Effects of fluid shear-thinning on electrokinetic instability in microchannel flows with conductivity gradients

Electrokinetic instability (EKI) arises from the action of electric field on fluid flow with conductivity gradients. It has been extensively studied in Newtonian fluids for the applications of, for example, micromixing and sample stacking. However, very little is known regarding EKI in non-Newtonian fluids. We present in this work a fundamental study of EKI in shear-thinning xanthan gum (XG) solutions through a T-shaped microchannel. The concentration of XG polymer is varied from 0 ppm (corresponding to the case of a Newtonian fluid) to 3000 ppm for the purpose of achieving a range of fluid shear-thinning effects. We examine how the electrokinetic flow pattern of XG solutions develops with the imposed electric field and differs from that of a Newtonian fluid. We also study how the change of XG concentration affects the threshold electric field for the onset of EKI.