Doctor of Philosophy (PhD)


Mechanical Engineering

Document Type



Microfluidics has received a great deal of attention in the past decade. The ability of modular microfluidic chips to miniaturize integrate chemical and biological systems (µTAS) can be greatly productive in terms of cost and efficiency. During the design of these modular devices, misalignment of materials, geometrical or both is one of the most common problems. These misalignments can have adverse effect in both pressure driven and electrokinetically driven flows. In the present work, Numerical Simulations have been performed to study the effect of material and geometrical mismatch on the flow behavior and species progression in microfluidic interconnects. In the case of electrokinetic flows, simulations were performed for 13%, 50%, 58% and 75% reduction in the available flow area at the mismatch plane. Correlations were developed to predict the flow rate reduction due to the geometrical mismatch in electrokinetic flows. A 13% flow area reduction was found to be insignificant and did not cause an appreciable sample loss. As the amount of geometrical mismatch increases (i.e. area reduction is more than 40%), it can have a significant effect on the sample resolution and on the flow behavior. In the case of pressure driven flows, Numerical Simulations have been performed for three types of interconnection methods: End-to-End, Channel Overlap, and Tube-in- Reservoir interconnection. The effects of geometrical misalignments in these three interconnection methods have been investigated and the results were interpreted in terms of the pressure drop and equivalent length. The amount of misalignment was varied by changing the available flow area ratios. All the configurations were simulated for practically relevant Reynolds numbers ranging from 0.075 to 75. Correlations were developed to predict the pressure drop for any given misalignment area ratio. It was found that for the misalignment area ratio of 2:1 or more, the increase in pressure drop can be drastic. Numerical simulations of Injection and separation were also performed to study the effect of curvatures on the elongation of generated plugs. These end curvatures are commonly encountered during high precision micromilling process as a method to fabricate polymer microfluidic devices. The effect of pinching and pullback voltages on the generation of the sample plugs was investigated and optimum conditions to minimize plug dispersion were found.



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Committee Chair

Dimitris E. Nikitopoulos