The essential property of insoluble bilayers is that they optimise their area at fixed surfactant number.
Pierre-Gilles de Gennes
What do we mean by soft matter? Americans prefer to call it 'complex fluids.' This is a rather ugly name, which tends to discourage the young students.
Benjamin Franklin performed a beautiful experiment using surfactants: on a pond at Clapham Common, he poured a small amount of oleic acid, a natural surfactant which tends to form a dense film at the water-air interface.
Usually a fiber, after being dipped in a liquid, shows a string of droplets, and thus, for some time, people thought that most common fibers were non-wettable.
I have emphasized experiments more than theory. Of course, we need some theory when thinking of soft matter.
Surfactants allow us to protect a water surface and to generate these beautiful soap bubbles, which are the delight of our children.
