Vortex generation in electroosmotic flow passing through sharp corners

A special phenomenon was found when sharp wedges were set in a microchannel where electroosmotic flow occurred, vortices were induced near the wedges when a DC electric field was imposed. The strength of the induced vortices depends on the concentration of electrolytes and the intensity of the electric field. Latex particles are used to aid the flow visualization. Formation of vortices is due to concentration depletion in the microchannel. Furthermore, the vortices are used to enhance mixing in a micromixer. Experimental results showed that the vortex structures created within the mixing section increase the mixing index from a value of 3% in the upstream region of the microchannel to 78% at the outlet of the mixing section.