Repeat: 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 .
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 .