Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: Robert W. Birkmire, Dept. of Materials Science & Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (M.Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

With the given information that dendrimers have precisely controlled their sizes and spherical structures in the molecular level, the aim of this study is to show that dendrimer particles can become ordered into a self-assembled regular structure due to the nature of their regular sizes and shapes. For this project, melamine based generation 3 dendrimer was used for solution cast of thin films from the dendrimer-chloroform solutions with different casting conditions, i.e. various solution concentrations, casting temperatures, and substrates. As a result of these experiments, unique phenomena of highly ordered uniform 2-D contraction separations were observed during the solvent evaporation from the dendrimer films. The cast films from the concentration of 0.8 wt% and higher exhibit regular 2-D separation contraction patterns and make well-developed regularly arrayed structures due to the interaction between the contraction stresses and adhesion strength between films and substrates. From the DSC tests, both powder and cast film samples of a dendrimer show similar melting behaviors with different areas under the melting peaks. The results of these tests show that dendrimers, when they are in a descent environment that provides dendrimers with molecular mobility due to surface ionic bonding strength, can make a structural order and regularity in their macroscopic structures.

Graduation date: 1993

Artificial cardiovascular implants are now made mainly from extruded polytetrafluroethylene (PTFE). However, the limited haemocompatibility of PTFE causes blood clotting and results in early replacement. Many techniques are being developed to improve the haemocompatibility of such devices. One of the most promising techniques is to coat the devices with nitrogen-doped diamond-like carbon (NDLC) thin films. However, the structure of NDLC and its effect on the haemocompatibility of the coated devices have not been fully investigated as required for practical applications. In this thesis, ion beam deposited DLC and Nitrogen doped thin films on PTFE were investigated in order to have a better understanding of the relationships between the structure and biomedical properties of the DLC thin films.<p> DLC and NDLC thin films were synthesized using ion beam deposition. Commercially available PTFE sheets, which are similar to the material used for vascular grafts, were used as substrates for the DLC thin films. Silicon wafers were also utilized as substrates for condition optimization and property comparison. Raman spectroscopy, atomic force microscopy, X-ray photo emission spectroscopy and scanning electron microscopy were used to study the structural and morphological properties of the coated surface. The results show that the ion beam deposited thin films have a very smooth surface and exhibit low coefficient of friction and high adhesion to the substrate. Low concentration of nitrogen doping in DLC improved surface hardness and reduced surface roughness. Higher concentration of sp3 hybridized bonds was observed in the DLC thin films on Si than those on PTFE. DLC coating decreased the surface energy and improved the wettability of PTFE films.<p> The haemocompatibility of the pristine and DLC coated PTFE sheets were evaluated by platelet adhesion technique. The platelet adhesion results showed that the haemocompatibility of DLC coated PTFE, especially NDLC coated PTFE, was considerably improved as compared with uncoated PTFE. SEM observations showed that the platelet reaction on the coated PTFE was minimized as the platelets were much less aggregated and activated.

Graduation date: 1993

Artificial cardiovascular implants are now made mainly from extruded polytetrafluroethylene (PTFE). However, the limited haemocompatibility of PTFE causes blood clotting and results in early replacement. Many techniques are being developed to improve the haemocompatibility of such devices. One of the most promising techniques is to coat the devices with nitrogen-doped diamond-like carbon (NDLC) thin films. However, the structure of NDLC and its effect on the haemocompatibility of the coated devices have not been fully investigated as required for practical applications. In this thesis, ion beam deposited DLC and Nitrogen doped thin films on PTFE were investigated in order to have a better understanding of the relationships between the structure and biomedical properties of the DLC thin films.<p> DLC and NDLC thin films were synthesized using ion beam deposition. Commercially available PTFE sheets, which are similar to the material used for vascular grafts, were used as substrates for the DLC thin films. Silicon wafers were also utilized as substrates for condition optimization and property comparison. Raman spectroscopy, atomic force microscopy, X-ray photo emission spectroscopy and scanning electron microscopy were used to study the structural and morphological properties of the coated surface. The results show that the ion beam deposited thin films have a very smooth surface and exhibit low coefficient of friction and high adhesion to the substrate. Low concentration of nitrogen doping in DLC improved surface hardness and reduced surface roughness. Higher concentration of sp3 hybridized bonds was observed in the DLC thin films on Si than those on PTFE. DLC coating decreased the surface energy and improved the wettability of PTFE films.<p> The haemocompatibility of the pristine and DLC coated PTFE sheets were evaluated by platelet adhesion technique. The platelet adhesion results showed that the haemocompatibility of DLC coated PTFE, especially NDLC coated PTFE, was considerably improved as compared with uncoated PTFE. SEM observations showed that the platelet reaction on the coated PTFE was minimized as the platelets were much less aggregated and activated.

Mn12-acetate single-molecule magnets (SMMs) are nano-scale magnets showing a strong magnetic anisotropy, slow relaxation and stepwise magnetic hysteresis curves. Possible applications of Mn12-acetate, e.g. for ultra high density magnetic information storage device, quantum computation, and magnetic molecular electronics, have been suggested due to the unusual magnetic behavior. It is an important prerequisite for the applications to develop a reliable technique to organize the molecules on a surface and to detect the magnetic signals of the molecules. A solution evaporation technique combined with conventional lithography is a simple but reliable method to create Mn12-acetate thin film patterns on the micro/nano-scale. The method is demonstrated with a series of analysis. A superconducting quantum interference device (SQUID) shows a non-linear I-V (Current vs. Voltage) characteristic that is modulated by a magnetic flux inside the loop, allowing one to sense and analyze an extremely weak magnetic field. The miniaturized SQUID is appropriate for sensing the magnetic flux from the film structure of the molecular magnets. Theoretical ideas, fabrication, and a measurement technique of the device are presented. A new interesting system, the so-called superconductor/SMM hybrid, results from the experimental configuration. Understanding this new type of hybrid system is important not only because of the expectation of new phenomena affecting the functionality of superconducting devices, but also because the two coupled substances are fundamentally incompatible phases. The first experimental attempt to investigate the interaction between an aluminum superconducting film and Mn12-acetate SMMs will be discussed.

The usual way to remove the silicon layer is used by the solutions of HF and KOH to conduct the etching process, but those chemicals are dangerous for the humans. Therefore, this study proposes the method that uses the diamond millstone to reduce the thickness of the silicon wafer. It hopes that this method can effectively shorten the process time and reduce the amount of chemical pollution. Firstly, the effects of the working pressure, the rotating speed of the wafer, and the diamond millstone on the removing rate of silicon wafer are investigated. Then, the effect of the working pressure on the flatness of the wafer surface is investigated. Finally, the effect of the rotating speed ratio of the wafer to the diamond millstone on the track type of grinding surface is theoretically analyzed. According to the experimental results, the removing rate of silicon wafer is almost linearly proportional to the working pressure, the rotating speed of the wafer, and the diamond millstone. The lighter working pressure, the more flatness of the wafer is. According to the theoretical results, the rotating speed ratio of the wafer to the diamond millstone influences the track type of grinding surface. When this rotating speed ratio is an irrational number, the distribution of grinding track becomes finer.