Although prosthetic arms have been on the market for some time now, researchers at the Georgia Institute of Technology have come up with one that enables amputees to control their prosthetic fingers individually. This is a major breakthrough, providing users with the fine motor hand gestures that have not yet been achieved by commercially available devices. Jason Barnes, 28, is now able to play the piano for the first time since the amputation of his right arm five years ago.

“Our prosthetic arm is powered by ultrasound signals,” said Gil Weinberg, the Georgia Tech College of Design professor who heads the project. “By using this new technology, the arm can detect which fingers an amputee wants to move, even if they don’t have fingers.”

Most prosthetic arms use electromyogram sensors, which rely on electrodes to pick up electrical signals from the muscles. But according to Weinberg, this set up is not without problems.

“EMG sensors aren’t very accurate,” he says. “They can detect a muscle movement, but the signal is too noisy to infer which finger the person wants to move. We tried to improve the...