Date of Award

8-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Bioengineering

Advisor

Zhang, Guigen

Committee Member

Dean , Delphine

Committee Member

Wang , Pingshan

Abstract

Dielectrophoresis (or DEP) is an important phenomenon which is induced when a dielectric particle is placed in a non-uniform electric field. The force generated by DEP has been exploited for various micro and nano fluidics applications like positioning, sorting and separation of particles involved in medical diagnostics, drug discovery, cell therapeutics, biosensors, microfluidics, nanoassembly, particle filtration etc. The integration of DEP systems into the microfluidics enables inexpensive, fast, highly sensitive, highly selective, label-free detection and also the analysis of target bioparticles.

This work aims to provide a complete compilation of the factors affecting the DEP force. It elucidates the underlying mechanisms using COMSOL Multiphysics and sheds new insight into the mechanisms for the separation and sorting of different types of particles. This research identifies the problems in the literature and uses COMSOL to analyze the impact of these problems on the end results. It examines four factors that affect the DEP force: physical conditions, electrode setup, properties of the particles and suspension medium. Moreover, it analyzes the influence of the Clausius-Mossotti factor (CM factor) and its cross-over upon the magnitude and direction of the DEP force.

From the analysis, it becomes clear that particle size not only affects the magnitude of the DEP force but also the conductivity of the particle. This factor, which is largely ignored, could lead to a shift in the crossover frequency. Shell model plays an important role in determining the dielectric properties of particles that are not homogenous. In such a situation assuming uniform dielectric properties may lead to inconclusive results. The presence of an electric double layer surrounding a particle affects the conductivity of the particle. Also, assuming DEP force to be the only force acting on a particle suspended in a non-uniform electric field leads to errors in the end results.

This research provides knowledge on the basic characteristics of the DEP force and its mechanism. It provides a better understanding by examining numerous works carried out in the past and brings out the problems and their consequences.

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