Effects of electric and magnetic fields in magnetic mixing in electroosmotic flows

In this paper, mixing efficiency in electroosmotic flow is numerically simulated at the electric double layer region in the presence of a magnetic field. An incompressible and laminar model is adopted to numerically solve the governing equations involving the magnetic field, electric potential fields, concentration distribution for positive and negative ions (Nernst-Planck), and species concentration. To validate the numerical study, an ideal electroosmotic flow with charged walls is simulated and the results are compared with the analytical solution. For the case with a Reynolds number of 0.02, microchannel length of 40 mu m, the results show that by applying a magnetic field, the mixing efficiency along the microchannel length increases from 60.5% to 79.67%. It is found that the existence of a magnetic field in the electric double layer has a significant impact on pressure distribution along the microchannel wall, however, its effects on the electric fields (internal and external), the distribution of positive and negative ions, and the net electrical charge density are marginal. In addition, the presence of magnetic field creates two relatively large vortices inside the microchannel. The outcomes of the present study will help to improve mixing efficiency in micro-devices with applications in micro-analysis systems and lab-on-a-chip instruments.