In the body, muscular movement results from voluntary and involuntary contractions triggered by impulses from the brain. Zhang gets the same results with a new class of electroactive polymer and a small electrical stimulus. "It's like rope - you can stretch it outor you can roll it up," says Zhangof the new material, pointing to pictures on his lap-top. The curled forms look like uneaten spaghetti noodles left on a dinner plate.

To explain one way in which the polymer moves, Zhang tears two long pieces of Scotch tape, attaches them to his fingertips with the non-stick sides facing each other, then draws his fingers together. Despite his efforts to unite them, the pieces repel each other. The same electrical charge bends a polymer muscle, hesays. The bigger the charge, the more the polymer bends. "The polymer I use to make these rolls has a high dielectric constant," Zhang notes. That means it doesn't require much voltage: a AA battery provides enough to cause a contraction, so powering Zhang's muscles is both inexpensive and safe.Currently, Zhang is working with researchers at the Hershey Medical Center to develop a polymer-based micropump that would allow an artificial heart muscle to pump blood."In theory," he says, "a polymer muscle can replace any muscle in the body."

-Liliana M. Naydan

Qiming Zhang, Ph.D., is professor of electrical engineering, 187 Materials Research Lab, University Park, PA 16802; 814-863-8994; qimingzhang@psu.edu.