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No description available.

The propagation of stress within a granular material has been studied for many years, but only recently have models and theories focused on the micromechanical (single grain) level. Experiments at this level are still rather limited in number. For this reason, a system using optical techniques has been developed. The substrate on which the granular bed is assembled is a double layer elastic substrate with high modulus epoxy constituting the top layer and silicone rubber as the bottom layer. In between the two layers, gold is coated which acts as a reflective film. To design the substrate, a Finite Element Analysis package called LUSAS was used. By performing a non-linear contact analysis, the design of the substrate was optimised so as to give a linear response, high stiffness, deflection in the measurable range, and negligible cross-talk between neighbouring grains. Fabrication and inspection techniques were developed to enable samples to be manufactured to this design. The deformation of the gold interface layer is measured using interferometry. The interferometer utilised a frequency tunable laser which acts both as the light source and the phase shifting device. The optical arrangement is based on the Fizeau set-up. This has removed several problems such as multiple reflections and sensitivity to vibration that occurred when using a Mach-Zehnder configuration. A fifteen-frame phase shifting algorithm, was developed based on a Hanning window, which allows the phase difference map to be obtained. This is then unwrapped in order to obtain the indentation profile. The deflection profile is then converted to a single indentation depth value by fitting a Lorentzian curve to the measured data. Calibration of the substrate is carried out by loading at 9 different locations simultaneously. Spatial and temporal variations of the calibration constants are found to be of order 10-15%. Results are presents showing contact force distributions under both piles of sand and under face-centred cubic arrangements of stainless steel balls. Reasonable agreement was obtained in the latter case with both the expected mean force and the probability density function predicted by the so-called 'q' model. The experimental techniques are able to measure small displacements down to a few nanometers. To the best of my knowledge these experiments are the first to employ the interferometer method in attempting to measure the contact force distribution at the base of a granular bed.

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Garmestani, Hamid, Committee Member ; Johnson, Steven, Committee Chair ; McDowell, David, Committee Member ; Qu, Jianmin, Committee Co-Chair ; Cherkaoui, Mohammed, Committee Co-Chair.

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by Chow Wing Yin, Winnie. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 74-78). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.ii / ACKNOWLEDGEMENTS --- p.iii / TABLE OF CONTENTS --- p.iv / LIST OF FIGURES --- p.vi / LIST OF TABLES --- p.viii / Chapter 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Digital Microfluidics --- p.1 / Chapter 1.2 --- Soft Lithography of Polymer --- p.2 / Chapter 2 --- ELECTROCAPILLARY-BASED MICROACTUATION --- p.5 / Chapter 2.1 --- Surface Tension in Microscale --- p.5 / Chapter 2.2 --- thermocapillary-based microactuation --- p.6 / Chapter 2.3 --- electrocapillary-based microactuation --- p.6 / Chapter 2.3.1 --- Continuous Electrowetting (CEW) --- p.7 / Chapter 2.3.2 --- Electrowetting (EW) --- p.8 / Chapter 2.3.3 --- Electrowetting-On-Dielectric (EWOD) --- p.11 / Chapter 3 --- SOFT LITHOGRAPHY --- p.14 / Chapter 3.1 --- Rapid Prototyping --- p.15 / Chapter 3.2 --- Replica Molding --- p.16 / Chapter 3.2.1 --- Pouring Method --- p.17 / Chapter 3.2.2 --- Sandwich Molding Method --- p.17 / Chapter 3.2.3 --- Spin On Method --- p.18 / Chapter 3.3 --- Sealing --- p.20 / Chapter 3.3.1 --- Reversible Sealing --- p.20 / Chapter 3.3.2 --- Irreversible Sealing --- p.20 / Chapter 3.4 --- Multilayer Fabrication --- p.21 / Chapter 4 --- METAL DEPOSITION --- p.22 / Chapter 4.1 --- Gold Deposition by Sputtering Method --- p.22 / Chapter 4.1.1 --- Gold Deposition on PMMA --- p.22 / Chapter 4.1.2 --- Gold Deposition on PDMS --- p.23 / Chapter 4.2 --- ITO Deposition by Sputtering Method --- p.26 / Chapter 4.2.1 --- Image Patterning of ITO --- p.27 / Chapter 5 --- POLYMER-BASED SUBSTRATES BONDING USING PDMS --- p.29 / Chapter 5.1 --- Design of Microfluidic System --- p.29 / Chapter 5.1.1 --- PDMS --- p.29 / Chapter 5.1.2 --- Design of the Vortex Micropump --- p.30 / Chapter 5.2 --- Fabrication of Microfluidic System --- p.31 / Chapter 5.2.1 --- Micro Impeller Fabrication Process --- p.31 / Chapter 5.2.2 --- Micro Patterning of PMMA by Hot Embossing Technique --- p.32 / Chapter 5.2.3 --- Assembly of Micropump by PDMS Bonding Process --- p.34 / Chapter 5.3 --- Experimental Results --- p.36 / Chapter 5.3.1 --- Tensile Bonding Test --- p.36 / Chapter 5.3.2 --- Leakage Test --- p.38 / Chapter 6 --- DIGITAL MICROFLUIDICS IN MICROCHANNEL --- p.39 / Chapter 6.1 --- Digital Microfluidics --- p.39 / Chapter 6.2 --- Design of the MicroChannel --- p.39 / Chapter 6.3 --- Materials of the MicroChannel --- p.42 / Chapter 6.3.1 --- Substrate --- p.42 / Chapter 6.3.2 --- Adhesion Layer --- p.42 / Chapter 6.3.3 --- Electrode --- p.43 / Chapter 6.3.4 --- Dielectric Layer --- p.43 / Chapter 6.4 --- Fabrication of the MicroChannel --- p.44 / Chapter 7 --- EXPERIMENTAL RESULTS --- p.46 / Chapter 7.1 --- ewod on pdms layer --- p.46 / Chapter 7.2 --- PDMS Parallel Plate Channel --- p.48 / Chapter 7.2.1 --- Contact Angle --- p.49 / Chapter 7.3 --- Parylene C Parallel Plate Channel --- p.52 / Chapter 7.4 --- Sealed pdms MicroChannel --- p.54 / Chapter 7.5 --- Driving Pressure --- p.55 / Chapter 7.6 --- microchannel in the vertical position --- p.57 / Chapter 8 --- FUTURE WORK --- p.60 / Chapter 8.1. --- Digital Microfluidic Circuit Design --- p.60 / Chapter 8.1.1. --- Electrodes Design --- p.61 / Chapter 8.2. --- Fabrication Process --- p.63 / Chapter 9 --- SUMMARY --- p.64 / APPENDIX A --- p.67 / BIBLIOGRAPHY --- p.74

Lam Raymond Hiu-wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 87-91). / Abstracts in English and Chinese. / Abstract --- p.ii / Abstract (Chinese) --- p.iv / Acknowledgment --- p.v / Contents --- p.vii / List of Figures --- p.ix / Introduction --- p.1 / Chapter 1-1 --- Overview of MEMS and Microfluidic Technologies --- p.1 / Chapter 1-1-1 --- Microelectromechanical Systems (MEMS) --- p.1 / Chapter 1-1-2 --- Microfluidic Systems --- p.2 / Chapter 1-2 --- Literture Review on Microfluidic Devices --- p.4 / Chapter 1-2-1 --- Micropumps --- p.4 / Chapter 1-2-2 --- Microvalves --- p.5 / Chapter 1-2-3 --- Micromixers --- p.5 / Chapter 1-2-3 --- Integration of Multiple Devices: Microfluidic Systems --- p.6 / Chapter 1-3 --- Motivation and Research Objectives --- p.7 / Chapter 1-4 --- Thesis Outline --- p.9 / Fluid Flow in MicroChannel --- p.11 / Chapter 2-1 --- Velocity Profile in a MicroChannel --- p.11 / Chapter 2-2 --- Pressure Dissipation by Laminar Friction --- p.16 / Chapter 2-3 --- Bubble Filtering --- p.20 / Microfluidic Centrifugal Pumping --- p.23 / Chapter 3-1 --- Vortex Micropump --- p.23 / Chapter 3-1-1 --- Operation Principle and Device Design --- p.23 / Chapter 3-1-2 --- Alternative Pump Design --- p.25 / Chapter 3-2 --- Micropump Fabrication --- p.27 / Chapter 3-2-1 --- Electroplated Impeller --- p.27 / Chapter 3-2-2 --- SU-8 Impeller --- p.30 / Chapter 3-2-3 --- Micropump Fabricated by Micro Molding Replication Technique --- p.32 / Chapter 3-2-4 --- Inverted-chamber Vortex Micropump --- p.35 / Chapter 3-3 --- Elementary Centrifugal Pump Theory --- p.36 / Chapter 3-3-1 --- Pumping Pressure and Discharge --- p.36 / Chapter 3-3-2 --- Fluid Horsepower --- p.38 / Chapter 3-3-3 --- Effect of Blade Angle --- p.40 / Chapter 3-4 --- Pumping Specification --- p.41 / Mixing Based on Mechanical Vibration --- p.47 / Chapter 4-1 --- Micromixer Design --- p.47 / Chapter 4-1-1 --- Oscillating Diaphragm Actuated Microfluidic Mixing --- p.47 / Chapter 4-1-2 --- Flat-surface Diaphragm Active Micromixer --- p.48 / Chapter 4-1-3 --- Mixing Enhancement by Pillared Chamber Profile --- p.50 / Chapter 4-2 --- Fabrication Process --- p.52 / Chapter 4-2-1 --- Flat-surface Diaphragm Active Micromixer --- p.52 / Chapter 4-2-2 --- Pillared-surface Diaphragm Active Micromixer --- p.54 / Chapter 4-3 --- Experimental Analysis of Mixing Performance --- p.56 / Microfluidic Flow Planning System --- p.63 / Chapter 5-1 --- System Design --- p.63 / Chapter 5-1-1 --- Chip Design and Fabrication --- p.63 / Chapter 5-1-2 --- Digital Controlling System --- p.65 / Chapter 5-1-3 --- Operation Mechanism --- p.67 / Chapter 5-2 --- Experimental Results --- p.69 / Microfluidic Mixing Module Array --- p.70 / Chapter 6-1 --- System Configuration --- p.70 / Chapter 6-1-1 --- Microfluidic Chip Design --- p.70 / Chapter 6-1-2 --- Backward Flow Elimination by Tesla Valve --- p.72 / Chapter 6-1-3 --- System Controller and Operation Mechanism --- p.75 / Chapter 6-2 --- Fabrication --- p.76 / Chapter 6-3 --- Mixing Ratio Estimation --- p.78 / Chapter 6-4 --- Experimental Results --- p.79 / Conclusion --- p.81 / Future Work --- p.83 / Chapter 8-1 --- Self Driven Microfluidic Flow Planning System --- p.83 / Chapter 8-2 --- Mixing Enhancement by Cavitation Microstreaming --- p.84 / References --- p.87 / Bonding Test on UV-curing Epoxy Resin --- p.92 / Circuit Schematic of Digital Controller --- p.94 / Advanced Digital Microfluidic Controller --- p.97

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