The hand uses similar signal-processing algorithms to other prosthetics on the market.The big advance is that it does not require invasive surgery or electronic implants into the residual limb to communicate with the user's brain.Sensors on the skin record electrical activity from the remaining arm muscles.In an intact arm, this activity would tell those muscles how to operate the hand.Instead, they are interpreted by pattern-recognition software that sends appropriate commands to the pump to move the artificial hand in the same way.Meanwhile, other signals travel in the opposite direction from sensors in the hand's fingertips to nerves in the arm, whence they are relayed to the brain and provide a sensation of touch.The upshot is something which responds like a hand and feels like one to the user.Dr Gu and his colleagues compared the efficacy of their invention with that of existing models using tests borrowed from research into strokes and spinalcord injuries.These included writing, grasping and lifting objects, lifting food to the mouth, and stacking draughtsmen.Normally, they found, it worked better―particularly for delicate tasks like handling fragile objects, petting a cat and shaking hands.The other advantage of Dr Gu's invention is that it is cheap.The components it is made from cost about $500.Existing models may sell for $10,000 or more.
