A numerical computational model of electroosmotic micromixer is developed using a CFD software package, and numerical simulations are executed to verify its accuracy. This rectangular microchannel mixer utilizes heterogeneous surface potential to form recirculation flow and enhance mixing in channel. The basic ζ potential of channel walls is −25mV, and the modulated potentials are +200mV and −200mV, respectively. Several ζ potential modulation modes are studied to optimize the ζ potential modulation, which pattern different modulated ζ potential regions on the top and bottom channel surfaces to produce in-plane vortex. Single-plane (top or bottom) and double-plane (top and bottom) drive vortex are investigated to show their characteristics and influences upon the mixing process. According to the simulation results, a reference entry length indicates that the ratio of entry length to channel width must be greater than one to eliminate the corner effect completely. Mixing process of two kind of modulation arrangements are also compared with the aim of a more effective mixing. In the end an electroosmotic mixer is designed and simulated numerically, which works under a 50000V/m electric field and can get a flowrate about 0.5nL/m with mix length less than one centimeter.

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