Date of Award

5-2008

Degree Type

Thesis

Degree Name

Master of Science

Major

Electrical Engineering

Major Professor

Jie Wu

Committee Members

Benjamin J. Blalock, Kenneth D. Kihm

Abstract

AC electrokinetics (ACEK) is a promising technique to manipulate micro/bio-fluids and particles. It has many advantages over DC electrokinetics for its low applied voltage, portability and compatibility for integration into lab-on-a-chip devices. This thesis focuses on the design of a multi-functional orthogonal microelectrode system that induces ACEK effect for manipulation of microfluids and particles. Orthogonal electrode configuration used in this research can achieve maximum non-uniform electric field distribution, resulting in strong fluid and particle motion. In the experiments, three types of microflow fields were observed by changing the applied electric signals. Three ACEK processes, capacitive electrode polarization, Faradaic polarization, and AC electrothermal effect are proposed to explain the different flow patterns, respectively. Equivalent circuit model extracted from the impedance measurement helps to determine the optimal condition for ACEK implementation. Both numerical simulation and experimental results are presented and discussed in this thesis. Well controlled ACEK flow help transport target cells to the trapping site, which greatly enhanced the trapping efficiency by dielectrophoresis (DEP), thus long range particle manipulation can be achieved. Together with ACEK effect and pressure driven mechanism, a flow-through system based on orthogonal electrodes is created, which can be used to pump fluids and concentrate bio-particles so as to be able to handle solutions in large volume with low concentration. This simple and easily fabricated setup can be integrated as one component to form potential lab-on-a-chip devices.

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