Fluid rheological effects on electroosmotic flow in a constriction microchannel*

Electroosmotic flow is the method of choice for transport fluids and samples (along with electrophoresis if charged) in micro- and nanofluidic devices. However, the study of electroosmotic flow has to date been mainly focused on Newtonian fluids despite the fact that many of the chemical and biological fluids exhibit non-Newtonian characteristics. We present in this work a systematic experimental study of the fluid rheological effects on electroosmotic flow of viscoelastic solutions in a constriction microchannel. We find that the fluid elasticity effect does not change significantly the electroosmotic flow pattern while the fluid shear-thinning effect may cause pairs of fluid circulations before to after the channel constriction.