"Bionic" man climbs 103 flights

Zac Vawter, fitted with an experimental "bionic" leg, is silhouetted on the Ledge at the Willis Tower in Chicago, Oct. 25, 2012. After losing his right leg in a motorcycle accident, the 31-year-old software engineer signed up to become a research subject, helping test a trailblazing prosthetic leg that's controlled by his thoughts. Vawter became the first person to stair climb to the 103rd floor of Willis Tower on Nov. 4, 2012.

In this Oct. 25, 2012 photo, Zac Vawter practices walking with an experimental "bionic" leg at the Rehabilitation Institute of Chicago.

In this Oct. 25, 2012, photo, biomedical engineer Annie Simon, left, and research prosthetist Elizabeth Halsne fit an experimental "bionic" prosthetic leg on Zac Vawter at the Rehabilitation Institute of Chicago.

In this Oct. 25, 2012, photo, Zac Vawter kicks a soccer ball with an experimental "bionic" leg as biomedical student Aaron Young makes adjustments to the leg at the Rehabilitation Institute of Chicago.

In this Oct. 25, 2012, photo, Dr. Levi Hargrove, lead researcher for the Rehabilitation Institute of Chicago's Center for Bionic Medicine, holds an experimental "bionic" prosthetic leg at the institute.

In this Oct. 25, 2012, photo, Suzanne Finucane, a physical therapist assistant, right, and prothetist Robert Lipschutz, top, attach electrodes to Zac Vawter's leg as he is fitted with an experimental "bionic" leg at the Rehabilitation Institute of Chicago.

In this Oct. 25, 2012, photo, physical therapist assistant Suzanne Finucane, right, helps Zac Vawter as he practices walking with an experimental "bionic" leg at the Rehabilitation Institute of Chicago.

In this Oct. 25, 2012, photo, Zac Vawter, fitted with an experimental "bionic" leg, looks down from the Ledge at the Willis Tower in Chicago.

Zac Vawter's stands on his bionic leg after he arriving on the 103rd floor of Willis Tower, becoming the first person ever to complete the task wearing the mind-controlled prosthetic limb, Nov. 4, 2012, in Chicago.

Zac Vawter arrives on the 103rd floor of Willis Tower, becoming the first person ever to complete the task wearing a mind-controlled prosthetic limb, Nov. 4, 2012, in Chicago.

Zac Vawter, wearing his bionic leg, stands in the center of a group of researchers from the Rehabilitation Institute of Chicago at Willis Tower in Chicago, Nov. 4, 2012.