Numerical simulation of electroosmotic flow.

We have developed a numerical scheme to simulate electroosmotic flows in complicated geometries. We studied the electroosmotic injection characteristics of a cross-channel device for capillary electrophoresis. We found that the desired rectangular shape of the sample plug at the intersection of the cross-channel can be obtained when the injection is carried out at high electric field intensities. The shape of the sample plug can also be controlled by applying an electric potential or a pressure at the side reservoirs. Flow induced from the side channels into the injection channel squeezes the streamlines at the intersection, thus giving a less distorted sample plug. Results of our simulations agree qualitatively with experimental observations.