Electroosmosis in a rectangular microchannel with an inhomogeneous charged surface
Date Issued
2004
Date
2004
Author(s)
Yang, Chung-Wei
DOI
zh-TW
Abstract
The electroosmotic flow of an electrolyte solution in a nonuniformly charged rectangular microchannel is investigated theoretically by considering the case where half of the microchannel wall is positively charged and the other half negatively charged, both are maintained at a constant surface potential. This arrangement leads to a bi-directional electroosmotic flow, which makes design more flexible if the microchannel is used as a microreactor. We show that if the ionic strength is low, the maximal electroosmotic velocity occurs at the center of the microchannel. However, as the ionic strength increases, it shifts towards its corners. This feature is advantageous to reactor design because the nonuniformity problem arising from the slow motion of reactants near corners can be alleviated. The maximal electroosmotic velocity increases with the increase in ionic strength, but reaches a constant value nearly when the ionic strength exceeds a certain level. For a constant cross-sectional area or a constant hydraulic diameter, the electroosmostic volumetric flow as a function of the aspect ratio of the microchannel have a minimum or a maximum. We show that if the pressure gradient is smaller than 104 N/m3, the flow field is dominated by the electrokinetic phenomenon. On the other hand, if the pressure gradient is larger than 104 N/m3, it is dominated by the pressure gradient.
Subjects
電滲透
Electroosmosis
Type
thesis
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