The EOF of polymer solutions

Abstract

The EOF of polymer solutions is analysed in the framework of continuum fluid mechanics and the standard electrokinetic model. Two key aspects are taken into consideration: the non-Newtonian character of the fluid and the polymer concentration near the interface, which greatly modify the fluid viscosity in the region where electroosmosis takes place. A satisfactory mathematical model is derived for the electroosmotic mobility of solutions that present polymer depletion at the wall. The case of solutions containing polymers that adsorb onto the wall is briefly reviewed, and a preliminary approach is discussed for the limit of strong polymer adsorption. In order to illustrate the theoretical discussions, experimental data obtained from aqueous solutions of carboxymethyl cellulose in fused-silica capillaries are presented. Relevant results are observed, which are appropriately captured by the modelling proposed. The fundamental phenomena discussed in this work are of interest in microfluidics and electrophoresis.

Nonlinear Smoluchowski velocity for electroosmosis of Power‐law fluids over a surface with arbitrary zeta potentials

“…which is the Smoluchowski slip velocity for the electroosmosis of the Power-law fluids under small zeta potentials, and it was already obtained in [19,23].…”

“…Afonso et al [22] presented an analytical solution for the steady-sate viscoelastic fluid flow of the Phan-Thien-Tanner type fluids under the combined influence of pressure and electrokinetic forces. Very recently, Olivares et al [23] and Berli [24] conducted experiments to measure the electroosmotic mobility of a typical polymer solution, and found their experimental results can be well predicted by the theory reported in [19]. Nevertheless, it should be pointed out that all these existing mathematical models assume small zeta potentials.…”

Investigation of the effects of time periodic pressure and potential gradients on viscoelastic fluid flow in circular narrow confinements

“…Recently, the necessity of manipulation of biofluids (for example blood, DNA solutions) and polymeric liquids in small confinements has triggered a renewed interest in the dynamics of nonNewtonian fluid. Berli theoretically studied the utilization of steady PDF (Berli 2010a), steady EOF (Olivares et al 2009;Berli 2010b), and steady combined PDF-EOF (Berli and Olivares 2008) for inelastic non-Newtonian fluids using a power law constitutive equation in both rectangular and cylindrical microchannels. Experiments carried out for steady PDF non-Newtonian flow in a rectangular microchannel inspired by Berli's theory were also reported Abstract In this paper we present an in-depth analysis and analytical solution for time periodic hydrodynamic flow (driven by a time-dependent pressure gradient and electric field) of viscoelastic fluid through cylindrical micro-and nanochannels.…”

Effects of non-Newtonian power law rheology on mass transport of a neutral solute for electro-osmotic flow in a porous microtube

“…solutions 25,26 or biofluids. 27 Various studies involving power law and viscoelastic fluid models are available to characterize the flow behavior 28,29 and heat transfer to quantify the Nusselt number [30][31][32][33] in impervious conduits.…”