When an electrical charge is applied, the nitinol wires contract, just as muscle fibers do. When the charge is turned off, the wires return to their original shape. The wires are strands of nickel-titanium alloy about the width of a human hair.
“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 realized with this first prototype of a robotic hand using shape-memory alloy wires,” Prof. Stefan Seelecke of the Center for Mechatronics and Automation said.
The high energy density of the ‘smart wires’ means they can perform powerful movements in restricted spaces. Bundling them into tendon-like strands presents a greater surface area over which to dissipate heat, meaning 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.
“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,” co-developer and PhD candidate Simone Filomena said.
Although 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.
Check out a video of the bionic hand here.