A Singularity inside a Singularity; Splitting a water drop during pinch-off of an oil drop. When a fluid droplet breaks-off from a thinning fluid thread, the thickness of the fluid neck becomes vanishingly small at the point of snap-off leading to a singularity. The snap-off mechanism is driven by surface tension forces - surface tension reduces the surface area by decreasing the thickness of the fluid thread.
We add surfactants to the aqueous dispersed phase to generate ultra-low surface tension inner drops that are encapsulated inside of oil drops with a microfluidic device. As the outer oil drop pinches off, due to the Plateau-Rayleigh instability, a trapped water drop inside the oil neck deforms and stretches before splitting into two. (Gif and emulsion credits: L. L. A. Adams)














