Ion Concentration Polarization by Bifurcated Current Path

Abstract

Ion concentration polarization (ICP) is a fundamental electrokinetic process that occurs near a perm-selective membrane under dc bias. Overall process highly depends on the current transportation mechanisms such as electro-convection, surface conduction and diffusioosmosis and the fundamental characteristics can be significantly altered by external parameters, once the permselectivity was fixed. In this work, a new ICP device with a bifurcated current path as for the enhancement of the surface conduction was fabricated using a polymeric nanoporous material. It was protruded to the middle of a microchannel, while the material was exactly aligned at the interface between two microchannels in a conventional ICP device. Rigorous experiments revealed out that the propagation of ICP layer was initiated from the different locations of the protruded membrane according to the dominant current path which was determined by a bulk electrolyte concentration. Since the enhancement of surface conduction maintained the stability of ICP process, a strong electrokinetic flow associated with the amplified electric field inside ICP layer was significantly suppressed over the protruded membrane even at condensed limit. As a practical example of utilizing the protruded device, we successfully demonstrated a non-destructive micro/nanofluidic preconcentrator of fragile cellular species (i.e. red blood cells).

Non-negligible Water-permeance through Nanoporous Ion Exchange Medium

“…The condition is valid in the cases where the ionic flux induced by the water-permeance is negligible compared to the ionic flux due to the other external stimuli such as concentration difference 4 – 7 and electric field 8 – 10 . For example, an ion concentration polarization phenomenon is triggered by electrically induced counter-ion flux across highly-charged nanoporous medium so that the theoretical model without considering the effect of water-permeance at the interface is enough to elucidate the transport phenomenon adequately 11 – 14 . However, in the case of reverse electrodialysis which is an energy harvesting platform utilizing a salt gradient across the nanoporous medium, diffusioosmotic water-permeance by diffusive flux could be a major transport mechanism 15 – 19 .…”

Controllable pH Manipulations in Micro/Nanofluidic Device Using Nanoscale Electrokinetics

“…Comparing to the initial value, it dropped 84.6% after 2000 s. Otherwise, it slightly dropped from its initial value (31.1% drop). The reason why it slightly dropped in case of pH = 3.5 was that ICP also formed when a micro-and a nano-junction coexist in parallel [55][56][57][58]. While one expects a higher initial current in a micro-micro-micro-connection than one in a micro-nano-micro-connection by considering cross-sectional area, it involves complex interactions such as Donnan concentration of nanoporous material [51,59], surface charge of microchannel [13], the concentration of electrolyte (i.e., Debye length) [2,55], and the transversal dimension of hydrogel itself, etc.…”

Simulation and Experimental Study of Ion Concentration Polarization Induced Electroconvective Vortex and Particle Movement

“…EF Fixed volumetric charge [30] Fixed volumetric charge [31] Fixed surface charge and electric potential [32,33] EF/HF Fixed surface charge [22] Fixed volumetric charge [34] Fixed surface charge and fixed electric potential [35] ICP-2C EF Fixed volumetric charge [31] EF/HF Fixed surface charge This work…”