Experimental and theoretical investigations of non-Newtonian electro-osmotic driven flow in rectangular microchannels

Abstract

With the development of microfluidics, electro-osmotic (EO) driven flow has gained intense research interest as a result of its unique flow profile and the corresponding benefits in its application in the transportation of sensitive samples. Sensitive samples, such as DNA, are incapable of enduring strong flow shear induced by conventional hydrodynamic driven methods. EO driven flow is thus a niche area. However, even though there are a few research studies focusing on bio-fluidic samples related to EO driven flow, the majority of them are merely theoretical modeling without solid evidence from experiments due to the inherent complex rheological behavior of the bio-fluids. Challenges occur when the EO driven mechanism meets with complex rheology; vital questions such as can the zeta potential still be assumed to be constant when dealing with fluids with complex rheology? and "Does the shear thinning effect enhance electro-osmotic driven flow?" need to be answered. We conducted experiments using current monitoring and microscopy fluorescence methods, and developed a theoretical model by coupling a generalized Smoluchowski approach with the power-law constitutive model. We calculated the zeta potential and compared the experimental results with modeling to answer the questions. The results show a reduction of zeta potential in the presence of PEO aqueous solutions. A constant zeta potential is also indicated by varying the PEO concentration and the electric field strength.The shear thinning effect is also addressed via experimental data and theoretical calculations. The results show a promising enhancement of the EO driven velocity due to the shear thinning effect.

Temperature-gradient-induced massive augmentation of solute dispersion in viscoelastic micro-flows

“…One key factor for the experiments is the inclusion of a non-Newtonian fluid. For this purpose, dilute aqueous polymeric solutions such as polyethylene oxide or polyacrylamide can be mixed with the electrolyte solution and then stirred for 24 h (Huang et al 2016;Mukherjee et al 2017a). In this context, it is important to mention that the polymer concentration should remain in the dilute regime, i.e.…”

Numerical study of electroosmotic slip flow of fractional Oldroyd‐B fluids at high zeta potentials

“…Furthermore, in the analytical and numerical study on electroosmotic flow of viscoelastic fluid, Maxwell fluid model , Oldroyd‐B model , and the Phan–Thien–Tanner fluid model were also extensively considered to describe the rheological behavior of fluids. The experimental study on electroosmotic flow of non‐Newtonian fluids can also be found in .…”

Study of microvascular non-Newtonian blood flow modulated by electroosmosis

“…[15] also used the power-law model to analyse the mixing flow in a contracting-expanding microchannel noting that mixing efficiency is decreased with decreasing rheological flow behaviour index. Huang et al [16] also employed the power-law model to confirm experimentally (via electrical current monitoring and microscopy fluorescence methods) that electroosmotic driven flow is enhanced with shear-thinning behaviour in rectangular microchannels. Jiménez et al [17] used the Maxwell viscoelastic model to simulate the electroflow of ionic solutions in rectangular microchannels with large asymmetric wall zeta potentials, addressing both relaxation time effect and noting that velocity assumes a transient oscillatory trend caused by the competition between viscous, elastic and electroosmotic forces.…”