Garth Stewart, a 24-year-old Iraq veteran, took his first normal steps since losing part of his leg in the war, thanks to a prosthetic ankle that operates like the real thing. Most foot prostheses work through simple springs, but this new robo-ankle, developed at MIT's Media Lab, has a battery-powered motor, too. When Stewart walks, the energy he exerts is stored in a series of motor-backed springs. Then, when he pushes off with his prosthetic foot, this energy is released, and he moves forward. The motors give this motion more power, and ultimately allow Stewart to expend less energy with each step than he would while wearing a standard prosthetic foot. The robo-ankle also leads to a more natural, fluid gait.
MIT's Hugh Herr, who led the research team, is also an amputee. He tested the invention himself, and compares it to walking on a moving sidewalk in the airport. The device may be commercially available within a year.—Gregory Mone