Dispersion Modeling in Microfluidic Channels for System-level Optimization

Chip-based microfluidic separation systems often use serpentine channels to achieve long separation lengths in minimal area. Such designs suffer from the ‘racetrack’ effect due to the bends in the microchannel. In addition, the skew produced by a bend cannot be undone by an equal and opposite bend due to non-axial diffusion occurring in the inter-turn straight channel. This paper analyzes the non-axial diffusion of skewed bands of solute, in electrokinetic microchannels containing turns, to develop models which can be used for a system-level optimization of such designs. Distortion caused by transition and wall effects in the turn geometry and the inter-turn channel are also analyzed. Finite volume simulations are used to verify the proposed theory.