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Analytes Preconcentration and Separation in Nanofluidic Channels

Thomas C. Gamble1, Yi Zhang2, Zhen Yuan3, Alexander Neumann4, Gabriel P. Lopez5, Steven R. J. Brueck6, and Dimiter N. Petsev1. (1) Chemical & Nuclear Engineering, University of New Mexico, 1 University of New Mexico, MSC01 1120, Albuquerque, NM 87131, (2) Department of Chemical & Nuclear Engineering, UNM, 209 Farris Engineering Center, Albuquerque, NM 87131, (3) Department of Chemical Engineering, University of New Mexico, Advanced Materials Laboratory, 1001 University Blvd. SE, Suite 100, Albuquerque, NM 87106, (4) Center for High Technology Materials, UNM, 1313 Goddard SE, Albuquerque, NM 87106, (5) Chemical and Nuclear Engineering, University of New Mexico, Farris Engineering Center MSC01 1120, 1 The University of New Mexico, Albuquerque, NM 87131, (6) University of New Mexico, UNM, 1313 Goddard SE Rm 145, Albuquerque, NM 87106

Controlling the field distribution in fluidic channels allows to controllably manipulating dissolved analytes. Examples include the field gradient methods for focusing and preconcentration of charged molecules. In this study we suggest a method for shaping the electric field in nanofluidic channels that are fabricated on a Si wafer. The method exploits the conductivity of SiO2 that allows precise shaping of the externally applied field in the fluid. We present a theoretical model of this system that is based on Maxwell electrodynamics equations. The model has been experimentally verified by conducting an analyte focusing experiment in Si/SiO2 nanaofluidic channels (see the Figure below). Nanofluidic channels can have dimensions comparable to the electric double layer thickness. We analysed the double layer effect on the transport of electric current, analyte electrophoresis and electroosmotic flow. We have shown that very narrow channels exhibit unique features (e.g., ion selecvtivity) that disappear with increasing the cross-sectional dimension.