Unsteady solute dispersion by electrokinetic flow in a polyelectrolyte layer-grafted rectangular microchannel with wall absorption

Tuning Electrokinetic Flow, Ionic Conductance, and Selectivity in a Solid-State Nanopore Modified with a pH-Responsive Polyelectrolyte Brush: A Molecular Theory Approach

“…However, attention should be given to the fact that, because of the lower permitivity value of polyelectrolyte brushes relative to that of water, the PEL permittivity is generally lower than the solution permittivity. A range of 52.8–78 was reported for the relative permittivity of the PEL. , Although the lower limit differs significantly from water permittivity, the upper limit is quite close to it. This is in accordance with the cases for which the grafting density is low, similar to the conditions considered in the present study.…”

“…The body force density vector F is the superposition of the force densities exerted on the ions by the electric field E , given as ρ e E , and the drag force density created by the PE brush. The widely accepted approach for accounting the drag force is to consider a volumetric resistive force proportional to the velocity, which is equivalent to modeling the PEL as a porous medium utilizing the Brinkman equation . Following the earlier models for polymer brushes, such a resistive force is given as ξ PEL U z , where ξ PEL is the drag coefficient of the PEL and equals ξ PEL = μ­[ϕ p ( r )/ l e ] 2 , where ϕ p ( r ) is the monomer volume fraction and l e is the effective monomer size. − It is important to mention that ϕ p ( r ), which is obtained in the previous section by utilizing the molecular theory, varies locally inside the system and is not a fixed value across the brush layer.…”

“…To create a robust flow in micro/nanofluidic devices, the most conventional method uses electroosmotic flow (EOF). − Electroosmosis refers to the flow mobilization of an electrolyte solution in response to an applied electric field through a conduit or channel with charged surfaces. The movement of a fluid in EOF is driven by a redistribution of ions that neutralize electric charges and cause the formation of an electric double layer (EDL). , If the surface is coated with PE chains, it significantly affects the EOF in different ways.…”

“…The movement of a fluid in EOF is driven by a redistribution of ions that neutralize electric charges and cause the formation of an electric double layer (EDL). , If the surface is coated with PE chains, it significantly affects the EOF in different ways. It enhances the flow movement by improving the electric body forces, suppresses the fluid motion when PE brushes possess high drag coefficients, changes the direction of the flow, and even provides a precise control over the flow rate …”

Steric and Slippage Effects on Mass Transport by Using an Oscillatory Electroosmotic Flow of Power-Law Fluids

“…Hydrodynamics and dispersion phenomena of EOF were addressed in the context of non-Newtonian fluids [ 24 , 25 , 26 ]. For instance, recently, the unsteady solute dispersion by electrokinetic flow was studied [ 27 ] by considering wall absorption. Besides, some studies were conducted on the hydrodynamics of the OEOF for non-Newtonian fluids [ 28 , 29 , 30 ], and, recently, the mass transfer of an electroneutral solute in a concentric-annulus microchannel driven by an OEOF for a fluid whose behavior follows the Maxwell model was reported by Peralta et al [ 31 ].…”