'Textile muscles' enabled through electroactive fabric

By coating normal fabric with an electroactive material, Swedish researchers have endowed the fabric with the ability to actuate in the same way as muscle fibres. The technology opens new opportunities to design ‘textile muscles’ that could make it easier for people with disabilities to move.

“Enormous and impressive advances have been made in the development of exoskeletons, which now enable people with disabilities to walk again. But the existing technology looks like rigid robotic suits,” said Associate Professor Edwin Jager, a co-author on the study from Linköping University.

“It is our dream to create exoskeletons that are similar to items of clothing, such as ‘running tights’ that you can wear under your normal clothes. Such a device could make it easier for older persons and those with impaired mobility to walk.”

While current exoskeletons are driven by motors or pressurised air, Associate Professor Jager and his colleagues have instead utilised mass-producible fabric and coated it with an electroactive material. A low voltage applied to the fabric causes the electroactive material to change volume, causing the yarn or fibres to increase in length. The properties of the textile are controlled by its woven or knitted structure, which can be selected depending on how the textile is to be used.

“If we weave the fabric, for example, we can design it to produce a high force,” said co-author Associate Professor Nils-Krister Persson, from the University of Borås. “In this case, the extension of the fabric is the same as that of the individual threads. But what happens is that the force developed is much higher when the threads are connected in parallel in the weave. This is the same as in our muscles. Alternatively, we can use an extremely stretchable knitted structure in order to increase the effective extension.”

Writing in the journal Science Advances, the researchers revealed that the textile muscles can be used in a simple robot device to lift a small weight. They also demonstrated that the technology enables new ways to design and manufacture actuators which — like motors and biological muscles — can exert a force.

“Our approach may make it possible in the long term to manufacture actuators in a simple way, and hopefully at a reasonable cost, by using already existing textile production technologies,” said Associate Professor Jager. “What’s more interesting, however, is that it may open completely new applications in the future, such as integrating textile muscles into items of clothing.”

Image caption: The researchers measure the electrical conductivity of a knitted textile actuator. Image credit: Thor Balkhed/Linköping University.