Numerical simulation of electroosmotic flow in microchannels with sinusoidal roughness

Electroosmotic flow (EOF) is a promising way for driving and mixing fluids in microfluidics. Aiming at the parallel-plate microchannel with sinusoidal surface roughness, this paper solves the governing equations using the finite element method and the effects of roughness element height and density on the EOF behavior are thus investigated. The simulation results indicate that the bulk flow velocity and the volumetric flow rate decrease slowly with the roughness height when the relative roughness is very small (k < 0.005) or very large (k > 0.05), while decrease quickly when the relative roughness is moderate (0.05 ≥ k ≥ 0.005). The flow rate and the bulk velocity decrease quickly first and then increase slowly with the roughness element density. The volumetric flow rate decreases more quickly than the bulk flow velocity at the same roughness element height or density because of the decreasing of the channel cross area in the presence of the roughness. The results provide valuable insights into the optimal design of microchannel surfaces to achieve accurate flow control in microchips.