Numerical and Experimental Investigation of Mixing Enhancement in a Zigzag Passive Micromixer with D-Shaped Obstacles

Micromixers are crucial for rapid and homogeneous mixing in lab-on-a-chip systems. This study presents a novel passive micromixer that synergistically combines a Zigzag channel with D-shaped obstacles to enhance mixing across a broad Reynolds number (Re) range of 0.1-50. The design leverages flow splitting, recombination, and the generation of localized high-velocity streams to effectively disrupt laminar flow. A comprehensive parametric study optimized key geometric parameters, including obstacle dimensions (b₂, a₂) and the number of mixing units (n). Results show that optimizing b₂ to 500 μm and increasing a₂ to 250 μm significantly enhances mixing efficiency. Mechanistic analysis reveals that centrifugal forces in the Zigzag channel work synergistically with obstacle-induced perturbations to stretch and fold the fluid interface, promoting transverse transport. The optimized mixer, fabricated and experimentally validated, achieves a high mixing index (>0.85) under all Re conditions. This work provides valuable design insights for developing efficient, compact micromixers for micro-total analysis systems.