Enhancing particle dispersion in a passive planar micromixer using rectangular obstacles

In this paper, we numerically and experimentally examine the effectiveness of conventional fluidic micromixers for the mixing of particle flows and demonstrate that microfluidic mixers designed for efficient fluidic mixing are not necessarily efficient at mixing particles. To enhance particle mixing, particles must be forced to move laterally in microchannels. We accomplish this by introducing obstructions within the microfluidic channel to yield a simple planar passive micromixer design. The micromixer performance was benchmarked against a conventional Y-mixer and the modified Tesla mixer, which has been shown to work well with fluids. Simulations using CFD-ACE+ and experiments using fluorescently labeled 590 nm polystyrene particles show that the obstruction micromixer of this work exhibits excellent mixing performance, achieving ∼90% fluid mixing in 5 mm and ∼90% particle dispersion in 3 mm for Re = 0.05. Overall, the micromixer has a simple planar structure, thus resulting in easy realization and integration with on-chip components in microfluidic lab-on-a-chip (LOC) systems.