Markus Buehler of the Massachusetts Institute of Technology and editor of the Impact section of MRS Bulletin, publishing new research, interviews Esther Amstad of École Polytechnique Fédérale de Lausanne about her group’s work on creating stable emulsions, using novel chemistry, materials, and design principles. Emulsions are used, for example, in food, certain drug and cosmetic formulations, agriculture, and as paints. Key to the successful use of emulsions is a good drop stability. Appropriate surfactants are often selected based, in part, on their hydrophilic-lipophilic balance (HLB), which determines their solubility. Amstad’s group determined how the HLB value of perfluorinated block-copolymer-based surfactants influences the emulsion stability, providing guidelines for an economical, benign, and targeted synthesis of appropriate perfluorinated surfactants that efficiently stabilize water-in-perfluorinated oil emulsions. Amstad demonstrates that water-in-perfluorinated oil drops are most stable if the HLB value of the surfactants is around 2.5. This work is published in MRS Bulletin doi.org/10.155....