Electrophoretic velocity of spherical particles in Quemada fluids

Abstract

The biomicrofluidic devices utilizing electrophoresis for sample manipulation are usually encountered with non-Newtonian behavior of working fluids. Hence, developing theoretical models capable of predicting the electrophoretic velocity of colloidal particles in non-Newtonian fluids is of high importance for accurate design and active control of these devices. The present investigation is dealing with the electrophoresis of a spherical particle in a biofluid obeying the Quemada rheological model. The sphere radius is considered to be significantly larger than the Debye length. Moreover, it is assumed that the particle zeta potential is small so that the Debye–Hückel linearization is allowable. An approximate analytical solution is obtained for the particle electrophoretic velocity for the conditions that the deviations of the fluid rheological behavior from the predictions of the Newton's law of viscosity are small. A parametric study along with inspection of some practical examples assuming the blood as the working fluid reveals that the non-Newtonian contribution to the electrophoretic velocity is comparable with the Newtonian part and therefore cannot be neglected. It is observed that the non-Newtonian part of electrophoretic velocity is an increasing function of the hematocrit level and the Deborah number and is independent of the particle size.