Efficient micromixing using induced-charge electroosmosis

Lab-on-a-chip (LOC) devices which utilize electrokinetics for fluid transport are invariably poor mixers due to the nature of low-Reynolds-number flows. For many such devices, efficient mixing is needed for fast analysis, but the predominant mechanism of equalizing concentration differences is often diffusion-a relatively slow form of mass transfer. In this numerical study, we propose a novel micromixer design which utilizes the recent concept of induced-charge electroosmosis for enhancing fluid mixing. As validation, it is shown that numerical simulations of fluid flow in the proposed system are in good agreement with analytical solutions available for electrokinetic flow and electrokinetic mixing in traditional microchannels. The conventional mixing performance index is modified so that it accounts for the length required for desired mixing as well as the concentration gradients across the channel width. With the help of the modified mixing index, the proposed mixer is compared with the traditional mixer design and found to be superior in performance. Furthermore, the effects of design parameters on mixing performance are analyzed for possible device implementation.