Low-dispersion electrokinetic flows for expanded separation channels in microfluidic systems:: Multiple faceted interfaces

A novel methodology to design on-chip conduction channels is presented for expansion of low-dispersion separation channels. Designs are examined using two-dimensional numerical solutions of the Laplace equation with a Monte Carlo technique to model diffusion. The design technique relies on trigonometric relations that apply for ideal electrokinetic flows. Flows are rotated and stretched along the abrupt interface between adjacent regions having differing specific permeability. Multiple interfaces can be placed in series along a channel. The resulting channels can be expanded to extreme widths while minimizing dispersion of injected analyte bands. These channels can provide a long path length for line-of-sight optical absorption measurements. Expanded sections can be reduced to enable point detection at the exit section of the channel. Designed to be shallow, these channels have extreme aspect ratios in the wide section, greatly increasing the surface-to-volume ratio to increase heat removal and decrease unwanted pressure-driven flow. The use of multiple interfaces is demonstrated by considering several three-interface designs. Faceted flow splitters can be constructed to divide channels into any number of exit channels while minimizing dispersion. The resulting manifolds can be used to construct medians for structural support in wide, shallow channels.