[Abstract]

The performance of functional materials is governed by their ability to interact with the surrounding environment in a well-defined and controllable manner. Whether it is selectively interacting with a biomolecule or a solute, or responding to pH or temperature, the environment-material interface is essential in determining the performance of materials in various applications. As manifested in multi-layered films and multi-phase emulsion drops, additional material interfaces and compartments provide the means to create composite materials where the surface and the bulk of the material can be independently engineered and controlled. This provides a new perspective in the design and fabrication of novel functional materials.
In this talk, I will begin by exploiting the ability to separately tune the surface and bulk properties of a nanostructured polymer thin film. We propose a new physical concept “zwitter-wettability”, whereby the film readily absorbs water vapor while simultaneously exhibiting hydrophobic character to liquid water. These mechanistic concepts and the quantitative morphological characterizations enabled us to design zwitter-wettable films with significantly enhanced antifog and even frost-resistant behavior.
 In the second part of this talk, I will show how we utilize the precise flow control of multi-phasic fluids in droplet-based microfluidics to prepare novel functional materials that otherwise would have been inaccessible. For instance, we produced triple emulsion drops with an ultra-thin intermediate layer consisting of either hydrogel or fluorocarbon oil to successfully encapsulate a broad range of cargo materials with high loading efficiency. These emulsion drops have been demonstrated to exhibit interesting properties and great technological potential for encapsulation and controlled release of challenging and important active materials such as volatile small molecules and proteins in emulsion-templated microcapsules.