The temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids is used to establish a one-step method of making three- and four-phase complex emulsions with highly controllable morphologies that can be alternated between encapsulated and Janus configurations by varying the balance of interfacial tensions. Emulsions are of critical importance for research and for applications in the medical sciences, food industry and elsewhere. This paper describes a one-step method that exploits the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids to make three- and four-phase complex emulsions with highly controllable morphologies. The geometry of the emulsions can be accurately tuned between encapsulated and Janus configurations by varying the balance of interfacial tensions controlled through mixtures of surfactant or by stimuli such as light or pH. The ability to reversibly 'present' and 'hide' specific liquid–liquid interfaces within the droplet and tune the droplet morphology offers interesting practical possibilities. Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including Janus droplets (that is, droplets with faces of differing chemistries) and multiple emulsions, are of increasing importance1 in pharmaceuticals and medical diagnostics2, in the fabrication of microparticles and capsules3,4,5 for food6, in chemical separations7, in cosmetics8, and in dynamic optics9. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets’ physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes10, to small-volume but more precise microfluidic methods11,12. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have great utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with controllably reconfigurable morphologies and the potential to create a wide range of responsive materials.

Comparing apples and oranges: A chemoresistive sensor for ethylene can be obtained simply by mixing copper complex 1 with single-walled carbon nanotubes. The resulting devices show sub-ppm sensitivity and high selectivity towards ethylene. The utility of the sensor was demonstrated by following ripening stages in different fruits.