Colored particle tracking method for mixing anlysis of chaotic micromixers

Micromixers have a variety of applications in chemical and biological processes, becoming an important component in microfluidic systems. The present work aims at understanding detailed mixing behaviour of micromixers by developing a numerical analysis scheme, which ultimately facilitates efficient micromixer design. A systematic numerical method has been developed, enabling visualization of detailed mixing patterns and quantification of the mixing performance in chaotic micromixers. The overall numerical scheme is named 'colored particle tracking method' (CPTM), consisting of three steps: (i) a flow analysis to obtain a periodic velocity field of a periodic mixing protocol by the Galerkin/least-squares (GLS) method; (ii) a particle tracking step, particles being labeled by a specific color at the inlet according to fluid species, to obtain a distribution of colored particles at the end of the final period; (iii) a quantification of the degree of mixing from the obtained particle distribution. For the last step we propose a new mixing measure based on the information entropy. The CPTM has successfully been applied to three examples of micromixers with patterned grooves to evaluate their mixing performance both qualitatively and quantitatively. The CPTM seems promising as a practically attractive numerical scheme for mixing analysis of chaotic micromixers.