Obstacle-free planar hybrid micromixer with low pressure drop

Planar micromixers with repetitive units have received substantial research interest since they allow low cost, lab-on-a-chip (LOC), and point-of-care (POC) systems to achieve a proper level of mixing for any given process. This paper presents an efficient planar micromixer that combines four types of mixing units, including convergent-divergent, circular, rhombic, and G-shaped micromixers. Their combinations and resulting effects on the mixing efficiency are numerically and experimentally investigated. A comprehensive Taguchi design of experiment method was used to reduce the number of the combinations from 1024 to only 16, among which a micromixer made of rhombic and G-shaped units readily showed a mixing efficiency beyond 80% over a wide range of inlet Reynolds numbers 0.001-0.3 and 35-65; meanwhile, a pressure drop as low as 12 kPa was reported. The velocity and concentration fields and their gradients within the nominated micromixer were analyzed, providing a better understanding of the mixing mechanism. These results offer design insights for further development of planar micromixers with repetitive unites for low-cost LOC and POC devices.