Oil and water can for the first time be mixed and separated on demand thanks to a new, reversible surfactant.
The liquid molecule can be switched on or off to mix or separate oil and water. On the one end of this molecule is the hydrophobic part that binds to oily substance and on the other end a hydrophilic part that binds to water.
Bubble carbon dioxide through a solution and the surfactant switches on, leading the oil-and-water mix to form an emulsion. To switch it off again, you bubble air through it, and the oil and water separate again. [Philip Jessop]