CHICAGO — Zac Vawter considers himself a test pilot. After losing his right leg in a motorcycle accident, the 31-year-old software engineer signed up to become a research subject, helping to test a trailblazing prosthetic leg controlled by his thoughts.
He will put this groundbreaking bionic leg to the ultimate test Sunday when he attempts to climb 103 flights of stairs to the top of Chicago's Willis Tower, at 1,450 feet the seventh-tallest freestanding structure in the world.
If all goes well, he will make history with the bionic leg's public debut. His whirring, robotic leg will respond to electrical impulses from muscles in his hamstring. Mr. Vawter will think, "Climb stairs," and the motors, belts and chains in his leg will synchronize the movements of its ankle and knee. Mr. Vawter hopes to make it to the top in an hour, which is longer than it would have taken before his amputation, but less than it would with his normal prosthetic leg — or, as he calls it, his "dumb" leg.
A team of researchers will be cheering him on and noting the smart leg's performance. When Mr. Vawter goes home to Yelm, Wash., where he lives with his wife and two children, the experimental leg will stay behind in Chicago. Researchers will continue to refine its steering. Taking it to the market is still years away.
"Somewhere down the road, it will benefit me and I hope it will benefit a lot of other people as well," Mr. Vawter said about the research at the Rehabilitation Institute of Chicago.
Bionic — or thought-controlled — prosthetic arms have been available for a few years, thanks to pioneering work done at the Rehabilitation Institute. With leg amputees outnumbering people who have lost arms and hands, the Chicago researchers are focusing more on lower limbs. Safety is important. If a bionic hand fails, a person drops a glass of water. If a bionic leg fails, a person falls down stairs.
The Willis Tower climb will be the bionic leg's first test in public, said lead researcher Levi Hargrove of the institute's Center for Bionic Medicine. The climb, called "SkyRise Chicago," is a fundraiser for the institute with about 2,700 people climbing. This is the first time the climb has played a role in the facility's research.
Specialists not involved in the project say the Chicago research is on the leading edge. Most artificial legs are passive. "They're basically fancy wooden legs," said Daniel Ferris of the University of Michigan. Others have motorized or mechanical components but don't respond to the electrical impulses caused by thought.
"This is a step beyond the state of the art," Mr. Ferris said. "If they can achieve it, it's very noteworthy and suggests in the next 10 years or so there will be good commercial devices out there."