An active gyroscopic magnetic micromixer for rapid fluid mixing in droplet based microfluidic systems

We demonstrate a magnetic micromixer designed specifically for rapid active mixing in droplets. The magnetic micromixer is fabricated with composites consisting of magnetite and polydimethylsiloxane (PDMS) using soft lithography techniques. The micromixer spins on the droplet surface and rapidly homogenizes the solution of reagents by actively mixing. The spinning motion also enables the micromixer to balance itself on the curved droplet surface through gyroscopic effect. We have compared the micromixer-assisted mixing to the diffusion based mixing and confirmed the micromixer drastically improved the mixing speed.