We use normal mode decomposition to obtain phonon properties from quasi-harmonic lattice dynamics calculations and classical molecular dynamics simulations in unstrained Lennard-Jones argon superlattices with perfect and mixed interfaces. Debye scaling of phonon lifetimes at low frequencies in both perfect and mixed superlattices and Rayleigh scaling for intermediate frequencies in mixed superlattices is observed. For short period mixed superlattices, lifetimes below the Ioffe-Regel limit are observed. The relaxation-time approximation of the Boltzmann transport equation is used to predict cross-plane and in-plane thermal conductivity. We find that using a dispersion relation which includes the secondary periodicity is required to predict thermal conductivity. The assumption of perturbative disorder, where Tamura elastic mass defect scattering theory can be applied, was found to be valid for predicting cross-plane thermal conductivities but not in-plane thermal conductivities in mixed superlattices.

Parallel Kinematic Mechanisms (PKMs) are well suited for high-accuracy applications such as meso-milling. However, drawbacks such as limited platform tilting angle and high configuration dependency of stiffness often limit their usage. In this Thesis, a new six degree-of-freedom (dof) PKM architecture based on a 3×PPRS topology is proposed, in order to address these problems. The new PKM is presented, and its inverse kinematics and Jocobian matrix are derived. The kinematic relations are incorporated into MATLAB to calculate the workspace of the PKM. The stiffness of the new PKM is obtained using Finite Element Analysis (FEA), and configuration dependency of stiffness is investigated. The proposed new mechanism is compared with three similar existing 6-dof PKMs, and it is shown that the new PKM exhibits higher stiffness. Lastly, three meso-Milling Machine Tool prototypes were designed and built. In particular, Prototype III is based on the new mechanism.

Several research groups have applied elevated hydrostatic pressure to ONH astrocytes cultured on a rigid substrate as an in vitro model for glaucoma. These studies have shown significant biological effects and this hydrostatic pressure model is now becoming generally accepted in the ophthalmic community. However, since the applied pressures were modest the finding of significant biological effects due to pressure alone is surprising. We hypothesized that the application of hydrostatic pressure as described in these studies also altered gas tensions in the culture media. Our goal was to design equipment and carry out experiments to separate the biologic effects of pressure from those of hypoxia on cultured astrocytes. We designed equipment and carried out experiments to subject cultures of DITNC1 astrocytes to the four combinations of two levels of each parameter. We explored the morphology and migration rates of astrocytes, but observed no significant change in any of these properties.

The effect of particle size, velocity, and angle of attack was investigated on the roughness and erosion rate of unmasked channels machined in borosilicate glass using abrasive jet micro-machining (AJM). Single impact experiments were conducted to quantify the damage due to the individual alumina particles. Based on these observations, an analytical model from the literature was modified and used to predict the roughness and erosion rate. A numerical model was then developed to simulate the brittle erosion process leading to the creation of unmasked channels as a function of particle size, velocity, dose, impact angle and target material properties. For the first time, erosion was simulated using models of two damage mechanisms: crater removal due to the formation and growth of lateral cracks, and edge chipping. Accuracy was further enhanced by simulating the actual relationship between particle size, velocity and radial location within the jet using distributions measured with high-speed laser shadowgraphy. The process of post-blasting AJM channels with abrasive particles at a relatively low kinetic energy was also investigated in the present work by measuring the roughness reduction of a reference unmasked channel in borosilicate glass as a function of post-blasting particle size, velocity, dose, and impact angle. The numerical model was modified and used to simulate the post-blasting process leading to the creation of smooth channels as a function of particle size, velocity, dose, impact angle, and target material properties. Finally, the effect of alumina particle kinetic energy and jet impact angle on the roughness and erosion rate of channels machined in borosilicate glass using abrasive slurry jet micro-machining (ASJM) was investigated. The analytical and numerical models derived for AJM, were found to predict reasonably well the roughness and the erosion rate of ASJM channels, despite the large differences in the fluid media, flow patterns, and particle trajectories in AJM and ASJM.

The effect of particle size, velocity, and angle of attack was investigated on the roughness and erosion rate of unmasked channels machined in borosilicate glass using abrasive jet micro-machining (AJM). Single impact experiments were conducted to quantify the damage due to the individual alumina particles. Based on these observations, an analytical model from the literature was modified and used to predict the roughness and erosion rate. A numerical model was then developed to simulate the brittle erosion process leading to the creation of unmasked channels as a function of particle size, velocity, dose, impact angle and target material properties. For the first time, erosion was simulated using models of two damage mechanisms: crater removal due to the formation and growth of lateral cracks, and edge chipping. Accuracy was further enhanced by simulating the actual relationship between particle size, velocity and radial location within the jet using distributions measured with high-speed laser shadowgraphy. The process of post-blasting AJM channels with abrasive particles at a relatively low kinetic energy was also investigated in the present work by measuring the roughness reduction of a reference unmasked channel in borosilicate glass as a function of post-blasting particle size, velocity, dose, and impact angle. The numerical model was modified and used to simulate the post-blasting process leading to the creation of smooth channels as a function of particle size, velocity, dose, impact angle, and target material properties. Finally, the effect of alumina particle kinetic energy and jet impact angle on the roughness and erosion rate of channels machined in borosilicate glass using abrasive slurry jet micro-machining (ASJM) was investigated. The analytical and numerical models derived for AJM, were found to predict reasonably well the roughness and the erosion rate of ASJM channels, despite the large differences in the fluid media, flow patterns, and particle trajectories in AJM and ASJM.

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 describes the development of a MEMS repulsive actuator capable of producing a large out-of-plane force. Existing MEMS repulsive actuators are low out-of-plane force actuators that are unable to support or lift a mass of 1 mg. A high force MEMS repulsive actuator was developed to overcome this limitation. The design was optimized employing parameters of the actuator’s fingers to increase the out-of-plane force. A design was developed based on the analytical results derived from extending the mathematical model of an existing actuator. A commercial manufacturing process, PolyMUMPs, was used to fabricate a prototype which was tested to validate the analytical and computational results. The prototype achieved an out-of-plane displacement of 15 µm and a 0.2° angular rotation. The resonance frequency was 120 Hz, and the rise and fall times were measured as 14.5 ms and 3625 ms (3.6 sec), respectively. The estimated out-of-plane force is 40 µN.

Magnetic resonance imaging is often used as a source for reconstructing vascular anatomy for the purpose of computational fluid dynamics (CFD) analysis. We recently observed large discrepancies in such “image-based” CFD models of the normal common carotid artery (CCA) derived from contrast enhanced MR angiography (CEMRA). A novel quantitative comparison of velocity profile shape of N=20 cases revealed an average 25% overestimation of velocities by CFD, attributed to a corresponding underestimation of lumen area in the CEMRA-derived geometries. We hypothesized that this was due to blurring of edges in the images caused by dilution of contrast agent during the relatively long elliptic centric CEMRA acquisitions, and confirmed this with MRI simulations. CFD simulations incorporating realistic inlet velocity profiles and non-Newtonian rheology had a negligible effect on velocity profile skewing, suggesting a role for other sources of error or modeling assumptions.

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 describes the development of a MEMS repulsive actuator capable of producing a large out-of-plane force. Existing MEMS repulsive actuators are low out-of-plane force actuators that are unable to support or lift a mass of 1 mg. A high force MEMS repulsive actuator was developed to overcome this limitation. The design was optimized employing parameters of the actuator’s fingers to increase the out-of-plane force. A design was developed based on the analytical results derived from extending the mathematical model of an existing actuator. A commercial manufacturing process, PolyMUMPs, was used to fabricate a prototype which was tested to validate the analytical and computational results. The prototype achieved an out-of-plane displacement of 15 µm and a 0.2° angular rotation. The resonance frequency was 120 Hz, and the rise and fall times were measured as 14.5 ms and 3625 ms (3.6 sec), respectively. The estimated out-of-plane force is 40 µN.