Modelling nanofluidic field amplified sample stacking with inhomogeneous surface charge

Nanofluidic technology has exceptional applications as a platform for biological sample preconcentration, which will allow for an effective electronic detection method of low concentration analytes. One such preconcentration method is field amplified sample stacking, a capillary electrophoresis technique that utilizes large concentration differences to generate high electric field gradients, causing the sample of interest to form a narrow, concentrated band. Field amplified sample stacking has been shown to work well at the microscale, with models and experiments confirming expected behavior [1]. However, nanofluidics allows for further concentration enhancement due to focusing of the sample ions toward the channel center by the electric double layer [2]. We have developed a two-dimensional model that can be used for both micro- and nanofluidics, fully accounting for the electric double layer. This model has been used to investigate even more complex physics such as the role of inhomogeneous surface charge. \\[4pt] [1] Bharadwaj, R., {\&} Santiago, J. G. (2005). \textit{J. of Fluid Mech.}, \textit{543}, 57--92\\[0pt] [2] Sustarich, J. M., Storey, B. D., {\&} Pennathur, S. (2010). \textit{Phys. of Fluids}, \textit{22}(11), 112003