Nonspherical double emulsions with multiple distinct cores enveloped by ultrathin shells.

Microfluidics has provided means to control emulsification, enabling the production of highly monodisperse double-emulsion drops; they have served as useful templates for production of microcapsules. To provide new opportunities for double-emulsion templates, here, we report a new design of capillary microfluidic devices that create nonspherical double-emulsion drops with multiple distinct cores covered by ultrathin middle layer. To accomplish this, we parallelize capillary channels, each of which has a biphasic flow in a form of core-sheath stream; this is achieved by preferential wetting of oil to the hydrophobic wall. These core-sheath streams from the parallelized channels are concurrently emulsified into continuous phase, making paired double-emulsion drops composed of multiple cores and very thin middle shell. This microfluidic approach provides high degree of controllability and flexibility on size, shape, number, and composition of double-emulsion drops. Such double-emulsion drops are useful as templates to produce microcapsules with multicompartments which can encapsulate and deliver multiple distinct components, while avoiding their cross-contamination. In addition, nonspherical envelope exerts strong capillary force, leading to preferential coalescence between innermost drops; this is potentially useful for nanoliter-scale reactions and encapsulations of the reaction products.