Identifier

etd-11162005-182307

Degree

Master of Science (MS)

Department

Mechanical Engineering

Document Type

Thesis

Abstract

Passive (diffusional) mixing has been used in designing high-aspect-ratio micro-mixers for the purpose of performing the Liagase Detection Reaction (LDR). A simple model was used to design such mixers optimized for pressure drop or time required to deliver a prescribed volume of mixture. The types of mixers considered are simple, cheap, and durable and can perform over a broad range of volumetric flow rates at reasonably modest pressure drops. The fluids typically have a very low diffusion coefficient of=1.2x10^10m^2/s, and thus diffusional mixing can only be effective in high-aspect-ratio micro-channels. A realizable aspect ratio of 6 has been considered initially because it is easily releasable using the LIGA technique. Numerical simulations were performed on various diffusional-based micromixer configurations. Two variants of a Y-type mixer with contraction and several variants of a mixer employing jets in cross-flow have been simulated. The various mixers have been evaluated in terms of volumetric mixing efficiencies and maximum pressure drops. One of the mixers with jets-in-cross-flow was found to perform best. In addition, the effect of jet width and expansion after the mixing were assessed. Experimental validations for the jets-in-cross-flow mixer were performed. The mixer was manufactured using a micromilled brass mold insert hot embossed into a Polymethyl-methacrylate (PMMA) substrate, which was then covered with 0.125mm PMMA coverslip. A chemiluminescence technique was applied for the first time to make Qqualitative observations of the mixing zones. Quantitative mixing efficiency experiments were performed by using Rhodamine B fluorescent dye solution and de-ionized water. The experimental results show good agreement with numerical simulations.

Date

2005

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Dimitris E. Nikitopoulos

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