Dynamics of MEMS Resonators and their Exploitation for Sensing and Actuation

  • Saad Ilyas

Student thesis: Doctoral Thesis

Abstract

This dissertation presents theoretical and experimental investigations into the dynamical behavior of Micro electromechanical systems (MEMS) resonators and their exploitation for filtering, sensing, and logic applications. The dissertation is divided into two parts: MEMS coupled structures and MEMS dynamic logic devices. First, a theoretical and experimental investigation is presented on both electrostatically and mechanically coupled resonator. Static and dynamic analysis is presented for weakly electrostatically coupled silicon microbeams and also for strongly mechanically coupled polyimide microbeams. The static analysis focuses on revealing pull-in characteristics, while the dynamic analysis focuses on the frequency response of the system and its exploitation for potential applications in filtering and amplification. Next, the phenomenon of mode localization is explored theoretically and experimentally on both electrostatically and mechanically weakly coupled resonators. Eigenvalue analysis is conducted and the dynamic response of the coupled system under different external perturbations is investigated. It is observed, that the exploitation of mode localization depends on the choice of the resonator to be under direct excitation, its stiffness to be perturbed, and which resonator is used to record the output results. These understandings will potentially help improve the performance of MEMS mode-localized sensors. Finally, three techniques to realize cascadable MEMS logic devices are presented. MEMS logic device vibrates at two steady states; a high on-resonance state (1) and a low off-resonance state (0). First, a MEMS logic device is presented capable of performing the AND/NAND logic gate and a tri-state logic gate using mixed-frequency excitation. This work is based on the concept of activation (1) and deactivation (0) of combination resonances due to the mixing of two or more input signals. Second, exploitation of subharmonic resonance under an AC only excitation to perform AND logic operation is presented. Finally, another MEMS logic device is presented working on the principal of activation (1) and deactivation (0) of second resonant mode of a clamped-clamped microbeam. This device is capable of performing OR, XOR and NOT gate. Experimental demonstration of the cascadability is shown for this case cascading OR and NOT gate to perform a logically complete NOR logic gate.
Date of AwardApr 2019
Original languageEnglish (US)
Awarding Institution
  • Physical Science and Engineering
SupervisorMohammad Younis (Supervisor)

Keywords

  • MEMS
  • Non linear Dynamics
  • Mechanical computing
  • Resonators
  • coupled resonators
  • theoretical modeling

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