In recent years, there are growing interests in the use of free flow isoelectric focusing (FFIEF). In FFIEF, a thin sheath of laminar flow is introduced perpendicular to the direction of the applied electric field for continuous separation of proteins and charged species. This technique is especially useful in microfluidic device since the electrophoretically separated bands do not have to be mobilized for detection or further analysis. In this study, a mathematical model is developed to simulate free flow isoelectric process in microfluidic devices considering electroneutrality and incompressibility of electrolytes. Our mathematical model is based on mass, momentum and charge conservation equations. A finite volume based numerical scheme is implemented to simulate two dimensional FFIEF in a microfluidic chip. Simulation results indicate that pH gradient forms as samples flow downstream and proteins can be separated effectively using this technique. A new design of microfluidic chip is proposed for separation for cardiac troponin I from serum albumin using FFIEF technique.

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