Electroosmotic flows are extensively employed for fluid transport and sample separation in lab-on-a-chip technologies, capillary zone electrophoresis, and generally in channels and capillaries with length scales on the order of 100 microns or less. Experimental flow imaging has determined the disruption of the plug flow profile as a result of inhomogeneities in the capillary wall surface. These effects generally consist of parabolic flow profiles replacing the plug flow, and result in the Taylor dispersion of samples being transported by the flow. It is important to quantify the levels of dispersion to optimize separation and transport technologies. In this paper, molecular diffusion effects are incorporated into the random zeta potential model of Gleeson [JCIS 2002] by following the Taylor dispersion methodology of Stone and Brenner [Ind. Eng. Chem. Res. 1999]. It is shown that effective dispersion coefficients may be obtained under certain circumstances, and the application of such simplified models to dispersion and zone spreading in microfluidic devices is discussed.
Journal: TechConnect Briefs
Volume: 2, Technical Proceedings of the 2004 NSTI Nanotechnology Conference and Trade Show, Volume 2
Published: March 7, 2004
Pages: 375 - 378
Industry sector: Sensors, MEMS, Electronics
Topics: MEMS & NEMS Devices, Modeling & Applications