Number 66 (Story #2), February 3, 1992 by Phillip F. Schewe and Ben Stein INTELLIGENT MATERIALS are to physical structures (bridges, airplanes, buildings, machines, etc.) what the immune system and the nervous system are to the human body: they serve as embedded sensors of temperature, strain, corrosion, electric current, and a host of other chemical and physical indicators. Piezoelectric ceramics, for example, can turn electrical signals into mechanical strain, or vice versa. This ability might sense fatigue in a bridge support or an airplane wing, and give warning. Electro-rheological fluids transform from a liquid to a solid when heated, and back again when cooled. Shape-memory alloys can be easily moulded at lower temperatures, but return to an orignal shape when heated above a critical temperature. Intelligent materials now have their own journals, scientific meetings, and specialized institutions at places like the Univeristy of Strathclyde (Scotland), Virginia Polytechnic, Michigan State, and Toronto. (Science, 17 Jan. 1992.)