What happens when you stir a mixture of soap and water? Soap contains surfactant molecules, which typically have one end - the head - that likes water and a hydrocarbon tail that prefers oil. In a mixture of soap, oil and water the different components compete to satisfy the opposing tendencies of the head and tail groups. And under certain conditions the surfactants self-assemble into long, flexible cylinders, called worm-like micelles.
Scientists have recently become interested in how flow affects these structures, and vice versa. Indeed, it is vital to control the flow of surfactants in many situations, including the production of food, petroleum and household goods, and various applications in medicine. In the 1980s it was found that a thick gel could be formed when a dilute solution of worm-like micelles is stirred, but it could not be explained. Now Sarah Keller, Dave Pine and Joe Zasadzinski at the University of California at Santa Barbara, along with Phillipe Boltenhagen at the Laboratoire d'Ultrasons et de Dynamique des Fluides Complexes (LUDFC) in Strasbourg, France, have studied this gel using electron microscopy and have shown that its structure is quite unlike that of the original micelles (Phys. Rev. Lett. 1998 80 2725).
The full article by Peter Olmsted at the University of Leeds, UK, appears in Physics World magazine (information)