Researchers are experimenting with injectible myoelectric sensors (IMES) that detect muscle activity and wirelessly transmit commands to the prosthetic arm. The setup eliminates bulky electrodes glued to the chest. A wire coil wrapped over the shoulder supplies wireless power to the implants and relays signals to computers in the prosthetic that decipher the command and tell the arm to move. The team is also considering implanting electrodes directly on nerves-or in the brain itself-to achieve more natural neural control by 2009.
Researchers are exploring a hydrogen-peroxide pneumatic system to replace electric motors, which are bulky, slow and weak. The hydrogen peroxide reacts with an iridium catalyst to drive the arm's movements. The wearer would install a fresh hydrogen-peroxide canister each morning.
The Proto 2 performs 25 joint motions: The shoulder and wrist are capable of roll, pitch and yaw, the elbow can flex, and the fingers and thumbs bend at each knuckle. Each joint brings together two lightweight "bones" made of carbon fiber and aluminum alloys.
Modular construction-shoulder to elbow, elbow to wrist-allows doctors to adapt the limb to patients' needs.