Enhancement of mixing performance of water solutions in a micro-mixer with immiscible ferrofluid

The purpose of this study is to develop a novel semi-active micro-mixer. The developed mixer has neither obstacles in microchannels or external electrical power sources outside the microchannel. However, an oil-base ferro-nanofluid is employed to segment two aqueous solutions into droplets when two aqueous solutions interact with the oil-based ferro-nanofluid at a dragonfly shape junction. The mixing between two aqueous solutions in the droplet can be significantly enhanced when the ferro-nanofluid carrying the droplets flow through a permanent magnet outside the microchannel. It is due to the reason that boundaries between the droplets and the oil-based ferro-nanofluid are distorted when the carrier ferro-nanofluid moves into and out of the magnetic field exerted by the permanent magnet. Since no external electrical power is required in the developed micromixer for enhancing the mixing between two aqueous solutions. This type of micro-mixer is called a ldquoSemi-Active Micromixerrdquo.