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.