Theoretical analysis of the electrokinetic pumping of non-Newtonian fluids

CLAUDIO L. A. BERLI

New York, USA

Congreso; 13th International Conference on Surface and Colloid Science; 2009

International Asociacion of Colloid and Interface Scientists

Electrokinetic pumping is a well-known method to transport fluids through microchannels. Research in the field is now motivated by microfluidic applications, where fully integrated micropumps are desirable. Most of the papers found in the literature involve solutions of simple electrolytes, the viscosity of which is a constant coefficient. The present work discusses theoretical predictions of the flow rate and output pressure attained when non-Newtonian fluids like polymer solutions are pumped electrokinetically through cylindrical and slit microchannels. The constitutive model of Oswald-de Waele is used to express the shear stress in terms of the velocity gradient. Further, the cases of uniform polymer concentration and wall depletion are considered separately. It is observed that the flow rate is non-linear with both the applied electric field and the back-pressure. Additional contributions to the velocity also arise due to coupling of non-Newtonian and electrokinetic effects. From the technological point of view, a relevant prediction is that the output pressure may be several times higher than that obtained with simple electrolytes, for a given flow rate. These results are also of interest for the design of microfluidic devices that manipulate colloids and polymeric fluids.