Transient electroosmotic flow of Newtonian fluids in a microchannel with heterogeneous zeta potentials at the walls

This paper presents an analytical study of the transient electroosmotic flow for Newtonian fluids through a parallel flat plate microchannel with heterogeneous zeta potentials. The dimensionless mathematical model is based on the Poisson-Boltzmann, mass and momentum conservation governing equations together with the lubrication theory. The distribution of the zeta potentials at the walls obeys to a sinusoidal function, which includes dimensional parameters as Dz that controls the magnitude and polarity of the zeta potentials, being capable to produce slanted velocity profiles and inverse flows. On the other hand, the combination of the phase angle between the sinusoidal functions of the zeta potentials w, the dimensionless parameter of their amplitude Dz , and the parameter that controls the frequency of the sinusoidal functions m, induce additional perturbations on the flow, which is directly related to the dimensionless pressure distribution and to the transient flow field. The transient behavior characteristics of the electroosmotic flow are discussed in terms of the zeta potential variations. It is demonstrated that the results for the transient electroosmotic flow, predict the influence of the main dimensionless parameters above mentioned on the velocity profiles and the streamlines. This work about the perturbations on the electroosmotic flow by heterogeneous zeta potentials, contributes to a better understanding of the transport phenomena in microfluidic devices for future mixing applications.