Passive mixing in microchannels by applying geometric variations

Passive mixing by applying geometric variations were studied in this research. In respect to the nature of laminar flow in a microchannel, the geometric variations were designed to try to improve the lateral convection. By doing this, the dispersion of solute was not only contributed by diffusion, but also, and more importantly, the convection in the lateral direction. Geometric parameters versus the mixing performance were investigated systematically in T-type channels, by applying a known computational fluidic dynamic (CFD) solver for microfluidics. Various obstacle shapes, sizes and layouts were studied. As the ratio of the height of obstacles to the depth of channel became negative, it was the special case that obstacles became grooves. The mechanism for obstacles to enhance mixing was to create convective effects. However, the asymmetric arrangement of grooves applied a different mechanism to enhance mixing by create helical shaped recirculation of fluids. The stretching and folding of fluids of this mixing mechanism provided a efficient way to reduce the diffusion path in microchannels. The mixing performance of mixers with obstacles were evaluated by mass fraction, and mixers with grooved surfaces were evaluated by particle tracing techniques. The results illustrated that both of the strategies provided potential solutions to microfluidic mixing.