One step closer to realising artificial muscles

Breaking new ground 14. may 2024 2 min Professor Anne Ladegaard Skov Written by Kristian Sjøgren

For decades, scientists have dreamed of making artificial muscles that might even be stronger than those of flesh and blood. Now researchers have finally figured out how to make these muscle-like actuators by the metre, and this creates potential for making clothes that can help people to lift heavy objects.

Imagine that when you get dressed, the garment you put on comprises an almost invisible outer shell that makes you stronger.

This outer shell looks like an ordinary garment, but muscle-like actuators are integrated into the fibres to greatly enhance your strength.

Such garments could help people with disabilities or older people to carry shopping bags home from the supermarket without the mechanical help being visible.

For other people, only imagination sets the limit.

For decades, researchers have dreamed of making fibres that can be woven into normal fabric to add new properties, and this has now come one step closer to reality since researchers have developed a method to make these fibres by the metre.

In the near future, the researchers will be attending a major congress where they will present their invention, and they hope to enter into beneficial collaborations with industry to realise the potential of their research.

“Many companies have expressed interest because we have finally developed a method to make long artificial muscle fibres that can be incorporated into textiles. The interest in mechatronics is enormous, and we think we have found a very useful product,” explains a researcher behind the development of the method, Anne Ladegaard Skov, Professor, Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Kongens Lyngby.

The research has been published in Advanced Functional Materials.

Can lift 200 times its own weight

The material the researchers have developed is a silicone elastomer fibre that can change shape when voltage is applied.

A natural muscle contracts when activated by an electrical signal, but the silicone elastomer material expands.

The researchers had originally developed a cling-film-like material, which could stretch further than cling film when energised.

Since then, the researchers developed a method to spin thin tubes from the film, resulting in long hair-like fibres instead.

These fibres can lift 200 times their own weight when energised.

“Imagine an elastic that can become longer when voltage is applied. Our fibres are hollow and twice as thick as a hair, making them suitable for interweaving into fabric,” says Anne Ladegaard Skov.

New method can make muscle-like fibre by the metre

The challenge the researchers have overcome is to make fibres that are long and uniform in thickness and thus commercially viable. The previous achievable length of these fibres was 2 cm, and this was not commercially viable.

However, the researchers from the Technical University of Denmark developed a method to make muscle-like fibres by the metre and roll them up on a coil.

The researchers start with silicone with just the right viscosity, so that the liquid can flow down through a small circular hole that gives the fibres their hollow structure.

The researchers cross-link the elements in the silicone with ultraviolet light that transforms the silicone within 10–15 seconds into an elastic material that can then be slowly wound onto a spool – similar to yarn.

“When voltage is applied to this material, the fibre walls thin and the fibre elongates to conserve its volume, acting similarly to muscle fibres,” explains Anne Ladegaard Skov.

Like wearing a thin wetsuit

Anne Ladegaard Skov thinks that these soft silicone fibres will be useful in developing completely new products with new properties since they can be woven into textiles to produce new properties for garments.

When the time comes to put on such a garment, voltage is applied, the fibres expand.

Once the garment passes over the wearer’s head, the voltage is turned off, and the garment will then fit closely to the body like a very thin wetsuit.

Anne Ladegaard Skov also imagines that a sleeve could be developed that people with disabilities or frail people could wear on their arms under their clothes.

The mechanical strength of the material can help them to lift things that they otherwise could not.

“We have ideas for using these fibres, but we would very much like to collaborate with companies that can incorporate them into their regular production. We also want to further develop the fibres so that they become stronger and can lift even more. And then we would also like to make fibres with different potential applications, including fibres that are not as soft as the ones we have developed now,” concludes Anne Ladegaard Skov.

Fiber-format dielectric elastomer actuators by the meter” has been published in Advanced Functional Materials. The project was supported by the National Natural Science Foundation of China and the Novo Nordisk Foundation.

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