Using bundles of shape-memory 'smart wire', engineers from Saarland University build a bionic hand that could eventually lead to new flexible and lightweight prostheses. Matthew Stock reports.
The muscle-like wires inside this bionic hand have a remarkable property. When an electrical charge is applied, they contract - just like a muscle. But when the charge is turned off, the wires return to their original shape. Known as 'shape-memory alloy', the fibres are made from strands of nickel-titanium wire, each about the width of a human hair. SOUNDBITE (English) PROFESSOR STEFAN SEELECKE (pron. See-leck-eh), CENTER FOR MECHATRONICS AND AUTOMATION AND THE UNIVERSITY OF SAARLAND, SAYING: "This enables us to build particularly lightweight systems, and the fact that they come in the form of wires enables us to use them as artificial muscles, or artificial tendons. So we can build systems with those that can be like bio-inspired, look-to-nature for a successful prototype, and that's what we realised with this first prototype of a robotic hand using shape-memory alloy wires." The high energy density of these 'smart wires' means they can perform powerful movements in restricted spaces. Bundling them into tendon-like strands presents a greater surface area through which heat can be dissipated. This means they can undergo rapid contractions and extensions, much like real human muscles. No external sensors are needed, with a single semiconductor chip controlling the wire's shape. SOUNDBITE (English) SIMONE FILOMENA, ENGINEERING PhD STUDENT AND CO-DEVELOPER OF THE BIONIC HAND, SAYING: "We can monitor the position of the finger without adding any other sensor; only exploiting this embedded feature of the wire. This helps us to always preserve a very lightweight structure. This is a big deal because normally prostheses until now are very heavy." While the technology is still at an early stage, its potential is huge. The research team hope it could eventually lead to new lightweight prosthetic limbs that function and feel more like natural ones.