Authors: S. Ghosal and Z. Lu
Affilation: Northwestern University, United States
Pages: 68 - 71
Keywords: electroosmosis, electrophoresis, zeta-potential, zone-broadening, dispersion
Electroosmotic flow is often the method of choice for generating fluid flows in micro fluidic devices. The resulting flow has a characteristic at profile which has the advantage of very low axial dispersion. This is only the case, however, if the wall zeta potential is constant. In many applications, the wall zeta potential is variable, either through accident (wall adsorption of analytes) or design (patterned charges). An analytical solution is developed for electroosmotic and pressure driven flows in straight micro fluidic channels of arbitrary cross-sectional shape and distribution of zeta-potential, in the asymptotic limit where variations in the axial direction take place on long length scales compared to a characteristic diameter. A method is provided for computing "effective fluidic impedances" for such inhomogeneous microfluidic channels. The theoretical results are used to explain certain experimental data on CZE in a straight microcapillary.