CHICAGO - Researchers have come up with new technology that may one day help amputee war veterans: an artificial leg that reads brain signals, and it's already being tested out.

The bionic leg that can read your mind. When Zac Vawter wants to take a step, he thinks it and it happens.

"There's nothing special about it in the sense of what I've had to learn. I can just get up from a chair and walk," said Vawter.

He lost his leg in a motorcycling accident, but his brain is still sending commands to a leg that isn't there. The prosthetic has electrodes to read signals in his thigh, and a computer to process them and a mechanical leg to execute them.

On a monitor is a readout of the signals Vawter's leg is getting from his brain, when he thinks about moving.

Over time, a team of doctors and designers led by Dr. Levi Hargrove taught the computer which signals mean what.

"We can figure out using our pattern recognition if he was trying to move his ankle. So knee, ankle, doesn't matter. We learn the pattern and then we tell the bionic leg how to move," said Dr. Hargrove.

The result?

"With this leg, it's, brings me right back to, basically in terms of interacting with stairs, right back to not having an amputation," said Vawter.

To prove it, Vawter climbed the stairs of one of the tallest buildings in America: the Willis Tower in Chicago.

It is kind of noisy and it's not flawless, but the designers say they are working on improvements, maybe even the ability to run. In three to five years, doctors hope to make these legs available to patients, including over 1,000 amputees from the wars in Iraq and Afghanistan.

"The wounded warriors, they've given so much, and anything we can do to help them, do a little bit better or a lot better, that's what we're trying to do," said Dr. Hargrove.

But for now, the bionic leg is still in the lab, in the test phase.

The U.S. Army is supporting the project with an $8 million grant.