video: Three ferrromagnetic liquid droplets containing iron oxide nanoparticle dispersions were shaped into cylinders using a microfluidic device, and then locked in shape by the formation of magnetic nanoparticle surfactants at the interface. The cylindrical droplets were placed in an oil having the same density, so they are buoyant, and then placed on a stirring plate with a spinning bar magnet. Once magnetized, they behave like floating solid magnets, spinning and dancing with each other, and form a stable hydrodynamic pattern, resulting from the balance between vortex-vortex repulsion and magnetic attraction to the center of the magnet rotating underneath. A small drop of a dye solution (Nile Red) was added to the oil to track the flow field around the rotating ferromagnetic liquid droplets. The video is recorded from top view and played in real time. The volume of the ferromagnetic liquid droplets is 2µL, and the length of the ferromagnetic liquid cylinder is 2 mm. This material relates to a paper that appeared in the 19 July issue of Science, published by AAAS. The paper, by X. Liu at Beijing University of Chemical Technology in Beijing, China, and colleagues was titled, "Reconfigurable ferromagnetic liquid droplets." view more
Credit: Xubo Liu