The Associated Press reports — 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 that's 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, one of the world's tallest skyscrapers. Read the full story.
Editor's note: These photos were taken on October 25, 2012 and made available to NBC News today.
