Compound drops, namely drops of liquid containing inclusions of a second phase, are of importance in several industrial fields. One of their key features is the large interface between the different phases: atomizing a two-phase liquid drastically improves the heat and mass transfer between the two phases and with the surrounding air. A usual challenge is to generate compound drops of the appropriate size and composition. This video describes the stretching of a capillary bridge of silicone oil (viscous and hydrophobic) containing a drop of water. As the bridge stretches it turns into a two-phase filament: a non-viscous core coated in a viscous sheath. Eventually, this filament breaks up in several compound droplets. We vary the viscosity ratio between the two phases and show the different possible outcomes of the fragmentation.
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