Leakproof Microcapsules: Encapsulated Air in Colloidal Shells Remain Stable for Over 10 Years

More than 10 years ago, we generated double emulsions with glass capillary microfluidic devices. These double emulsions, drops nested inside drops, are air bubbles encapsulated inside colloidal shells. The shell is leak-proof even under ultrahigh vacuum conditions and ultrahigh and ultralow temperatures. We demonstrate the "leakproofness" of the shell by placing a 2D array of armored bubbles in an ultrahigh vacuum chamber and depositing a superconducting material on the surface of the armored bubbles. After the superconducting thin-film deposition, we measure the transition temperature of the superconductor by placing the sample on a dipping probe in a liquid helium dewar and taking resistance vs temperature measurements. Finally, we show the necessary force required to crush the microcapsules in ambient conditions using a tensile tester.