The apparent hydrodynamic slip of polymer solutions and its implications in electrokinetics

Abstract

The apparent hydrodynamic slip of polymer solutions is a result of polymer depletion at channel walls, and its fluid dynamic effects are well known. This work reviews the evidences of apparent slip in electrokinetics, and discusses practical consequences in the following fields: (i) electrokinetic transport of polymer solutions in microchannels, which is of interest for the design and operation of microfluidic chips, particularly for electrophoresis; (ii) electroosmotic pumping, where it has been observed that the employment of polymer solutions greatly enhances the output pressure; and (iii) electrokinetic energy conversion, where the apparent slip also contributes to improve the conversion efficiency. In all cases, critical discussions are taken from basic physical concepts.