National Geographic : 2010 Jan
5 Residual nerves Electrodes Battery Nerves Spinal cord Wrist rotator There are 17 hand motions. HUMAN ARM 22+ MOVEMENTS From the shoulder to a finger's last joint, an arm has at least 22 points of movement. Nerves carry the brain's instructions from the spinal cord to the muscles. TRADITIONAL PROSTHESIS 3 MOVEMENTS Still the only device available to most amputees, the pincer-hand prosthesis relies on cables moved by pressing levers on a harness with the chin or other arm. PROTO 1 7 MOVEMENTS Nerves that once reached the lower arm are rerouted into other muscles. Electrodes placed on those muscles capture the brain's commands and relay them by wires in the prosthesis. WEIGHT Seven to eight pounds, like the average adult arm. The bionic limb can curl up to 60 pounds. MODULAR DESIGN Placing the controller in the palm will let the prosthesis work for both full and partial amputations. SENSORY DATA Fingertip nodes will detect pressure, vibration, and tem- perature. The data will be sent wirelessly to the electrode arrays, then back through the nerves to the brain. Closing In on a Lifelike Limb HIRAM HENRIQUEZ, NG STAFF; JENNY WANG. ART BY BRYAN CHRISTIE SOURCES: REHABILITATION INSTITUTE OF CHICAGO; JOHNS HOPKINS UNIVERSITY APPLIED PHYSICS LABORATORY; UNIVERSITY OF UTAH THE ABILITIES OF TODAY'S PROTO 1 BIONIC ARM WILL TRIPLE IN THE NEXT PROTOTYPE.