A microprocessor-controlled artificial foot can capture part of the energy normally dissipated during walking motion and recycle it to aid walking according to researchers at Delft University and University of Michigan. A conventional prosthesis can increase energy expenditure by 23% over healthy walking, but this new device can reduce that cost to 14% resulting in a much more natural walking style with much less effort. Energy is captured passively using a spring, then a pair of micromotors controlled by a microprocessor releases the energy at the optimum time, then resets the device for the next step. A small battery powers the active components.