Date of Award

Spring 2011

Document Type


Degree Name

Doctor of Philosophy (PhD)


Aerospace Engineering

Committee Director

Shizhi Qian

Committee Member

Oktay Baysal

Committee Member

Ali Beskok

Committee Member

Yan Peng


Electrokinetics has been widely used to propel and manipulate particles in micro/nano-fluidics. The first part of this dissertation focuses on numerical and experimental studies of direct current (DC) electrokinetic particle transport in microfluidics, with emphasis on dielectrophoretic (DEP) effect. Especially, the electrokinetic transports of spherical particles in a converging-diverging microchannel and an L-shaped microchannel, and cylindrical algal cells in a straight microchannel have been numerically and experimentally studied. The numerical predictions are in quantitative agreement with our own and other researchers' experimental results. It has been demonstrated that the DC DEP effect, neglected in existing numerical models, plays an important role in the electrokinetic particle transport and must be taken into account in the numerical modeling. The induced DEP effect could be utilized in microfluidic devices to separate, focus and trap particles in a continuous flow, and align non-spherical particles with their longest axis parallel to the applied electric field. The DEP particle-particle interaction always tends to chain and align particles parallel to the applied electric field, independent of the initial particle orientation except an unstable orientation perpendicular to the electric field imposed.

The second part of this dissertation for the first time develops a continuum-based numerical model, which is capable of dynamically tracking the particle translocation through a nanopore with a full consideration of the electrical double layers (EDLs) formed adjacent to the charged particles and nanopores. The predictions on the ionic current change due to the presence of particles inside the nanopore are in qualitative agreement with molecular dynamics simulations and existing experimental results. It has been found that the initial orientation of the particle plays an important role in the particle translocation and also the ionic current through the nanopore. Furthermore, field effect control of DNA translocation through a nanopore using a gate electrode coated on the outer surface of the nanopore has been numerically demonstrated. This technique offers a more flexible and electrically compatible approach to regulate the DNA translocation through a nanopore for DNA sequencing.