Wire muscle fibers bring sensitivity to artificial hand

German engineers have created artificial muscles fibers from shape-memory wire that allow an artificial hand to perform precise movements.

Engineers at Saarland University and the Center for Mechatronics and Automation Technology (ZeMA), led by Stefan Seelecke, PhD, a professor of mechatronics at the university, composed the fibers from bundles of ultrafine nickel-titanium alloy wires, allowing the hand to contract and relax.

“Shape-memory alloy (SMA) wires offer significant advantages over other techniques,” Seelecke said in a press release. “Tools fabricated with artificial muscles from SMA wire can do without additional equipment, making them light, flexible and highly adaptable. They operate silently and are relatively cheap to produce. And these wires have the highest energy density of all known drive mechanisms, which enables them to perform powerful movements in restricted spaces.”

Seelecke and colleagues modeled the muscles fibers of the artificial hand on the structure of natural human muscles by grouping the wires into bundles. The wire bundles connect the finger joints and act as flexor and extensor muscles.

Stefan Seelecke

“The bundle[s] can rapidly contract and relax while exerting a high tensile force,” Filomena Simone, an engineer and doctoral student working on the prototype of the artificial hand, said in the release. “The reason for this behavior is the rapid cooling that is possible because lots of individual wires present a greater surface area through which heat can be dissipated. Unlike a single thick wire, a bundle of very fine wires can undergo rapid contractions and extensions equivalent to those observed in human muscles. As a result, we are able to achieve fast and smooth finger movements.”

The wires are controlled by a semiconductor chip, and the system does not require sensors.

“The controller unit is able to interpret electric resistance measurement data so that it knows the exact position of the wires at any one time,” Seelecke said.

The researchers plan to further develop the prototype by modelling hand movement patterns and exploiting the sensor properties of SMA wire, according to the release.

Reference: www.uni-saarland.de/en/home.html.

Filomena Simone, an engineer in the research team led by Professor Stefan Seelecke, is working on the prototype of the artificial hand.

Source: Dietze O./Saarland University


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