Performance characterization of passive micromixer with dual opposing strips on microchannel walls

• A micromixer can achieve MP of 90% above within a microchannel 15 mm in length.
• MP was reduced at higher flow velocities because the design of the groove features.
• Misalignment between the top and the bottom strip structures reduced MP.
• Alignment between the dual micro features on microchannel walls is critical.

Micromixers are an extremely important component in integrated microfluidic systems; however, achieving uniform mixing in laminar flow with a low Reynolds number can be exceedingly difficult. This study developed a chaotic advection type micromixer using dual opposing strips on microchannel walls, which generated two-layer vortices, enlarged the contact interface, and increased diffusion flux between the mixing liquids, ultimately leading to superior mixing performance. Numerical simulation was employed in the design of the micromixer and a micromilling machine was used in conjunction with PDMS casting for the fabrication of the microfluidic devices. Experiments conducted at flow velocities of 1 mm/s, 5 mm/s, and 10 mm/s produced the following results: (1) 90% mixing performance in a channel length of 15 mm at the three flow velocities, (2) an increase in flow velocity deteriorated the mixing performance because the geometric groove features reverse the mixing performance achieved by previous features, (3) misalignment between the top and bottom micro strips detracted from mixing performance.