Researchers at Vanderbilt University, working under auspices of Darpa's Revolutionizing Prosthetics 2009 program, are using rocket technology to power a prosthetic arm. Hydrogen peroxide is mixed with a catalyst in a pencil-sized chamber to generate steam, which then powers valves and arm motions through valves connected to spring-loaded joints by monofilament belts. A removable can of hydrogen peroxide in the arm provides power for up to 18 hr. The arm is said to have the same strength and maneuverability as a human arm. In tests, it has lifted about 25 lb, four times more than current commercial prosthetics, and can do it four times faster. And unlike conventional prosthetic arms that have only two joints, the elbow and claw, the prototype includes a wrist that twists and bends, and its fingers and thumb independently open and close. The hottest part of the device are covered with insulating plastic, making them safe to touch. And waste heat in the form of steam passes through a permeable skin producing the equivalent of sweat, which cools the arm.

GRAPHIC: bionicarm.html

CALLOUTS: Forearm catalyst pack
Forearm valve bank
Gas distribution lines
Forearm cylinders
Elbow valve
Elbow catalyst pack
Elbow cylinder
Propellant cartridge