In the Artificial Muscle Research Institute at the University of New Mexico, electricity is in the air. When lab director Mohsen Shahinpoor applies a voltage to an artificial "hand" made of a polymer-metal composite, its fingers curl into a fist. Poke around the lab and you'll see robotic fish swimming, wings flapping, and arms lifting-all gaining their muscle from electrically activated polymers. You've seen robots before, but there is something different about these. They look alive.

Since the early 1990s, materials scientists and engineers have been developing electroactive polymers for use as sensors, actuators, and artificial muscles. An applied voltage changes the polymer's composition or molecular structure so that it expands, contracts, or bends. The motion is smoother and more lifelike than movement generated by mechanical devices: like muscles, polymers are flexible, unhampered by the clunky rigidity of gears and bearings. Scientists believe that with this similarity to natural motion, electroactive polymers could revolutionize robotics and biomedical devices. Such materials could make it possible to design robots that maneuver with the grace of a human, prosthetic legs that move and feel real, and implantable microdelivery systems that smoothly and quietly pump drugs to where they're needed.