Mixing of liquids using obstacles in microchannels

In general, the Reynolds number is low in microfluidic channels. This means that the viscous force plays a dominant role. As a result, the flow is most likely to be laminar under normal conditions, especially for liquids. Therefore, diffusion, rather than turbulence affects the mixing. In this work, the commercial computational fluid dynamics tool for microfluidics, known as FlumeCAD, is used to study the mixing of two liquids in a Y channel and the results are presented. To improve mixing, obstacles have been placed in the channel to try to disrupt flow and reduce the lamella width. Ideally, properly designed geometric parameters, such as layout and number of obstacles, improve the mixing performance without sacrificing the pressure drop too much. In addition, various liquid properties, such as viscosity, diffusion constant, are also evaluated for their effect on mixing. The results indicate that layout of the obstacle has more effect on the mixing than the number of the obstacles. Placing obstacles or textures in the microchannels is a novel method for mixing in microfluidic devices, and the results can provide useful information in the design of these devices.