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Licentiate seminar

Numercial modeling of dielectrophoresis


Defendant Main Advisor Extra Advisor Date
Yuan Lin Gustav Amberg 2006-06-07

Opponent
OLof Runborg, School of Computer Science and Communication, KTH

Evaluation committee

Abstract

We investigate the dielectrophoretic separation of microparticles. Two di®er- ent models are formulated in two characteristic time scales. The ¯rst model mainly accounts for the orientation behavior and rotational motion of non- spheric microparticles. The concept of e®ective charge is suggested to calcu- late the ¯nite size non-spheric particles. It is combined with the °uid particle dynamics method to calculate hydrodynamic as well as dielectrophoretic forces and torques. The translational motion and the particle-particle interaction are calculated also, but they take much longer time to be observed due to the di®erent time scales of the rotational and translational motions By viewing the particle as spheres, the second model focus on the trans- lational motion of spheres. The hydrodynamic force between particles and particle-particle electrostatic interactions are also taken into account. We check the relative magnitude ratio between these forces in order to determine the importance of these forces. To predict and guide the design of experimental dielectrophoretic separation, two numerical applications are carried out. The ¯rst calculation suggests optimum patterns to improve the trapping e±ciency of E.coli. cells by applying superimposed AC electric ¯elds. The second cal- culation ¯nds out the mobility and separation rate of particles which di®ers in size and electric properties by a multi-step trapping-releasing strategy.
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