Optimization of slanted grooved micromixer with a serpentine channel at a lower Reynolds number

Abstract In Lab-On-Chip (LOC) applications, micromixing is the most important step to obtain fast analytical response in many biochemical and biological detections. Design and realization of smaller and shorter mixers with higher efficiency has become a necessity more than a recommendation. In this work, a numerical optimization of a passive mixer with a serpentine-shaped channel is proposed. By considering a laminar flow regime, the continuity and momentum equations, along with the advection-diffusion equation, are solved to evaluate the mixing performance. The optimization of the slanted grooves micromixer with a serpentine channel is achieved using computational fluid dynamics (CFD) and response surface methodology (RSM) based on Box-Behnken design. This method is used to find a second-order polynomial regression model and to obtain the optimal groove design. The considered objective function is the mixing index, while the four design variables are: the number of grooves per half cycle (N), the groove angle ( θ ), the groove depth to channel height ratio (d/h) and the ratio of groove width to channel width ( W d /W ). The optimization results indicate that the highest values of each selected interval of the groove depth to channel height ratio (d/h) and the angle between the radius and the groove ( θ ), on the other hand, the ratio of groove width to channel width ( W d /W ) of about 0.45 are desirable to promote faster mixing. The Flow behaviour in optimized “slanted grooves mixer (SGM) with serpentine channel was tested for low Reynolds number Re ranging between 0.3 and 5, and the results have shown that in the range of Re from 0.3 to 0.7 the mixing index is greater than 85%, for large range of Re from 1 to 4.5, the mixing index reaches the value of 93% in the first cycle of the channel and it approaches 100% for channel length of 1.25 mm from the inlet of the channel. Thus the most important result of this work shows that higher efficiency is obtained for short distance and the required pressure drops decreases. This micromixer can be selected as a good candidate in applications that require a high degree of mixing with relatively small length mixing as polymerase chain reaction (PCR) in the analysis and extraction of DNA.