(227e) Electrophoretic Annular Separator with Combined Poiseuille and Electroosmotic Flow

With recent advances in materials science such as two photon polymerization (Pfleging et al., 2008, Bhuian et al., 2007), new potential now exists for customizing the geometrical design of a microfluidic device structure or capillary electrophoresis geometry in addition to the pore structure in nanocomposite gels (Thompson et al., 2012). These devices have many applications including microreactors and electrokinetic separators, but the focus of this contribution is specifically capillary electrophoresis in an annular channel. The contribution focuses on assessing the role of five key parameters, namely ratio of inner to outer radii of the annulus, electrical double layer thickness, inner to outer wall charge ratio, ratio between EOF and hydrodynamic flow, and ratio of convection to diffusion from a modeling point of view. The model combines both pressure driven Poiseuille flow and electroosmotic flow and inputs this flow into the solute equation. By using area-averaging on the solute equation, optimal times of separation are computed and studied.. Three of the five parameters, mentioned above, could be used in order to reduce optimal separation time: wall charge ratio, ratio between EOF and hydrodynamic flow, and ratio between inner to outer radii.  Rectangular channels tended to produce the smallest optimal time of separation, a result which can be explained by comparison of the relative magnitudes of the effective velocity and effective diffusivity in the annulus. The results are not only useful for the capillary model but, also, as  guiding explanations to recent experimental findings in nanocomposite gel material ( Thompson, Dissertation).

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