The mixing performance of five novel micromixers was assessed using the Villermaux–Dushman protocol. Mixing in passive mixers may be desired at a low or high Reynolds number (Re) depending on the configuration of the mixer's performance. This study is aimed at comparing the mixing performances of backward arrow-, loop-wave-, square-wave-, circular-wave-, and box-wave-shaped micromixers with a back arrow-shaped inlet using the Villermaux–Dushman protocol at Re > 50. A mixing performance test was performed at flowrates ranging from 1000 to 50 mL h-1. Based on the UV absorbance values and mixing times of mixed fluids from the five micromixers, the order of mixing performance at Re > 50 was as follows: square-wave- > circular-Wave- > box-wave- > loop-wave- > backward arrow-shaped micromixers. This was because of the repeated perturbations of the fluid flow, which was identified in the square-wave with a 90 degrees angle in the sinusoidal direction compared to the loop-wave, which had no angle but was characterized by a crest and trough with repeated perturbation. Also, the split and recombination effect that was present in the circular and box-wave contributed to the better mixing performance than that of the loop and backward arrow shape.
As the Re increased from 50 to 700, the order of performance based on absorbance and experimental mixing times became more consistent and increased progressively from the square-wave to the back arrow shape. A comparison of the mixing efficiency of the five micromixers based on the predicted mixing time also gave a consistent order of performance at all Re values above 100. At an Re of 50 to 100, the mixing performance of the circular and box-wave changed drastically from the initial performance, and this was identified as the aging which occurred in the mixer due to the shape and configuration of the channel.
This design is deemed suitable owing to its enhanced mixing efficiency and simpler manufacturing process, particularly when compared to existing models that are employed in biomedical and biochemical analyses.
