New paper in Adv. Mater. Technol.

posted Feb 5, 2018, 5:00 PM by Shin-Hyun Kim   [ updated Feb 5, 2018, 5:38 PM ]
Sangmin Lee, Tae Yong Lee, and Shin-Hyun Kim, "Microfluidic Production of Capsules-in-Capsules for Programmed Release of Multiple Ingredients", Advanced Materials TechnologiesAccepted for publication (2018). (Corresponding author)

Capsules with thin shells have a high loading capacity and are thus well-suited containers for reagents that must be stored in confined volumes. Capsules contained in larger capsules, so-called double capsules, allow the encapsulation of distinct reagents within small, defined, well-separated volumes. Therefore, they offer possibilities to initiate reactions in confined volumes and to release distinct bioactives sequentially while minimizing the risk for cross contaminations. Here, we present a new microfluidic capillary device that enables the assembly of water-oil-water-oil-water (W/O/W/O/W) quadruple-emulsion drops whose oil layers are ultra-thin. These quadruple emulsions can be converted into double capsules with thin membranes through either evaporation-induced consolidation of biodegradable polymers or photopolymerization of monomers. We demonstrate that the membrane composition of the inner and outer capsules can be independently selected to enable programmed release of distinct encapsulants. For example, we employ biodegradable polymers with two different degradation rates as the membrane materials that enable sequential release of two different encapsulants. In addition, the release of the encapsulants can be triggered by external stimuli such as osmotic pressure. This new class of double capsules provides new opportunities for drug delivery and screening assays that require sequential release of multiple water-soluble ingredients.