Stroke victims and other people suffering from "drop foot"-a condition in which the front of the foot can't be controlled-generally wear stiff braces to keep their afflicted feet from flopping and dragging when they walk. But a device under development could give them a robotic boost for improved mobility. Instructor Hugh Herr and graduate student Joaquin Blaya of a joint MIT-Harvard program in health technology, together with electrical engineer Gill Pratt of Olin College in Needham, MA, built an ankle brace with a motor that raises and lowers the front of the foot as the heel strikes the ground and lifts again, providing more natural movement and a reduced risk of falling. The battery-powered device, developed at MIT's Artificial Intelligence Laboratory, uses algorithms modeled on "biological information about how a normal ankle is controlled," Herr says. The first tests of the contraption on real patients are expected to begin late this year.