Dynamics of electromagnetically-transduced microresonators
Abstract
Electromagnetic transduction is a means of actuating and sensing microelectromechanical systems (MEMS) through the interaction of electric and magnetic fields. Electromagnetically-transduced devices are Lorentz force actuated and sensed via an induced electromotive force (EMF). As such, transduction requires that the vibrations of one of these devices take place within a magnetic field. Provided one can leverage relatively recent advances with rare-earth magnets or complementary metal-oxide-semiconductor (CMOS) fabrication for magnetic field generation, electromagnetic transduction offers many distinct advantages over other methods of actuating and sensing MEMS. These advantages include the ability to generate large forces and moments that are linearly related to the supplied current, comparatively low power consumption metrics obtained with comparatively-low excitation voltages, and comparatively-simple device geometries that do not interfere with transduction. This type of transduction also facilitates operation in fluidic or harsh environments. In addition, an electromagnetically-transduced microresonator (ETM) could be used in the future for numerous applications which utilize a microresonator, such as electrical signal processing and resonant-based mass sensing, as well as self-sustaining oscillators. Other potential applications that are relatively unique to ETMs are a product of electromagnetic transduction, like magnetic field sensing. Arrays of electromagnetically-transduced devices could also be used to improve a sensor's throughput, or the total amount of sensed information, as it is comparatively-easy to electrically-couple multiple devices together. The efforts associated with the design, fabrication and characterization in both low-pressure and atmospheric conditions of one such array that has multiple, easily-tailored resonances with single-input, single-output (SISO) characteristics are documented in this dissertation. This type of electromagnetic coupling can also give rise to systems that are coupled via dissipative and global means. These globally-, dissipatively-coupled systems are capable of exhibiting collective phenomena like group attenuation, confined attenuation, and group resonance. In order to enable the previously-mentioned applications, an issue that is common to many MEMS must be addressed: input/output coupling, or parasitic feed\-through. Within this document, the influence of inductive and resistive coupling between the input and output of an ETM, in the presence of nonlinearity, is explored. It is shown, both theoretically and experimentally, that input/output coupling can cause significant qualitative differences between the mechanical and electrical responses of an ETM. Under conditions when the input/output coupling is insignificant, ETMs are a favorable platform for isolated and coupled oscillators due to their self-sensing nature. Besides having direct applications in timing and sensing, isolated and coupled ETM-based oscillators could be used as phase-shifterless beam-scanners, neurocomputers, or sensors with simplified detection requirements.
Degree
Ph.D.
Advisors
Rhoads, Purdue University.
Subject Area
Mechanical engineering|Electromagnetics|Theoretical physics
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