Analysis of mixing for electroosmotic flow in micro/nano channels with heterogeneous surface potential

Electroosmotic flow in micro and nano channels deals with the low Reynolds number effects due to weak inertial forces. It requires a very long channel for mixing of different species in low Reynolds number through diffusion. The motivation of the present study is to increase the mixing performance when more than one species with heterogeneous surface potential is considered. The generation of vortical flow due to the presence of wall heterogeneity at different locations of the channel is discussed. The flow characteristics for the present study are obtained by numerical solution of the Poisson equation, the Nernst-Planck equation, and the Navier-Stokes equation, simultaneously. A numerical method based on the pressure correction iterative algorithm (SIMPLE) is adopted to compute the flow field and mole fraction of the ions. The potential patch along the channel walls induces a strong recirculation vortex which in turn generate a strong pressure gradient to increase the mixing performance. The streamlines follow a tortuous path near patches.