<p>The purpose of the diploma work is to investigate the possibilities to combine three different areas; reflectometry, microfluidics and laser ablation in a microstructured single-mode fiber, thus obtaining a controlled technique for positioning for ablation and collection of liquids from small inclusions.</p><p>Each of the three areas is thoroughly described in different sections of this report. The first part of the experiments in this diploma work consisted of combining reflectometry and microfluidics, the second part combining reflectometry with laser ablation and the final experiment setup consisted of a combination of all three areas. An artificial system for liquid collection was then designed for that purpose.</p><p>The results obtained from experiments and measurements clearly demonstrate that combining reflectometry, laser ablation and fluid collection in a single optical fiber is promising. Future work will include improvements of the technique towards a medical application for bone marrow transplantation.</p>

Microscale fluid processes are an increasingly important subgroup of fluid mechanics. Applications for heat transfer and micro-electro-mechanical devices use flows on the scale of less than one hundred microns. This study is part of a larger work in which a multiphase, high shear environment is studied in a microchannel that has a depth of approximately 130 μm. Velocities are obtained using non-invasive imaging schemes. Laser induced fluorescent Particle Image Velocimetry (PIV) is used to analyze the velocity distribution in the microchannel. Multiple image processing techniques are used to optimize the images for correlation calculations. Velocity profiles for three flow rates and three void fractions (one of which is zero) are developed experimentally. The effect of the microbubbles on the PIV analysis is shown to flatten the profile through one primary mechanism and possibly a secondary, less dominant mechanism. / Graduation date: 2006

An experimental study was performed in which an ammonia-water solution was desorbed within a branching fractal-like microchannel array. The solution entered in the center of a disk, and flowed out radially until discharging in to a gravity-driven separation chamber. Heat was added to the ammonia-water through a thin wall, above which flowed heat transfer oil in a separate branching fractal-like microchannel array. Such arrays have been shown to utilize the increased heat transfer coefficients seen in parallel channel arrays; however, they do so with a lower pressure drop. An experimental flow loop consisting of ammonia-water and heat transfer oil sub-loops was instrumented along with a test manifold for global measurements to be taken. Temperature, pressure, density and mass flow rate measurements permitted calculation of desorption and heat transfer characteristics. Parameters included oil mass flow rate, oil inlet temperature, and strong solution flow rate, while strong solution concentration, temperature, and weak solution pressure were kept constant. The desorber was assumed to achieve equilibrium conditions between the vapor and weak solution in the separation chamber. The exit plenum was large and acted as a flash chamber, making the assumption reasonable. The vapor mass fraction was determined from knowledge of the weak solution saturation temperature. Heat exchanger analyses (LMTD and ε-NTU) were done to determine the heat transfer characteristics of the desorber. Calculated values of UA are shown to be as high as 5.0 W/K, and desorber heat duties were measured as high as 334 W. Strong solution, at 0.30 mass fraction, was desorbed into weak solution and vapor with concentrations ranging from 0.734 to 0.964. Circulation ratios, defined as strong solution mass flow rate per unit desorbed vapor mass flow rate, varied in this study from 3.4 to 20. A method for specifying desorber operating conditions is described, in which a minimum desorber heat input per unit vapor flow rate is determined at an optimum circulation ratio. A description of how the circulation ratio behaves as a function of strong solution mass flow rate, oil flow rate, and the maximum temperature difference between oil and ammonia-water solution is shown. / Graduation date: 2006

Over the last decade, the miniaturization of analytical systems has become an increasingly important and interesting research area. Miniaturized systems offer many advantages, including reduced reagent and sample consumption, shorter analysis times, portability and disposability. This dissertation describes novel approaches in this direction, focusing on two areas: the miniaturization of existing column chromatographic systems and the development of microfluidic systems in which the separation is performed in a channel on a microchip. A new type of methacrylate-based monolithic capillary columns for liquid chromatography and capillary electrochromatography were prepared within the confines of fused-silica tubing using Starburst dendrimers to affect porosity. The polyamidoamine (PAMAM) dendrimers were incorporated into a solution of functionalized monomer, cross-linker, solvents, and polymerization initiator. Thermal polymerization, followed by the removal of solvent and dendrimers, produced a continuous rod of polymer with uniform porosity. Different column porosities were obtained by varying the amount of the dendrimer template. The chromatographic performance of these monolithic columns was evaluated using a peptides mixture obtained by tryptic digestion of chicken egg lysozyme. A distinct advantage of polymer monolithic stationary phases over conventional packed chromatographic beds is the ability to prepare them easily and rapidly via free radical polymerization within the channels of a microfluidic device. In this work, continuous polymeric beds were prepared within a channel of three different microchip substrates: glass, poly(dimethylsiloxane) and polycarbonate. The methacrylate-based monolith was cast in-situ via UV-initiated polymerization. The functionalization of the inner wall of the channel with methacryloyl groups enabled the covalent binding of the monolith to the wall. The morphology of the wall-anchored monolith was studied by SEM of chip sections, and by SEM of an extruded segment of non-anchored monolith from a separate chip. / Graduation date: 2005

Graduation date: 2005

The effect of unsteady thermocapillary convection on the mass transfer rate of a solute between two immiscible liquids within a rectangular microscale channel with differentially heated sidewalls was numerically investigated. A computational fluid dynamic code in Fortran77 was developed using the finite volume method with Marker and Cell (MAC) technique to solve the governing equations. The discrete surface tracking technique was used to capture the location of the moving liquid-liquid interface. The code produced results consistent with those reported in published literature. The effect of the temperature gradients, the aspect ratio, the viscosity of liquid, and the deformation of the interface on the mass transfer rate of a solute were studied. The mass transfer rate increases with increasing temperature gradient. The improvement of the mass transfer rate by the thermocapillary convection was found to be a function of the Peclet number (Pe). At small Pe, the improvement of the mass transfer rate increases with increasing Pe. At high Pe, increasing the Pe has no significant effect on increasing the mass transfer rate. Increasing the aspect ratio of the cavity up to 1 increases the mass transfer rate. When the aspect ratio is higher than 1, the vortex moves only near the interface, resulting in decreasing the mass transfer rate. By increasing the viscosity of the liquid in top phase, the maximum tangential velocity at the interface decreases. As a result, the improvement of the mass transfer rate decreases. The deformation of the interface has no significant effect on the improvement of the mass transfer rate. By placing the heating source at the middle of the cavity, two steady vortices can be induced in a cavity. As a result, the mass transfer rate is slightly enhanced than that in the system with one vortex. By reversing the direction of the temperature gradient, the mass transfer rate decreases due to the decrease in the velocity of bulk fluid. The thermocapillary convection also promotes the overall reaction process when the top wall of the cavity is served as a catalyst. / Graduation date: 2005

A two-dimensional model was developed to predict concentration profiles from passive, laminar mixing of concentration layers formed in a fractal-like merging channel network. Both flat and parabolic velocity profiles were used in the model. A physical experiment was used to confirm the results of the model. Concentration profiles were acquired in the channels using laser induced fluorescence. The degree of mixing was defined and used to quantify the mixing in the test section. Although the results of the experiment follow the trend predicted by the two-dimensional model, the model under predicts the results of the experiment. A three-dimensional CFD model of the flow field in the channel network was used to explain the discrepancies between the two-dimensional model and the experiment. For the channel network considered, the degree of mixing is a function of Peclet number. The effect of geometry on the degree of mixing is investigated using the two-dimensional model by varying the flow length, the width of the inlet channels, and the number of branching levels. A non-dimensional parameter is defined and used to predict an optimum number of branching levels to maximize mixing for a fixed inlet channel width, total length, and channel depth. / Graduation date: 2003

The purpose of the diploma work is to investigate the possibilities to combine three different areas; reflectometry, microfluidics and laser ablation in a microstructured single-mode fiber, thus obtaining a controlled technique for positioning for ablation and collection of liquids from small inclusions. Each of the three areas is thoroughly described in different sections of this report. The first part of the experiments in this diploma work consisted of combining reflectometry and microfluidics, the second part combining reflectometry with laser ablation and the final experiment setup consisted of a combination of all three areas. An artificial system for liquid collection was then designed for that purpose. The results obtained from experiments and measurements clearly demonstrate that combining reflectometry, laser ablation and fluid collection in a single optical fiber is promising. Future work will include improvements of the technique towards a medical application for bone marrow transplantation.

Laser scanning cytometry (LSC) is a slide-based method that is used clinically for Quantitative Imaging Cytometry (QIC). A “Clatch” slide, named after the inventor, which is used in conjunction with the LSC for immunophenotyping patient cell samples, has several drawbacks. The slide requires time consuming and laborious pipette steps, making the slide prone to handling errors. The Clatch slide also uses a significant amount of cell sample, limiting the number of analyses for fine needle aspirate (FNA) samples. This thesis details an automated microfluidic system, composed of an embedded circuit, a plastic and polymer microfluidic device, and an aluminum frame, which can perform the same immunophenotyping procedures. This new system reduces the labor from 36 pipette steps to 8, it reduces the amount of cell sample from 180 μL to 56 μL, and it shortens the entire procedure from 75 minutes to 42 minutes.

In this work, a MFC fabrication procedure including two non-conventional techniques (partial baking and cap-sealing) were employed for the development of an up-scaled microfluidic fuel cell (MFC). Novel carbon-based electrode materials were employed, including carbon foam, fibre, and cloth, the results from which were compared with traditionally-employed carbon paper. The utilization of carbon cloth led to 15% of the maximum power that resulted from carbon paper; however, carbon fibre led to a 24.6% higher power density than carbon paper (normalized by electrode volume). When normalized by projected electrode area, the utilization of carbon foams resulted in power densities up to 42.5% higher than that from carbon paper. The impact of catalyst loading on MFC performance was also investigated, with an increase from 10.9 to 48.3 mgPt cm-2 resulting in a 195% increase in power density.