State-of-the-Art in Mode-Localized MEMS Coupled Resonant Sensors: A Comprehensive Review.

This article reviews the investigation of the mode-localized microelectromechanical system (MEMS) coupled resonant sensors. This class of a sensor features a new approach in the sensing method (i.e. sensing shifts in the eigenstates/amplitude ratio (AR) instead of a frequency shift) in resonant devices. The key performance metrics and progress in terms of sensitivity, noise optimization, resolution, output stability, and bandwidth are closely observed for the resonant devices that use multi-degree of freedom (m-DoF) resonators for transduction and subsequent sensing. A critical analysis, insight, and wide-ranging applications are studied for the mode-localized sensors that operate in a vacuum (with a higher quality factor, ${Q}$) or in an atmospheric pressure environment. Parameters such as the role of the operating/bias point, modal overlap, different forms of the output, and nonlinearity in the output are analyzed. The impact of structural asymmetry and how it can contribute to the performance enhancement of the sensor design is reported. An operation of the mode-localized sensors in the open/closed-loop configuration, in linear and nonlinear regions, is presented to understand the attempts made to enhance/optimize the sensor performance. Several potential applications developed particularly in the past five-year time span are discussed. Future endeavors and concluding remarks are offered for this emerging class of a coupled resonant (CR) sensor that features unprecedented ultrahigh parametric sensitivity, parallel detection capability of multiple analyte/s, and inherent common-mode rejection. [ABSTRACT FROM AUTHOR]