There's a lot of grim news out there today, so here's a bit of the feel-good variety from the weekend: Zac Vawter, 31, climbed 103 floors of Chicago's Willis Tower using a prosthetic leg that he controls with his brain.

Vawter achieved the feat at part of "SkyRise Chicago," a charity climb put on by the Rehabilitation Institute of Chicago. Vawter was aiming to finish the climb in an hour, but he ended up finishing in just 45 minutes, the AP reports.

It was a triumph of will and science. The MIT Technology Review explains how the experimental leg worked:

"The ten-pound artificial leg is being developed by a team led by Levi Hargrove from at the Center for Bionic medicine at the Rehabilitation Institute of Chicago."Nerves from Vawter's amputated leg were re-attached to his hamstring in an early operation. It's those nerves that controlled the mechanical bits on his leg. 'Targeted muscle reinnervation,' a technique Hargrove has described as 'rewiring the patient,' is what allows the prosthetic to function as it does. Electrodes on Vawter's thigh translate the neuron signals to electrical instructions that move the leg."

Vawter will now leave the leg behind. The technology won't be ready for the public for at least a few years.

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