Thursday, November 8, 2007 - 1:43 PM
569b

Multidimensional Isotachophoretic Focusing in Microfluidic Channels

John S. Paschkewitz, Joshua I. Molho, Hui Xu, Rajiv Bharadwaj, and C. Charles Park. Caliper Life Sciences, 605 Fairchild Drive, Mountain View, CA 94043

Isotachophoresis (ITP) is a powerful electrophoretic technique for sample concentration and separation; when used on microfluidic chips it may be necessary to use serpentine passages or expansion sections to meet design requirements. We have observed novel two-dimensional focusing effects in these geometries. Using a simple analytical model for the behavior in a turn, we illustrate that the focusing effect occurs because the spatial distortion of the leading buffer-trailing buffer interface generates a wall-normal electric field. Using this analytical model we identify the controlling non-dimensional parameters. We present the results of a computational parametric study of this focusing behavior in turns as well as a comparison to experimental visualizations. Finally, we present preliminary computational results for ITP in expansions.