imagine a window pane repairing its own cracks! No, this is not science fiction. It can actually happen as has been shown recently by a team of scientists, who have developed a plastic which can heal itself when heated and cooled. Plastics that can heal themselves are not new. They have been used in specialised applications for long. Some of them for instance, form polymer chains to bridge over a crack while others release a glue-like substance to close the crack. None of these, however, can be used if the material gets cracked repeatedly.

F Wudl and his colleagues from the Los Angeles-based University of California have developed a plastic that consists of tiny Velcro like strips. The Velcro like links are actually chemical bonds some of which break when the material is heated. When the material is heated to about 120