An artificial foot that recycles energy otherwise wasted in between steps could make it easier for amputees to walk, its developers say.

"For amputees, what they experience when they're trying to walk normally is what I would experience if I were carrying an extra 30 pounds," said Art Kuo, professor in the University of Michigan departments of Biomedical Engineering and Mechanical Engineering.

A paper about the device is published in the Feb. 17 edition of in the journal PLoS ONE. The foot was created by Kuo and Steve Collins, who was then a U-M graduate student. Now Collins is an associate research fellow at Delft University of Technology in the Netherlands.

The human walking gait naturally wastes energy as each foot collides with the ground in between steps.

A typical prosthesis doesn't reproduce the force a living ankle exerts to push off of the ground. As a result, test subjects spent 23 percent more energy walking with a conventional prosthetic foot, compared with walking naturally. To test how stepping with their device compared with normal walking, the engineers conducted their experiments with non-amputees wearing a rigid boot and prosthetic simulator.

In their energy-recycling foot, the engineers put the wasted walking energy to work enhancing the power of ankle push-off. The foot naturally captures the dissipated energy. A microcontroller tells the foot to return the energy to the system at precisely the right time.

"Developers say that an artificial foot that recycles energy otherwise wasted in between steps could make it easier for amputees to walk. (Credit: Image courtesy of University of Michigan)"

Source: University of Michigan