Surface conduction and electroosmotic flow around charged dielectric pillar arrays in microchannels

Abstract

Dielectric microstructures have been reported to have negative influences on perm-selective ion transportation because ions do not migrate in areas where the structures are located.However, the structure can promote the transportation if the membrane is confined to a microscopical scale. In such scale where the area to volume ratio is significantly large, the primary driving mechanisms of the ion transportation are transited from electro-convective instability (EOI) to surface conduction (SC) and electroosmotic flow (EOF). Here we provide rigorous evidence on how SC and EOF around the dielectric microstructures can accelerate the ion transportation by multi-physics simulations and experimental visualizations. The microstructures further polarize the ion distribution by SC and EOF so that ion carriers can travel to the membrane more efficiently. Furthermore, we verified, for the first time, that the arrangements of microstructures have a critical impact on the ion transportation. While convective flows are isolated in crystal pillar configuration, the flows show elongated pattern and create an additional path for ion current in the aligned pillar configuration. Therefore, the fundamental findings of the electrokinetic effects on the dielectric microstructures suggest an innovative application in an energy-efficient micro/nanofluidic devices.

Investigation on the Stability of Random Vortices in an Ion Concentration Polarization Layer with Imposed Normal Fluid Flow

“…According to previous literatures, three basic mechanisms for over-limiting regime in ion concentration polarization phenomenon are surface conduction, convection by electro-osmotic flow and electro-osmotic instability [41][42][43][44]. The marginal map obtained here would provide the range of experimental conditions for suppressing the instability among the three basic mechanisms.…”

Eco friendly nanofluidic platforms using biodegradable nanoporous materials

“…In over-limiting region, current value increased as the voltage increased shown in the Fig. 3b because of various electrokinetic mechanisms such as surface conduction [85][86][87][88] , electroosmotic convection 61,89 and electroosmotic instability 81,90 . These I-V characteristics are the fingerprint that the nail plate is a perm-selective material.…”

Dynamic analysis of the extended space charge layer using chronopotentiometric measurements

“…Potassium chloride 1 mM solution were used for the experimentation. For tracking the electrokinetic flows and visualizing the ion concentration profile around the ion concentration polarization (ICP) layer, the negatively charged particle (d = 0.2 μm, Invitrogen) and the fluorescent dye (Alexa488, Sigma Aldrich) were mixed in the prepared solution [33,37,48].…”

“…These zones were called the ion depletion zone and the ion enrichment zone, respectively. In order to characterize these zone, numerous theories and experimentations had been conducted such as the possible overlimiting conductance (OLC) mechanisms by instabilities [26][27][28][29][30][31][32], diffusioosmosis [33], electro-osmotic flow (EOF) and surface conduction (SC) [34][35][36][37][38], etc. Most of these studies pointed that all these nonlinear electrokinetic phenomena were stemming from the development of extended space charge (ESC) layer in front of the electrical double layer (EDL) at an overlimiting current regime, predicted by Rubinstein and Zaltzman [39,40].…”