Inspired by nature, Saarland University researchers have equipped an artificial hand with muscles made from shape-memory wire. The new technology enables the fabrication of flexible and lightweight robot hands for industrial applications and novel prosthetic devices.
The muscle fibers are composed of ultrafine nickel-titanium alloy wires that are able to tense and flex. The material itself has sensory properties, allowing the artificial hand to perform extremely precise movements. The wires have a diameter similar to that of a human hair.
Multiple strands of shape-memory wire connect the finger joints and act as flexor muscles on the front-side of the finger, and as extensor muscles on the rear. In order to facilitate rapid movements, the engineers copied the structure of natural human muscles by grouping the very fine wires into bundles.
"The bundle can rapidly contract and relax while exerting a high tensile force," said Filomena Simone, an engineer who is working on the prototype of the artificial hand as part of her doctoral research.
Unlike a single thick wire, a bundle of very fine wires can undergo rapid contractions and extensions equivalent to those observed in human muscles.
To enable the precise hand and finer movements, a semiconductor chip controls the relative motions of the SMA wires. The controller unit interprets electric resistance measurement data so that the exact position of the wires can be determined at any one time.
The researchers will continue developing the prototype and improve the way in which it simulates the human hand.
