Ion concentration polarization in a single and open microchannel induced by a surface-patterned perm-selective film

Abstract

We describe a novel and simple mechanism for inducing ion concentration polarization (ICP) using a surface-patterned perm-selective nanoporous film like Nafion in single, open microchannels. Such a surface-patterned Nafion film can rapidly transport only cations from the anodic side to the cathodic side through the nanopore clusters so that it is possible to generate an ICP phenomenon near the Nafion film. In this work, we characterize transport phenomena and distributions of ion concentration under various electric fields near the Nafion film and show that single-channel based ICP (SC-ICP) is affected by Nafion film thicknesses, strengths of applied electric fields, and ionic strengths of buffer solutions. We also emphasize that SC-ICP devices have several advantages over previous dual-channel ICP (DC-ICP) devices: easy and simple fabrication processes, inherently leak-tight, simple experimental setup requiring only one pair of electrodes, stable and robust ICP induced rapidly, and low electrical resistances helping to avoid Joule heating, and membrane perm-selectivity breakdown but allowing as high bulk flow as an open, plain microchannel. As an example of applications, we demonstrate that SC-ICP devices not only have high potential in pre-concentrating proteins in massively parallel microchannels but also enable the concentration and lysis of bacterial cells simultaneously and continuously on a chip; therefore, proteins within the cells are extracted, separated from the concentrated cells and then pre-concentrated at a different location that is closer to the Nafion film. Hence, we believe that the SC-ICP devices have higher possibilities of being easily integrated with traditional microfluidic systems for analytical and biotechnological applications.

Multiphysics Simulation of Ion Concentration Polarization Induced by a Surface-Patterned Nanoporous Membrane in Single Channel Devices

“…23 As the electric potential increases, the preconcentration location gets closer to the membrane. This is mainly because the enhanced EOF from a high electric potential shrinks the diffusion region of ions by suppressing the IDZ.…”

Aptamer-functionalized microtubules for continuous and selective concentration of target analytes

“…Notably, the use of most microfluidic pre-concentration devices requires an additional separation step on a chip to identify the target analytes, which usually requires additional time and labor [7]. In addition, concentrated biomolecules are exposed to relatively harsh environments, because these devices involve spatially steep and temporally rapid environmental changes such as changes in ion concentration (buffer strength) [5,30], electric field [31], non-linear vortex conditions [32], and temperature [2], which appear to be unfavorable for some biological samples.…”

“…However, the large dynamic range of biological samples with highly variable concentrations has been a hurdle for detecting specific target biomarkers (analytes) in a highly sensitive and selective manner [1]. For more than two decades, numerous techniques for amplifying the initial concentrations of biological samples using a variety of microfluidic mechanisms have been reported [2][3][4][5][6]. However, the common weakness of these mechanisms seems to be that all analytes in a biological sample are pre-concentrated together, which makes additional separation techniques necessary to identify specific target analytes from others.…”

An electrokinetic study on tunable 3D nanochannel networks constructed by spatially controlled nanoparticle assembly

“…[1][2][3][4] The electrokinetic properties on this scale have intrigued research applications including chemical mixing, 5,6 energy harvesting, 7-12 biomolecule concentration 13,14 and separation, 15 water desalination and purification, 16 nanofluidic transistors, 17 ionic diodes, 18 etc. Most devices in diverse studies on nanofluidic electrokinetics have similar structures, that is, two microfluidic channels are physically interconnected with nanofluidic channels as a nanojunction.…”

“…Most devices in diverse studies on nanofluidic electrokinetics have similar structures, that is, two microfluidic channels are physically interconnected with nanofluidic channels as a nanojunction. Recently, various nanojunctions are employed such as polymeric ion-exchange membranes (Nafion® 10,13,14,16,19 or Neocepta® [20][21][22] ), porous hydrogel membranes, 23,24 bulk-machined nanochannels in a glass or silicon wafer substrate, 1,[5][6][7]15,[25][26][27][28] and ion track-etched nanopores. 8,9,18,29,30 However, these reported nanojunctions have several disadvantages; in the case of polymeric membranes and porous hydrogels, it is hard to control the geometries, for example, the pore size, its shape, and the location in the microfluidic channels.…”