Effect of Wall Roughness on Electroosmotic Flow in Microchannels

Electroosmotic flow (EOF) is widely used to transport and mix fluids in lab-on-a-chip (LOC) devices. For the parallel-plate microchannel with surface roughness, this paper solved the governing equations using the finite element method (FEM) and the effects of roughness element height and density on the EOF behavior were thus investigated. The simulation results indicate that the strong flow resistance can enhance the pressure reduction and decrease the velocity in microchannels. The average EOF velocity varies linearly with the EDL thickness in smooth channels, which does not vary with the roughness height or interval space or EDL thickness monotonically in homogeneous rough channels. The EOF velocity decreases quickly when the roughness height is very small and slowly after that, and it is influenced most significantly when the roughness interval space is the same as the roughness height.