Materials scientists have long played with "shape memory alloys," metals that shift between one shape and another when heated or cooled to just the right temperature. But so far, real-world applications have been limited, because controlling the alloy's shape with temperature is often difficult and inefficient. Now, researchers have found a way to accomplish the same shape-memory tricks using magnets rather than temperature-an advance that could make possible efficient, less clunky moving parts for machine components in aircraft, automobiles or even robots.

Materials scientists Bob O'Handley of MIT and Kari Ullakko from the Helsinki University of Technology in Finland reasoned that an alloy of nickel, manganese and gallium might respond to a magnetic field with a change of shape. When the researchers expose a sample of the new alloy to a magnetic field about two or three times stronger than that generated by a refrigerator magnet, the material becomes rubbery and expands. When the researchers remove the field, a spring pushing on the alloy causes it to revert to its original shape. By alternating the magnetic field at high speed, the researchers can repeat the cycle several thousand times per minute. "It sort of looks like a heart beating very quickly," says O'Handley.