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Microparticle Influenced Electroosmotic Flow Microparticle Influenced Electroosmotic Flow

by Young, John M

Abstract (Summary)
The influence of microparticles on electroosmotic flow was investigated experimentally and numerically. Experiments were conducted using four different particle types of varying chemical composition, surface charge and polarity. Each particle type was tested at five different volume fractions ranging from 0.001 – 0.025. With a constant applied electric field, positively charged particles enhanced the electroosmotic flow by as much as 850%. The enhancement depended on particle composition, size and concentration. For negatively charged particles, the bulk electroosmotic flow was retarded with the largest reductions being 35%. This occurred for the greatest negative paricle concentration studied. A final experimental study utilizing a single volume fraction and particle type was conducted using microtube inner diameters of 100 – 300 micrometers. It was found that the effective electroosmotic mobility decreases with increasing microtube diameter. A numerical study of microparticle influenced electroosmotic flow was also conducted for positively and negatively charged particles. A Galilean transformation was employed in which the particles were held stationary. A moving wall model was utilized to account for the particle velocity and the wall-induced electroosmotic flow. The particle-induced electroosmotic flow was also accounted for. A range of particle velocities were imposed in order to study the flow physics for a range of potential flows. Scenarios were run for a single tube diameter of 100 micrometers and a single particle diameter of 1.7 micrometers. Volume fractions of 0.001, 0.0075 and 0.025 were tested for both positively and negatively charged particles. At least two particle charges were studied for each volume fraction and polarity. Comparisons of the trends in the numerical model are qualitatively compared with the trends in the experimental data. The numerical and experimental data demonstrated similar trends. For positively charged particles, an increase in volume fraction showed a nonlinear increase in the average bulk flow velocity. For negatively charged particles an increase in volume fraction showed a nonlinear decrease in the average bulk flow velocity.
Bibliographical Information:

Advisor:

School:Brigham Young University

School Location:USA - Utah

Source Type:Master's Thesis

Keywords:electroosmosis electrophoresis electrokinetics microchannels microparticles

ISBN:

Date of Publication:05/26/2005

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