Enhancing Parametric Sensitivity in Electrically Coupled MEMS Resonators

• Published in: Journal of microelectromechanical systems Vol. 18; no. 5; pp. 1077 - 1086
• Main Authors: Thiruvenkatanathan, P., Jize Yan, Woodhouse, J., Seshia, A.A.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.10.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Arrays; Councils; Couplings; Electrical coupling; Electrostatics; Exact sciences and technology; Fabrication; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Localization; Mechanical instruments, equipment and techniques; Mechanical sensors; Microelectromechanical systems; Micromechanical devices; Micromechanical devices and systems; mode localization; parametric sensitivity; Perturbation; Physics; Position (location); Resonance; Resonant frequency; Resonators; Springs; Stiffness; Studies; Vibration measurement; Vibration mode; Mode coupling; Coupled oscillator; Measurement sensor; parametric sensitivity; Frequency shift; Restoration; High sensitivity; mode localization; Resonance frequency; Electrical coupling; Vibrational modes; Resonators; Microelectromechanical device; Localized modes
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2009.2025999

In an array of identical resonators coupled through weak springs, a small perturbation in the structural properties of one of the resonators strongly impacts coupled oscillations causing the vibration modes to localize. Theoretical studies show that measuring the variation in eigenstates due to such vibration-mode localization can yield orders of magnitude enhancement in signal sensitivity over the technique of simply measuring induced resonant-frequency shifts. In this paper, we propose the application of mode localization for detecting small perturbations in stiffness in pairs of nearly identical weakly coupled microelectromechanical-system resonators and also examine the effect of initial mechanical asymmetry caused by fabrication tolerances in such sensors. For the first time, the variation in eigenstates is studied by coupling the resonators using electrostatic means that allow for significantly weaker coupling-spring constants and the possibility for stronger localization of vibration modes. Eigenstate variations that are nearly three orders of magnitude greater than the corresponding shifts in the resonant frequency for an induced perturbation in stiffness are experimentally demonstrated. Such high electrically tunable parametric sensitivities, together with the added advantage of intrinsic common-mode rejection, pave the way to a new paradigm of mechanical sensing.