Dynamic superconcentration at critical-point double-layer gates of conducting nanoporous granules due to asymmetric tangential fluxes |
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| Authors: | Shau-Chun Wang Hsien-Hung Wei Hsiao-Ping Chen Min-Hsuan Tsai Chun-Ching Yu and Hsueh-Chia Chang |
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| Institution: | 1Department of Chemistry and Biochemistry, National Chung Cheng University, Chia-Yi 621, Taiwan;2Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan;3Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA |
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| Abstract: | A transient 106-fold concentration of double-layer counterions by a high-intensity electric field is demonstrated at the exit pole of a millimeter-sized conducting nanoporous granule that permits ion permeation. The phenomenon is attributed to a unique counterion screening dynamics that transforms half of the surface field into a converging one toward the ejecting pole. The resulting surface conduction flux then funnels a large upstream electro-osmotic convective counterion flux into the injecting hemisphere toward the zero-dimensional gate of the ejecting hemisphere to produce the superconcentration. As the concentrated counterion is ejected into the electroneutral bulk electrolyte, it attracts co-ions and produce a corresponding concentration of the co-ions. This mechanism is also shown to trap and concentrate co-ion microcolloids of micron sizes too (macroions) and hence has potential application in bead-based molecular assays. |
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