Several free-free beam micro-resonators are designed and fabricated using two commercially available surface micromachining processes, the UW-MEMS process and PolyMUMPs. Theoretical derivations of the design parameters are presented and an electrical lumped behavior model is developed for a single resonator with direct mechanic-to-electric analogy. A finite-element analysis (FEA) tool, the COMSOL Multiphysics 4.2a, is utilized to simulate the effects of the critical structural dimensions and electromechanical coupling. A variety of analyses, such as modal, static and dynamic responses are performed in FEA and the results are compared with the analytical solutions. The static and dynamic performances of the fabricated UW-MEMS resonators are tested using the Vecco NT-9100 In-Motion System. The electrical testing is carried out to obtain the frequency characteristics in electrical domain of the device. Measured data are compared with the analytical and simulation results. Discrepancies are discussed and analyzed.

No description available.

This thesis presents the design and development of a novel two-axis micromirror utilizing electrostatic, repulsive-force rotational actuators for laser scanned vector display systems. The micromirror consists of a 1.0 mm reflective mirror plate that can be rotated at high speeds to steer a laser beam to generate images. Fabricated using PolyMUMPs, the micromirror is operated in a non-resonant mode between 0 V and 200 V and can achieve a maximum optical scanning angle of ±2.6° in each axis with a settling time as fast as 2.75 ms and a first resonant frequency of 1400 Hz. Open-loop control methods were developed for image correcting and improving image quality. The micromirror was integrated into a portable, handheld vector display device which included designing and developing driving circuits, device firmware, mechanical components and optical components.

This thesis presents the design and development of a novel two-axis micromirror utilizing electrostatic, repulsive-force rotational actuators for laser scanned vector display systems. The micromirror consists of a 1.0 mm reflective mirror plate that can be rotated at high speeds to steer a laser beam to generate images. Fabricated using PolyMUMPs, the micromirror is operated in a non-resonant mode between 0 V and 200 V and can achieve a maximum optical scanning angle of ±2.6° in each axis with a settling time as fast as 2.75 ms and a first resonant frequency of 1400 Hz. Open-loop control methods were developed for image correcting and improving image quality. The micromirror was integrated into a portable, handheld vector display device which included designing and developing driving circuits, device firmware, mechanical components and optical components.

This thesis focuses on pioneering a scalable route to fabricate quantum information devices based upon single InAs/InP quantum dots emitting in the telecommunications wavelength band around 1550 nm. Using metallic gates in combination with nanotemplate, site-selective epitaxy techniques, arrays of single quantum dots are produced and electrostatically tuned with a high degree of control over the electrical and optical properties of each individual quantum dot. Using metallic gates to apply local electric fields, the number of electrons within each quantum dot can be tuned and the nature of the optical recombination process controlled. Four electrostatic gates mounted along the sides of a square-based, pyramidal nanotemplate in combination with a flat metallic gate on the back of the InP substrate allow the application of electric fields in any direction across a single quantum dot. Using lateral fields provided by the metallic gates on the sidewalls of the pyramid and a vertical electric field able to control the charge state of the quantum dot, the exchange splitting of the exciton, trion and biexciton are measured as a function of gate voltage. A quadrupole electric field configuration is predicted to symmetrize the product of electron and hole wavefunctions within the dot, producing two degenerate exciton states from the two possible optical decay pathways of the biexciton. Building upon these capabilities, the anisotropic exchange splitting between the exciton states within the biexciton cascade is shown to be reversibly tuned through zero for the first time. We show direct control over the electron and hole wavefunction symmetry, thus enabling the entanglement of emitted photon pairs in asymmetric quantum dots. Optical spectroscopy of single InAs/InP quantum dots atop pyramidal nanotemplates in magnetic fields up to 28T is used to examine the dispersion of the s, p and d shell states. The g-factor and diamagnetic shift of the exciton and charged exciton states from over thirty single quantum dots are calculated from the spectra. The g-factor shows a generally linear dependence on dot emission energy, in agreement with previous work on this subject. A positive linear correlation between diamagnetic coefficient and g-factor is observed.

Biological membranes are quasi two-dimensional self-assembled structure, primarily serving as a barrier to the leakage of cell’s contents. The main constituents of biological membrane are various amphiphilic lipids that form bilayers in an aqueous environment. These lipids carry acidic and/or basic functional groups that ionize in water, giving some of them a net electrical charge. Such a lipid molecule, when integrated into the membrane, experiences electrostatic forces from all other charged objects around it, including ions, surrounding lipids, and other molecules such as cationic peptides. The electrostatic interaction can profoundly influence the membrane, to which many phenomena with physiological significance as well as biophysical interest can be ascribed. In this thesis, we concentrate on investigating the electrostatic properties of lipid membranes. First, we study how the electrostatic interaction affects their preferred structure. To this end, we adopt a coarse-grain model that preserves the dominant characteristics of the lipids, in which the electrostatic interaction is treated within the “renormalized” Debye-H¨uckel theory. In particular, we calculate the spontaneous curvature of a phospholipid monolayer, along with other associated quantities. Our results suggest that such divalent ions as Mg2+ can stabilize HII phases of lipids (inverted hexagonal phases), which would otherwise form lamellar phases. Second,we investigate the competitive binding of ions and cationic peptides onto a monolayer of lipopolysaccharide (LPS) molecules, a class of highly charged bio-molecules found in the outer leaflet of the outer membranes of gram-negative (G-) bacteria. Cationic anti-microbial peptides (AMPs) can selectively kill bacteria, and it is suggested that they destabilize the LPS layer, easing their permeation across it, a process of great physiological and clinical interest. To this end, we model the LPS layer as a collection of charged “binding sites”, based on which we study the binding of cations (monovalent and divalent) and cationic peptides onto the layer. Our calculations suggest that the peptides can compete with divalent ions on the binding to the layer. It has been empirically known that since the stability of an LPS layer relies greatly on the bridging of divalent ions, the substitution of these ions by the peptides significantly compromises its stability. Our results offer a quantitative basis for this observation, thus providing a possible mechanism of an important step in the action of AMPs against G- bacteria.

Thesis (Ph. D.)--University of New South Wales, 2000. / Also available (in part) online.

Thesis (M.S.)--Ohio University, June, 2003. / Title from PDF t.p. Includes bibliographical references (leaves 71-72).

Thesis (M.S.)--Rochester Institute of Technology, 1989. / Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 21, 2009) Includes bibliographical references.