On Sunday, amputee Zac Vawter climbed 103 stories of the Willis Tower, the tallest building in the Western hemisphere, using a prosthetic limb he controlled with his thoughts.
Many prosthetics work using myoelectric devices, where the limb, such as this bionic hand, moves in response to muscle contractions. But since each muscle contraction can control only one motion, the range of motions is limited. To get more nuanced control of prosthetic limbs, the Rehabilitation Institute of Chicago, which sponsored the indoor climb-a-thon Vawter took part in and outfitted him with the leg, is working on developing thought-controlled prosthetics. To make the leg work, nerves from Vawter’s hamstring were wired to the prosthetic, which was designed by Michael Goldfarb at Vanderbilt University.
A monkey controls his robotic arm with a brain-machine interface.
If this monkey can eat marshmallows with his robotic arm, mind-controlled prosthetics for humans can’t be far off, right? Well, that’s true if all you ever wanted to do with your prosthetic was sit strapped in a chair reaching for marshmallows. But as Michael Chorost explains in a recent feature for Wired, challenges abound when building an arm that works in everyday life.
Over the course of a day, you might use your arm to pick up a chair, unzip your jacket, or scratch your neck—each one of these actions are unique. But statistical algorithms used now can translate the firing of neurons into only a few stereotyped motions. And it’s not just about writing better algorithms; it’s an input problem too. Getting electrodes to pick up signals from the same neurons over time is a continuous battle against the body’s natural defenses: