Someday, folks with artificial hearts might have to take long, daily walks to stay alive -- not because exercise is good for their health, but because those walks literally power their synthetic organ. A team of students from Rice University called "Farmers" are developing a device that can generate energy and feed it back into the body to be used by an artificial heart. Their creation? A modified medical leg brace with a motor attached right on the joint, so it can produce energy every time the user bends his knee. An earlier prototype for the same project -- it's a multi-year endeavor, and the current model is the brainchild of the third batch of students -- could also generate power by walking. However, that wasn't a brace, but a shoe with a pedal attached to the sole.