Enhancing Microfluidic Systems’ Mixing Efficiency Using Design Models with Convergent–Divergent Sinusoidal Microchannel Walls: Experimental Investigations Based on Entropy Minimization Flow Structures

This study presents an innovative passive micromixer design featuring convergent–divergent sinusoidal walls, evaluated using the Villermaux–Dushman protocol. Five distinct designs were fabricated and tested, demonstrating superior mixing efficiency without additional obstructions. Testing of flow rates from 1000 to 50 mL/h revealed that the square-wave micromixer had the highest efficiency due to repeated fluid perturbations from its 90-degree angles. The loop-wave mixer performed the worst due to its lack of angles. The circular and box-wave mixers outperformed the loop-wave and backward arrow mixers due to their split and recombination effects. These designs, especially the circular and box-wave designs, offer optimal mixing for short-length applications, improving the efficiency and manufacturing simplicity for biomedical and biochemical analyses.