Micromixing of Fluids within Droplets Generated on Centrifugal Microfluidics

Abstract

Experiments were carried out to visualize mixing and reaction of two water-based solutions inside the droplets generated in the microchannels on a rotating disk. The microchannels were composed of a Y-junction to bring the two solutions into contact, a flow-focusing junction to form water-in-oil droplets, and a U-shaped channel to further enhance the droplet mixing. In the centrifugal microfluidics, plug-type droplets of 582-820 μm in length were formed at rotational speeds in the range 400-500 rpm. The mixing efficiency can be highly enhanced to reach as much as 85% for the lower rotational speed where smaller droplets are formed due to lower dispersed-phase flow velocity.