Chaotic passive micromixers with microstructures placed on the top and bottom floors of channel

The objective of this study is to present chaotic micromixers in which a series of microstructures are placed on the top and bottom floors of channels. Passive micromixers fabricated by MEMS technologies with crosswise grooves and ridges are considered. Numerical simulations using the commercial software CFD-ACE(U) are employed to predict the effects of various patterns of microstructures on mixing efficiency with the range of Reynolds number from 0.05 to 50. The influences of non-dimensional parameters such as the Reynolds number as well as the geometrical parameters on the mixing performance are presented in terms of the mixing index. Micromixers which are made of PDMS are used to investigate the mixing characteristics influenced by the different kinds of microstructures. A significant amount of stirring resulting from chaotic mixing can be seen due to the fluids flowing through the crosswise ridges embedded on the top and bottom floors of channels. While Re is greater than 1, the mixing index of the micromixer with crosswise ridges starts to increase as Re increases. This means that the flow field in this micromixer results in efficient chaotic mixing. Simulation results are presented to compare with the experimental data, and a very good agreement can be achieved. Finally, various numbers of the crosswise ridges with the same orientation in one cycle of the channels are investigated to present to the mixing performance in the microchannels. An optimal design can be found in our works.