Zac Vawter put his bionic leg on public display for the first time as he climbed the 103 floors of Chicago's iconic Willis Tower, becoming the first person ever to complete the task wearing a mind-controlled prosthetic limb.
Vawter, who lost his right leg in a motorcycle accident, participated in the annual stair-climbing charity event called "SkyRise Chicago" hosted by the Rehabilitation Institute of Chicago, where he is receiving treatment.
"Everything went great," Vawter said. "The prosthetic leg did its part, and I did my part."
The leg is designed to respond to electrical impulses from muscles in his hamstring. When Vawter thought about climbing the roughly 2,100 stairs, the motors, belts and chains in his leg synchronized the movements of its ankle and knee.
The computerized prosthetic limb weighs about 10 pounds (4.5 kilograms) and holds two motors.
Bionic — or thought-controlled — prosthetic arms have been available for a few years. Knowing leg amputees outnumber people who have lost arms and hands, the Chicago researchers are focusing more on lower limbs. If a bionic hand fails, a person drops a glass of water. If a bionic leg fails, a person falls down stairs.
The stair-climbing event was a research project for us, said Joanne Smith, the Rehabilitation Institute's CEO.
"We were testing the leg under extreme conditions. Very few patients who will use the leg in the future will be using it for this purpose. From that perspective, its performance was beyond measure," Smith added.
Vawter said he prepared on a small escalator at a gym, while researchers spent months adjusting the technical aspects of the leg to ensure that it would respond to his thoughts.
When Vawter goes home, the experimental leg will stay behind in Chicago. Researchers will continue to refine its steering. Taking it to the market is still years away.
The $8 million project is funded by the US Department of Defense and involves Vanderbilt University, the Massachusetts Institute of Technology, the University of Rhode Island and the University of New Brunswick.
"A lot of people say that losing a leg is like losing a loved one," said Vawter. "You go through a grieving process. You establish a new normal in your life and move on. Today was a big event. It's just neat to be a part of the research and be a part of RIC."