AbstractsBiology & Animal Science

To break the limit of the knowledge of the induced-charge electroosmotic flow, this thesis provides a new theoretical and numerical study of the polarizability-dependent induced-charge electroosmotic flow (ICEOF) of dielectric particles. We derived the analytical expression of the induced surface potential on dielectric particles for the first time. Based on this solution, we conducted numerical investigation of the migration of homogeneous and inhomogeneous dielectric particles under the influence of the polarizability-dependent ICEOF. Corresponding applications were also studied and addressed. We found interesting electrokinetic effects associated with the polarizability-dependent ICEOF. It is proved that the electrokinetic motion of single homogeneous particles is not affected by the ICEOF around the particles; however, the hydrodynamic interaction between the ICEOF around two closely located particles is sensitive to the polarizability of the particles. We also studied the ICEOF of heterogeneous particles consisting of multiple dielectric parts. The spatially varying ICEOF around a heterogeneous particle continuously generates a torque. At the same time, the linear slipping velocity on the particle gives rise to constant translational motion. Thus these heterogeneous particles move like micro-wheels. Two novel particle separation methods based on the polarizability-dependent ICEOF were developed and studied numerically. The first is to separate homogeneous particles. A separation region was created in a channel by embedding a pair of conducting plates where strong vortexes were generated after applying electric fields. Due to the hydrodynamic interaction between the ICEOF around particles and the nearby wall, particles can either pass by or be trapped into the vortexes. We further developed a separation method for Janus particles whose surface has two different dielectric properties. The asymmetric ICEOF drives the particle to rotate until line up with the electric field. Meanwhile, the interactions between the ICEOF and the walls locate the particle at an equilibrium distance from the wall depending on the polarizability ratios of the particles. As a result, Janus particles of different polarizability ratios can be collected into different outlet branches continuously and independently. The third application is the new self-propelled particle. A heterogeneous particle is assembled with two differently high-polarizable ends. Under a uniform electric field, the ICEOF around the two polarizable ends results in a driving force pointing to the lower-polarizable end and this driving effect was found a function of the polarizabilities of the two ends. Over all, this thesis for the first time provides the mathematical description of the dependence of ICEOF on the polarizability of the particles. The fact that the strength of ICEOF varies with the polarizability of the particle gives rise to several new particle manipulation techniques. The new particle separation methods were proved more advantageous than their…