(144e) Stable Polymer- and Nanoparticle-Shelled Bubbles

A bubble is a globular body of gas dispersed in a liquid. Monodisperse and stable bubbles have potential applications in the fabrication of functional lightweight materials with hierarchical structure and in the encapsulation of flavors and fragrances for food and cosmetics additives. They also can be used in contrast-enhanced ultrasonography and drug delivery applications. It is, however, challenging to make gas bubbles with high uniformity in size and properties due to the stochastic nature of traditional bubble generation methods, which rely on shearing gas in water. It is also difficult to store bubbles without significant physical changes for an extended period of time due to the Laplace pressure across air-water interface. Here, we introduce a microfluidic approach to generate monodisperse and stable bubbles by employing a monodisperse air-in-oil-in-water (A/O/W) compound bubble. The oil phase comprises a volatile organic solvent in which hydrophobic materials are suspended or dissolved. Upon the evaporation of the organic solvent, the materials in the oil layer form a stiff shell at the air-water interface. On the basis of this approach, we generate monodisperse bubbles with nanoparticle- and polymer-shells, showing drastically enhanced stability of the bubbles against dissolution and coalescence. We show that the ratio of the thickness of bubble shell to bubble radius is critical in generating un-deformed bubbles from A/O/W compound bubbles. Multicomponent bubbles are also produced by incorporating a variety of materials into the nanoparticle shell. We demonstrate the versatility of this approach in generating multicomponent bubbles by creating fluorescent and magnetic bubbles.