| Two phenomena were studied in this thesis: (1) the relative motion between two or more colloidal particles on an electrode experiencing an ac potential with aqueous electrolyte solutions, and (2) the movement of ions and particles in non-polar liquids in one and two dimensional electric fields.{09}The unifying theme of the work is the use of electric fields to position particles over micron length scales.; In the first part of the thesis, I discuss aggregation or separation of pairs of negatively charged polystyrene latex particles deposited on an electrode under ac polarization. I studied the aggregation experimentally by varying the zeta potential of the particles, the electrolyte composition and concentration, and the frequency of the electrode potential. Trajectories of two adjacent particles were recorded by video-imaging, and analyses were performed to determine the relative velocity between the particles. The relative velocity did not depend on the zeta potential of particles, implying the motion was not electrokinetic in nature. The two-particle dynamics were distinctly different between electrolytes containing bicarbonate ion versus hydroxyl ion; pairs of particles aggregated in bicarbonate solutions at frequencies between 30 and 500 Hz but separated at 1,000 Hz, while the pairs separated with hydroxyl ions at all frequencies up to 1,000 Hz. In all cases the relative velocity between a pair of particles was relatively independent of electrolyte concentration and the cation of the electrolyte.{09}The lack of dependence of the two-particle dynamics on the zeta potential of the particles suggests that the phenomenon of aggregation/separation is driven by electrohydrodynamics resulting from nonuniform electric fields at the electrode surface, but no model is able to quantitatively fit the experimental results.; The second part of the thesis discusses manipulation of particles in non-polar solutions with dc electric fields. The goal was to understand ion conduction in these fluids and characterize particle motion in response to two-dimensional fields established in a thin film of the fluid. First ion conduction was studied with solutions of OLOA 371 (primarily the amphiphile poly(isobutylene succinimde)) and dodecane confined between two parallel electrodes. (Abstract shortened by UMI.)... |
