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 major parts: MEMS coupled structures and MEMS dynamic logic devices.
First, a theoretical and experimental investigation on both electrostatically and mechanically coupled resonator is presented. Static and dynamic analysis of weakly electrostatically coupled silicon microbeams, and strongly mechanically coupled polyimide microbeams is presented. 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 and dynamic response of the coupled system under different external perturbations is investigated. It is observed, that the exploitation of mode localization depends on the fact that which resonator of the coupled system is under direct excitation, which resonator’s stiffness is 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 capable of performing the AND/NAND logic gate and a tri-state logic gate using mixed-frequency excitation is presented that works 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 working on the principle of activation (1) and deactivation (0) of second resonant mode of a clamped-clamped microbeam is presented. This device is capable of performing OR, XOR and NOT gate. Experimental demonstration of the cascadability is shown for this case cascading and OR and NOT gate to perform a universal NOR logic gate.
Saad Ilyas received a B.S. degree in Mechanical Engineering from Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Pakistan in 2012. He is currently enrolled as a Ph.D. student in Mechanical Engineering in King Abdullah University of Science and Technology (KAUST). His research interests include linear and nonlinear dynamics of MEMS devices with applications in mechanical computing, sensors, and actuators. He is an author of 25 journal publications and 2 patents.