device 1) and a 2-DoF coupled double-ended tuning fork (DETF) resonant device (Device 2), boosting the functionality of the mode localization phenomena and ultimately achieving distinct performance upgradation. The amplitude ratio (AR) is hence adopted as the readout metric for the sensitivity characterization with respect to different external stiffness perturbations introduced by the capacitive transduction. Three paradigms of AR were implemented in this subject, namely, intermodal AR (IM-AR), interresonator AR (IR-AR), and interresonator-IM-AR (IRIM-AR), owing to the feature of simultaneous multiple-mode excitation of BSE. A comparison regarding the coupled resonant devices subject to the conventional drive scheme and the BSE was conducted, where the experimental results indicated that more than two orders of magnitude enhancement in sensitivity were achieved with the BSE scheme, along with the possibility of a pronounced ~17 times improvement in the noise floor, as well as the capability of simultaneous multiple parameter extraction across different resonators and vibration modes within the coupled system. This work further verified the feasibility and effectiveness of the BSE scheme, demonstrating the potential of such a technique for sensing applications based on mode-localized resonant sensors, fostering ultrahigh performance augmentation.