This thesis outlines the fabrication of two atom chips for the study of interactions between ⁸⁷Rb Rydberg atoms and a Au surface. Atom chips yield tightly confined, cold samples of an atomic species by generating magnetic fields with high gradients using microfabricated current-carrying wires. These ground state atoms may in turn be excited to Rydberg states. The trapping wires of Chip 1 are fabricated using thermally evaporated Cr/Au and patterned using lift-off photolithography. Chip 2 uses a Ti/Pd/Au tri-layer, instead of Cr/Au, to minimize interdiffusion. The chip has a thermally evaporated Au surface layer for Rydberg atom-surface interactions, which is separated from the underlying trapping wires by a planarizing polyimide dielectric. The polyimide was patterned using reactive ion etching. Special attention was paid to the edge roughness and electrical properties of the trapping wires, the planarization of the polyimide, and the grain structure of the Au surface.

This thesis outlines the fabrication of two atom chips for the study of interactions between ⁸⁷Rb Rydberg atoms and a Au surface. Atom chips yield tightly confined, cold samples of an atomic species by generating magnetic fields with high gradients using microfabricated current-carrying wires. These ground state atoms may in turn be excited to Rydberg states. The trapping wires of Chip 1 are fabricated using thermally evaporated Cr/Au and patterned using lift-off photolithography. Chip 2 uses a Ti/Pd/Au tri-layer, instead of Cr/Au, to minimize interdiffusion. The chip has a thermally evaporated Au surface layer for Rydberg atom-surface interactions, which is separated from the underlying trapping wires by a planarizing polyimide dielectric. The polyimide was patterned using reactive ion etching. Special attention was paid to the edge roughness and electrical properties of the trapping wires, the planarization of the polyimide, and the grain structure of the Au surface.

Reproduction : Thèse de doctorat : Archéologie : Lyon 2 : 2002. / Titre provenant de l'écran-titre. Bibliogr.

Reproduction de : Thèse de doctorat : Histoire contemporaine : Lyon 2 : 2003. / Titre provenant de l'écran-titre. Bibliogr.

Hardware Trojan Horses (HTHs or Trojans) are malicious design modifications intended to cause the design to function incorrectly. Globalization of the IC development industry has created new opportunities for rogue agents to compromise a design in such a way. Offshore foundries cannot always be trusted, and the use of trusted foundries is not always practical or economical. There is a pressing need for a method to reliably detect these Trojans, to prevent compromised designs from being put into production. This thesis proposes a multi-parameter analysis method that is capable of reliably detecting function-altering and performance-degrading Trojans in FPGA bitstreams. It is largely autonomous, able to perform functional verification and power analysis of a design with minimal user interaction. On-the-fly test vector generation and verification reduces the overhead of test creation by removing the need to pre-generate and verify test vector sets. We implemented the method on a testbed constructed from COTS components, and tested it using a red-team/blue-team approach. The system was effective at detecting performance-degrading and function-altering embedded within combinational or sequential designs. The method was submitted for consideration in the 2012 Embedded Systems Challenge, which served to independently verify our results and evaluate the method; it was awarded first place in the competition.

Development of wavelength selective detection, tunable multi-spectral capability with functionality in the infrared spectral region is highly desirable for a variety of applications such as thermography, chemical processing and environmental monitoring, spectroradiometry, medical diagnosis, Fourier transform infrared spectroscopy, night vision, mine detection, military defense and astronomy. Infrared detector with wavelength selective functionality have emerged as next generation infrared detectors. This study presents fabrication and characterization of wavelength selective Germanium dielectric coated Salisbury screen and novel 3D stacked microbolometer for multispectral infrared detection. This novel fabrication process helps produce much flatter, more robust device structure by using an un-patterned sacrificial layer to produce device legs that hold the central structural layer above the reflective mirror supported by a completely flat sacrificial layer with sufficient thermal isolation to allow microbolometer operation. For the fabricated wavelength selective Germanium dielectric coated Salisbury screen microbolometer using self aligned process, the FTIR measured spectral responses and numerical simulation results show excellent agreement with wavelength selectivity (9[mu]m, 10[mu]m, 11[mu]m) in long wave infrared (LWIR) region. To achieve multicolor infrared detection, recently a few device concepts using uncooled detectors have been reported. However, none of the proposed device designs have demonstrated fabrication. Moreover, Commercial Fabry-perot resonant cavity based uncooled microbolometers (Air gap: 2 to 2.5μm) have limited design parameters due to multicolor narrow band spectral response. In this study, a feasible device fabrication method for novel 3D stacked microbolometer is demonstrated for multispectral uncooled infrared detector that can achieve tunable narrowband absorption in mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral regions. / text

It has only been within recent decades that the complexity and heterogeneity of the biofilm mode of bacterial existence has been widely appreciated. Biofilms have persisted for billions of years as social communities of cells aggregated and attached on surfaces, and today they are both necessary and harmful within the human body and our surrounding environment. They show extremely high antibiotic resistance relative to planktonic cells and are sources of persistent infections. Biofilms are also the most common cause of failure for indwelling biomedical devices and implants. As a result, research efforts and commercial developments are focusing on creating better biomaterials that prevent bacterial attachment to surfaces leading to biofilm formation. While chemical methods to combat bacterial infections have been around for over a century in the form of antimicrobials, relatively little is known about how topographical methods can prevent bacterial attachment to surfaces. The reason for this is that micro- and nano-scale fabrication technologies (which are needed to produce topographies on size scales that might be expected to influence bacterial attachment) are fairly recent developments. In this thesis work, microscale topographies were developed for probing and influencing bacterial attachment to surfaces using dynamic-mask multiphoton lithography. Multiphoton lithography is an inherently three-dimensional fabrication technique. When combined with the dynamic-mask-based technology developed in the Shear laboratory, it allows for rapid prototyping of 3D structures of arbitrary complexity with submicron resolution in the radial dimension. A variety of topographical approaches for influencing bacterial attachment of Pseudomonas aeruginosa cells were explored within this work. P. aeruginosa was selected as a model organism for biofilm formation and because it is commonly isolated from infections associated with biomedical implant devices. Topographical approaches included the design of topographies based on microscale surfaces of naturally-antifouling leaves and mathematical functions, pillars, and surfaces containing various sizes and geometries of holes. Challenges relating to an imaging artifact caused by light scattering induced by the surfaces shed light on issues associated with assessing bacterial attachment levels on microscale topographical surfaces. Finally, future directions for this work are presented with ideas that extend into the nanoscale regime. / text

Directional microphones, which suppress noise coming from unwanted directions while preserving sound signals arriving from a desired direction, are essential to hearing aid technology. The device presented in this paper abandons the principles of standard pressure sensor microphones, dual port microphones, and multi-chip array systems and instead employs a new method of operation. The proposed device uses a lightweight silicon micromachined structure that becomes “entrained” in the oscillatory motion of air vibrations, and thus maintains the vector component of the air velocity. The mechanical structures are made as compliant as possible so that the motion of the diaphragm directly replicates the motion of the sound wave as it travels through air. The microphone discussed in this paper achieves the bi-directionality seen in a ribbon microphone but is built using standard semiconductor fabrication techniques and utilizes piezoelectric readout of a circular diaphragm suspended on compliant silicon springs. Finite element analysis and lumped element modeling have been performed to aid in structural design and device verification. The proposed microphone was successfully fabricated in a cleanroom facility at The University of Texas at Austin. Testing procedures verified that the resonant frequency of the microphone, as expected, was much lower than in traditional microphones. This report discusses the theory, modeling, fabrication and testing of the microphone. / text

One of the challenges in tissue engineering is to fabricate scaffolds which can mimic the natural microenvironments of cells. In a cell niche, biophysical and mechanical cues are crucial factors influencing cell functions. Given the complexity of natural extracellular matrix (ECM) engineered ECMs providing controllable biophysical and mechanical cues are appealing both in enhancing the understanding of cell-matrix interaction and in controlling cell fates in vitro. The ultimate goal of our study is to establish a platform as an engineered ECM by fabricating customized solid protein microstructures from solution using two-photon photochemical crosslinking, a novel laser-based freeform fabrication technique. In this study, protein structures varying from submicron lines, 2D micropatterns and microporous matrices, to 3D micropillars were successfully fabricated, demonstrating freeform fabrication capability with two-photon photochemical crosslinking. Two-photon fluorescent imaging and scanning electron microscope (SEM)-based microstructural characterization revealed that power, scan speed, total exposure time and concentrations of protein (bovine serum albumin) and photosensitizer (rose Bengal) in the solution were crucial processing parameters in this fabrication technique. Quantitative imaging analysis showed that porosity of protein matrices was highly dependent on processing parameters including power, scan speed, number of cycles in time series scan and protein concentrations in the solution. An atomic force microscopy (AFM)-based step change nano-compression test was used to measure the reduced elastic modulus of 3D viscoelastic protein micro-pillars fabricated, as a pilot study. Microporous protein matrices and 3D micropillar arrays fabricated with two-photon photochemical crosslinking can be used as engineered ECM for future study in cell-ECM interactions. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

abstract / Mechanical Engineering / Doctoral / Doctor of Philosophy