Date of Graduation

8-2009

Document Type

Thesis

Degree Name

Master of Science in Microelectronics-Photonics (MS)

Degree Level

Graduate

Department

Microelectronics-Photonics

Advisor/Mentor

Ingrid Fritsch

Committee Member

David W. Paul

Second Committee Member

Steve Tung

Third Committee Member

Kenneth G. Vickers

Keywords

Diffusion layers, Magnetic forces, Microfluidics, Passive conductors, Redox magnetohydrodynamics

Abstract

Lab-on-a-chip technologies offer the possibility of developing analytical devices that are low-cost, portable, disposable, fast, and operable by non-technical personnel. Such devices require automated methods to manipulate ultra-small volumes (picoliters) of samples and solution, including pumping, stirring, and positioning. Current methods for ultra-small volume microfluidics have limitations that restrict their use including high voltage requirements, disadvantageous flow profiles or rates, and relatively complicated fabrication due to mechanical parts. Redox magnetohydrodyanmics (RMHD) that utilizes permanent magnets for portability shows promise as a micropump with ease of switching flow direction, no moving parts, compatibility with both aqueous and non-aqueous solutions, low voltages (10-100 mV), and ability to easily pump in a loop. But its fundamentals, including the forces involved and what factors affect the flow profile, must be better understood before its full potential can be realized. Fluid flow in both cells and channels for RMHD systems utilizing high concentration of redox species in supporting electrolyte was investigated. The effects of the placement of walls of the cell and passive (unbiased) conductors relative to active electrodes on fluid flow using RMHD in cells provided evidence that the magnetic force resides primarily in the diffusion layer in these systems, not in the electrolyte between the counter and working electrodes. The effects of channel and working electrode geometry also supported this conclusion. The outcome has important ramifications in designing microfluidic devices that employ RMHD as the pumping method and in the simulation of RMHD.

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