Browsing by Author "Hans D. Hallen, Committee Chair"

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Alignment of Silicon wafers for 3D Packaging
(2007-07-27) Walker, Ernest Marshall; Hans D. Hallen, Committee Chair; Michael Paesler, Committee Member; Laura I. Clarke, Committee Member
Wafer level self-alignment is investigated with a Self assembled monolayer (SAM) deposition, SAM termination modification, friction dry and capillary alignment forces. SAMs are deposited on oxide layer, and characterized by ellipsometry and contact angle. Vinyl-terminated SAMs are oxidized to carboxyl-termination, which changes the wetting characteristics. Measurements for characterizing the layers are presented. The relative surface energies can also be estimated. From these characteristics it will be shown how surface energy is modified for the purpose of generating surface energy gradients in use with a self-alignment process. Self-alignment is observed using capillary forces, and exhibits a reasonable capture range. The self-alignment masks are used to increase this force and will be discussed.
Application of Diffraction Enhanced Imaging to Bone
(2007-01-24) Connor, Dean Michael Jr.; Zhong Zhong, Committee Member; Etta Pisano, Committee Member; D. Rick Sumner, Committee Member; David S. Lalush, Committee Member; Hans D. Hallen, Committee Chair; Keith Weninger, Committee Member
Diffraction enhanced imaging (DEI) is a new x-ray-based medical imaging modality that is in its early stages of development and testing. In images generated using DEI, contrast is from absorption and refraction of x-rays and from ultra-small angle x-ray scattering (USAXS). Though accepted values for x-ray absorption in biological tissues have been established, only recently have investigators began probing for characteristic refraction and USAXS from biological tissues. For this work, a series of four experiments were performed at the National Synchrotron Light Source (Upton, NY, USA) beamline X15A to help characterize DEI of bone. In the first experiment, the USAXS profile was measured for pre- and post-fatigue loaded cortical bone. Though no clear pattern of change in the USAXS profile was found, the bone samples were shown to have a measurable USAXS signal and it was found that large refracting structures within bone (>100 microns) could be visualized. In the next two experiments, the contrast of DEI?s refraction and apparent absorption images was compared to the contrast in synchrotron radiation (SR) radiographs for planar imaging of gap regions in bone and for imaging of trabecular structure in tomography mode. DEI was shown to have significant contrast-to-noise ratio gains over SR radiographs in both experiments. The planar refraction and apparent absorption signals in the gap imaging experiment were shown to be consistent with their theoretically predicted values. DEI in tomography mode (DECT) was found to have significant resolution gains over comparably obtained SRCT images. In the final experiment, a computer model was developed to predict USAXS from cortical bone and the computer model results were compared to USAXS data obtained using DEI. The scattering widths, as predicted by the computer model, suggest that osteocyte lacunae cause the experimentally measured angular spreading of the x-ray beam. The findings of these experiments provide the impetus for further studies of bone with DEI emphasizing clinical applications.
Electric-Field Induced Movement of MicroDroplets, Models and Design.
(2003-06-23) McLawhorn, Robert Allen; Hans D. Hallen, Committee Chair; Michael A. Paesler, Committee Member; H. Troy Nagle, Committee Member
The objective of this research is to model and design a microfluidic system that uses electrostatic fields to induce movement of discrete droplets of solution. Of particular interest is movement of droplets of H₂O for use in biological testing with lab-on-a-chip and mTAS systems. Using computer modeling, the electric-fields for planar electrode configurations positioned on an insulating substrate are calculated for a hemispherical drop of H₂O on the substrate at various positions. From these electric-fields the force on the drop is calculated. These models show that electrostatic actuation of droplets of H₂O is possible. However, as the complexity of the model increases the properties of the system become less desirable and actuation may not be possible. Using microfabrication techniques, the modeled microfluidic systems have been built for testing using a Kapton substrate with copper electrodes. Hexadecenyltrichlorosilane (HTS), a self-assembled monolayer, and its oxidant have been studied and found capable of providing hydrophobic and hydrophilic surface coatings for the systems.
Novel Split-Tip Probe for Molecular Orientation and Nonlinear Optical Studies
(2008-08-10) Taylor, Michael Phillip; Hien T. Tran, Committee Member; David E. Aspnes, Committee Member; Laura I. Clarke, Committee Member; Hans D. Hallen, Committee Chair