Magnetic antibubbles: Formation and control of magnetic macroemulsions for fluid transport applications

We report the first instance of so called magnetic antibubbles wherein the internal phase comprises an aqueous dispersion of iron oxide (Fe3O4) microparticles, and is thus capable of external control in the presence of a magnetic field. Formation of these bubbles is performed by jetting an iron oxide dispersed phase, through a gaseous medium, into a surrounding aqueous phase. At appropriate trajectory and flow rate conditions, a gas layer is entrained between the two liquids, encapsulating the internal, iron oxide core from the surrounding aqueous phase. We demonstrate that the application of a nonuniform magnetic field confers maneuverability to these bubbles, the intensity of which determines whether the Fe3O4 particles move with the antibubble intact or accelerate through the air layer causing its collapse. An externally applied magnetic field proves a sensitive and determinative means of control, and thus we believe that the magnetic antibubble represents a unique candidate for various fluid delivery and transport applications.