Design and Optimization of a Passive Micromixer with a Double-layered Structure for Rapid Mixing

Micromixers are microchannel devices that provide effective fluid mixing across a small area and a finite flow path. A micromixer, one of the key elements of a microfluidic system, must achieve the highest mixing with the least pressure drop. This work proposes a passive micromixer with five mixing components and a double-layered structure where the fluid streams are split, twisted perpendicularly, and then recombined to take advantage of fluid laminarity, resulting in greater mixing efficiency at shorter flow distances. The study aims to optimize the proposed design using a numerical inquiry and an efficient method to get a greater mixing index and lower pressure drop. In this work, the Taguchi technique and Grey Relational Analysis are used as the optimization tool. To optimize the performance using the standard L9 orthogonal array, the channel width, the layer depth, the constriction channel width, and the pitch have been chosen as the key parameters. The layer depth is found to be the most important factor in the optimization outcome which is derived from the Grey Relational Grade with the highest Signal-to-Noise ratio. Using Comsol Multiphysics Software, the numerical simulation was run in the 0.1 to 100 Reynolds number range. At higher Reynolds numbers, the optimized micromixer is able to provide a mixing index of 0.97 and a pressure drop of 17 kPa at a total length of 8.7 mm. The outcomes demonstrated that the proposed micromixer is suitable for real-world applications in the chemical and biomedical industries where rapid mixing is required.