Modelling the Operational Limits of a Separation Enhancement Method for Capillary Electrophoresis: a Designer's Tool

We report on a model giving new insight into electrokinetic fluid flow in microfluidic devices, and demonstrate its use as a tool for designing capillary electrophoresis (CE) systems; particularly lab-on-a-chip applications. The electroosmotic flow (EOF) is directly related to the zeta-potential which can be dynamically modified by applying a potential to a zeta-potential modification (ZPM) electrode close to the channel wall [1]. We investigate the effect on EOF where the zeta-potential is modified along a single channel wall, rather than complete channel coverage. We consider the effect for a single channel wall because it makes the fabrication process simpler. The EOF affects the amount of separation attainable in CE systems for a given channel length. We show that with control of the EOF, separations can be achieved in channels of shorter length. The use of a single electrode introduces peak broadening; we investigate the effect this has on the separation and the limits it places on the separation enhancement method.