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by Li Chong, Victor Kun Wa. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 99-101). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.iii / ACKNOWLEDGEMENT --- p.v / TABLE OF CONTENTS --- p.vii / LIST OF FIGURES --- p.x / LIST OF TABLES --- p.xv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- CD Manufacturing Technology --- p.1 / Chapter 1.1.1 --- Electroforming --- p.2 / Chapter 1.1.2 --- Computer Numerical Control (CNC) --- p.2 / Chapter 1.1.3 --- Photolithography --- p.4 / Chapter 1.1.4 --- Laser --- p.5 / Chapter 1.2 --- Research Objective --- p.6 / Chapter 1.3 --- Thesis Outline --- p.6 / Chapter 2 --- Conversion Software (AutoGEN) --- p.9 / Chapter 2.1 --- Computer-Aided Design --- p.9 / Chapter 2.2 --- AutoCAD Programming --- p.10 / Chapter 2.3 --- AutoCAD Development System (ADS) --- p.11 / Chapter 2.4 --- AutoCAD Runtime Extension (ARX) --- p.12 / Chapter 2.5 --- AutoLISP Programming --- p.12 / Chapter 2.5.1 --- Advantages of AutoLISP --- p.13 / Chapter 2.6 --- Caltech Intermediate Format (CIF) --- p.14 / Chapter 2.6.1 --- Structure of CIF Format --- p.15 / Chapter 2.7 --- Architecture of Conversion Software --- p.15 / Chapter 2.7.1 --- Stage 1 - AutoGEN (DLTM) Module --- p.16 / Chapter 2.7.2 --- Stage 2 - AutoGEN (DCRM) Module --- p.17 / Chapter 2.8 --- DLTM Input Screen --- p.17 / Chapter 2.9 --- DCRM Data Screen --- p.18 / Chapter 2.10 --- Conversion from 2D to 3D --- p.18 / Chapter 2.11 --- AutoGEN - Geometric Primitive --- p.19 / Chapter 2.12 --- AutoGEN - Geometric Transformation --- p.19 / Chapter 2.13 --- Conversion of Simplified and Complex Drawings --- p.22 / Chapter 3 --- Manufacturing Process --- p.24 / Chapter 3.1 --- Stamper Manufacturing --- p.25 / Chapter 3.2 --- CD Manufacturing --- p.30 / Chapter 3.3 --- Internal Stress of Deposit in Electroforming --- p.34 / Chapter 4 --- CNC Approach --- p.37 / Chapter 4.1 --- Computer-Aided Manufacturing --- p.37 / Chapter 4.2 --- CNC Machining --- p.37 / Chapter 4.2.1 --- Experiment --- p.39 / Chapter 4.3 --- Advantages of CNC Approach --- p.42 / Chapter 4.4 --- Limitations of CNC Approach --- p.42 / Chapter 4.5 --- CNC and Effects of Heat Generated --- p.43 / Chapter 5 --- Photolithography Approach --- p.45 / Chapter 5.1 --- Experiment --- p.47 / Chapter 5.2 --- Channel Analysis --- p.49 / Chapter 6 --- Laser Approach --- p.53 / Chapter 6.1 --- Dual Beam Laser Machine --- p.53 / Chapter 6.2 --- Creation of Pits and Lands --- p.54 / Chapter 6.2.1 --- Experiment --- p.54 / Chapter 6.3 --- Creation of Continuous Channel --- p.56 / Chapter 6.4 --- Procedure of Channel Creation (NA set at a fixed constant) --- p.57 / Chapter 6.4.1 --- Experiment 1 --- p.59 / Chapter 6.4.2 --- Experiment 2 --- p.60 / Chapter 6.4.3 --- Experiment 3 --- p.61 / Chapter 6.5 --- Procedure of Channel Creation (ILV set at a fixed constant) --- p.62 / Chapter 6.5.1 --- Experiment 1 --- p.63 / Chapter 6.5.2 --- Experiment 2 --- p.64 / Chapter 6.5.3 --- Experiment 3 --- p.66 / Chapter 7 --- Photolithography Approach (Enhancement) --- p.68 / Chapter 7.1 --- Creation of High-Aspect-Ratio Channel --- p.68 / Chapter 7.1.1 --- Experiment 1 --- p.76 / Chapter 7.1.2 --- Experiment 2 --- p.80 / Chapter 8 --- Conclusion and Future Proposal --- p.83 / Chapter 8.1 --- Conclusion --- p.83 / Chapter 8.2 --- Future Proposal --- p.86 / APPENDIX --- p.89 / Chapter A.1 --- Additional Information on CNC Approach --- p.88 / Chapter A.2 --- Channel Dimension of Design Mask --- p.89 / Chapter A.3 --- Additional Information on Photolithography Approach --- p.94 / Chapter A.4 --- Additional Information on Laser Approach --- p.95 / BIBLIOGRAPHY --- p.98

Micro-fluid mixing is an important aspect of many of the various micro-fluidic systems used in biochemical production, biomedical industries, micro-energy systems and some electronic devices. Typically, because of size constraints and laminar flow conditions, different fluids may only have the opportunity to mix by diffusion, which is extremely rate limited. Therefore, active or highly effective passive mixing techniques are often required. In this study, two pulsed injectors are used to actively enhance mixing in a high aspect ratio microchannel (125 ��m deep and 1 mm wide). The main channel has two adjacent flowing streams with 100% dye and 0% dye concentrations, respectively. Two injectors (125 ��m deep and 250 ��m wide) are located on separate sides of the channel, with one downstream 2 mm (equivalent to two main channel widths or eight injector widths) from the other. This results in an asymmetric mixing as the flow proceeds downstream. A dye solution is used to map local mixing throughout the channel by measuring concentration variations as a function of both space and time. The primary flow rates are varied from 0.01 to 0.20 ml/min (Reynolds numbers of 0.3 to 26.6), the injector flow rate ratios are varied from 0.125 to 2, and the pulsing frequencies are varied from 5 to 15 Hz. Images of the concentration variations within the channel are used to quantify mixing by calibrating the intensity of the image with the concentration of the dye solution. The degree of mixing (DoM) is used as a measure of quality and is defined based on the integration across the channel of the difference between the local concentration and the 50% concentration values. DoM is normalized by the 50% concentration value and subtracted from one to yield a parameter that varies from 0 (no mixing) to 1 (perfect mixing). It is shown that there is a high degree of repeatability of concentration distribution as a function of phase of the pulsing cycle. A mixing map is constructed over the range of variables tested which indicates an optimum set of flow and pulsing conditions needed to achieve maximum mixing in the main channel flow. The flow rate ratio between the injectors and main channel is found to be the most influential parameter on overall mixing. The highest DoM in the main channel was found to be 0.89. It is also noticed that improved mixing can occur at very low flow ratios under a unique set of primary flow and low frequency pulsing conditions. In general, there is an inverse relationship between primary flow rate and pulsing frequency to achieve better overall mixing. / Graduation date: 2003

This thesis focuses on the study of the size effect in the elastic-viscoplastic response of pure face centered cubic polycrystalline materials. First, the effect of vacancy diffusion is studied via the use of a two-phase self-consistent scheme in which the inclusion phase represents grain interiors and the matrix phase represents grain boundaries. The behavior of the inclusion phase is driven by the activity of dislocations, described with typical strain hardening laws, and by the activity of Coble creep. The behavior of the matrix phase is modeled as elastic-perfect plastic. This model is then extended to account for the possible activity of Lifschitz sliding. The active role of grain boundaries to the viscoplastic deformation is studied with the introduction of a novel method allowing the scale transition from the atomistic scale to the macroscopic scale. A model describing the mechanism of grain boundary dislocation emission and penetration is informed with molecular simulations and finite element simulations. The macroscopic response of the material is then predicted with use of several self-consistent schemes, among which two novel three-phases schemes are introduced. The most refined micromechanical scheme proposed is based on a two-phase representation of the material and is valid in the elastic-viscoplastic regime and accounts for the effect of slightly weakened interfaces.

The deleterious effect of moisture on the structural integrity of asphalt mixtures has been recognized as one of the main causes of early deterioration of asphalt pavements. This phenomenon, usually referred to as moisture damage, is defined as the progressive loss of structural integrity of the mixture that is primarily caused by the presence of moisture in liquid or vapor state. Moisture damage is associated with the development of different physical, mechanical, and chemical processes occurring within the microstructure of the mixture at different intensities and rates. Although there have been important advancements in identifying and characterizing this phenomenon, there is still a lack of understanding of the damage mechanisms occurring at the microscopic level. This situation has motivated the research work reported in this dissertation. The main objective of this dissertation is to formulate and apply a numerical micromechanical model of moisture-induced damage in asphalt mixtures. The model focuses on coupling the effects of moisture diffusion—one of the three main modes of moisture transport within asphalt mixtures—with the mechanical performance of the microstructure. Specifically, the model aims to account for the effect of moisture diffusion on the degradation of the viscoelastic bulk matrix of the mixture (i.e., cohesive degradation) and on the gradual deterioration of the adhesive bonds between the aggregates and the asphalt matrix (i.e., adhesive degradation). The micromechanical model was applied to study the role of some physical and mechanical properties of the constitutive phases of the mixtures on the susceptibility of the mixture to moisture damage. The results from this analysis suggest that the diffusion coefficients of the asphalt matrix and aggregates, as well as the bond strength of the aggregate-matrix interface, have the most influence on the moisture susceptibility of the mixtures. The micromechanical model was further used to investigate the influence of the void phase of asphalt mixtures on the generation of moisture-related deterioration processes. Two different probabilistic-based approaches were used to accomplish this objective. In the first approach, a volumetric distribution of air voids sizes measured using X-Ray Computed Tomography in a dense-graded asphalt mixture was used to generate probable void structures in a microstructure of an asphalt mixture. In the second approach, a stochastic modeling technique based on random field theory was used to generate probable air voids distributions of the mixture. In this second approach, the influence of the air voids was accounted for by making the physical and mechanical properties of the asphalt matrix dependent on probable voids distributions. Although both approaches take into consideration the characteristics of the air void phase on the mechanical response of the mixtures subjected to moist environments, the former explicitly introduces the air phase within the microstructure while the latter indirectly includes its effects by modifying the material properties of the bulk matrix. The results from these simulations demonstrated that the amount, variability and location of air voids are decisive in determining the moisture-dependent performance of asphalt mixtures. The results from this dissertation provide new information on the kinetics of moisture damage mechanisms in asphalt mixtures. In particular, the results obtained from applying the micromechanical model permitted identification of the relative influence of the characteristics of the constitutive phases of a mixture on its moisture-related mechanical performance. This information can be used as part of design methodologies of asphalt mixtures, and/or as an input in life-cycle analysis models and maintenance programs of road infrastructure.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

The work presented in this dissertation is focused on integrating organic transistor based circuits with planar microfluidic devices for discrete droplet handling. Discrete droplet based microfluidic systems are being increasingly investigated for lab-on-a-chip type applications. An essential component of a lab-on-a-chip system is the drive circuitry that runs the system. Conventionally, a variety of schemes have been implemented for acting as drivers for microfluidic devices. Organic transistor based circuits offer a viable and cost-effective option for serving as drivers for planar microfluidic devices. The magnitudes of voltages and the time scales involved in implementing these discrete droplet based systems are in good agreement with the values of voltages that can be reliably generated using organic transistor based circuits. Thus, the union of two cost-effective technologies with the ability to perform a wide variety of functions in a lab-on-a-chip type system would be highly desirable. A simple, planar microfluidic device with an open structure is implemented on a glass substrate. The device is optimized for reliable and repeatable performance using Cytop as the insulating dielectric. Cytop provides a highly hydrophobic surface for reversible wetting to take place on the application of electrical voltage. Various organic transistor based circuits are fabricated using Pentacene as the p-type semiconducting material and N,N'-bis(n-octyl)-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI-8CN₂) as the n-type material. A top contact inverter, which is the most basic complementary metal oxide semiconductor circuit is fabricated and used as the driver for the planar microfluidic device. The output voltages generated by the inverter are used to actuate discrete water droplets over adjacent electrodes and also to perform merging of droplets, which is another basic functional operation that is performed on lab-on-a-chip type assemblies. Reliable and repeatable performance of the microfluidic device as well as the CMOS circuit is achieved. This work presents the first implementation of a discrete droplet based device driven by electrical voltages generated by an organic transistor based circuit. The physical mechanisms that are responsible for the motion of droplets have been investigated and contributions from electrowetting forces and dielectrophoretic forces have been resolved.

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