Fingers flicking through the air, T. Scott Saponas is rocking a solo in the video game Guitar Hero--without a guitar. A soft band around his forearm monitors the muscles moving his fingers and hand. The band hides a ring of six electrodes that pick up the weak electrical signals produced by active muscle tissue. The signals are relayed to a computer, which in turn controls the game.

Most previous work on muscle interfaces has focused on controlling broad movements of prosthetic limbs by detecting the activity of individual muscles. To recognize more detailed gestures, Saponas developed software capable of processing the jumble of signals from the mass of muscles in the arm. The system has potential for more than just video games. A jogger using Saponas's armband could tense his or her hand muscles to switch tracks on an MP3 player without breaking stride, or a mechanic whose hands were busy inside an engine could use it to control a heads-up display.

Saponas created the software as a graduate student at the University of Washington. Now working at Microsoft Research, he is interested in combining the muscle interface with other sensors, including accelerometers and gyroscopes, to provide additional precision. --Tom Simonite

Hands free: This armband can translate the complex muscle activity involved in gestures into signals that control electronic devices. (1) Muscles involved in a gesture produce electrical activity. (2) A ring of electrodes detects the activity. (3) Signals are sent to a computer wirelessly.
Credit: Bryan Christie Design