ABSTRACT
Emulsions are heterogeneous systems in which one liquid is dispersed in another liquid. The dispersed phase exists as droplets that are kinetically stabilized by an emulsifier. The most common types of emulsions are oil-in-water (O/W) and waterin-oil (W/O). The word “water” and the symbol “W,” when referring to an emulsion, may not necessarily mean pure water but rather an aqueous solution. In most cases, it is an aqueous solution of surfactant that contains micellar aggregates. The aqueous solution may also contain other water-soluble species, such as salt, thickener, and biocide. Similarly, “oil” and the symbol “O” refer to a water-immiscible liquid that is less polar than water. Emulsions can display a more complicated morphology than the simple O/W or W/O. Multiple emulsions such as water-in-oil-in-water (W/O/W) and oil-in-water-in-oil (O/W/O) have been long known. An emulsion may also contain more than two immiscible phases. Janus and Cerberus emulsions, for example, have been well demonstrated in recent years [1,2].
