Hard-wearing elastic electronics that could be used to make body sensors, artificial skin and tech-embedded clothing have been developed by researchers in Switzerland.

The material, which can be stretched to quadruple its length a million times without damage, represents a step up from previous flexible electronics thanks to both the unique way it is fabricated and the materials it is made from.

Making electronics suitable for soft wearables is known to be a challenge, as converting conventionally hard circuits into ultrathin flexible versions requires the use of completely different materials. At present, market-ready solutions are typically fabric-like, and have little ability to stretch.

However this material, which was developed by researchers from École Polytechnique Fédérale de Lausanne (EPFL), could change that, as it uses liquid metals to provide a surface that remains conductive even when considerably stretched.

The material consists of a stretchy polymer film, with an ultrathin layer of a liquid metal alloy placed on top. While the polymer provides the flexibility and stretch, the metal provides the conductivity.

The metal alloy, a combination of gold and gallium, remains liquid at room temperature, and so can maintain the circuit even when the material is being pulled and flexed.

“Not only does gallium possess good electrical properties, but it also has a low melting point, around 30°,” said study co-author and EPFL Laboratory for Soft Bioelectronic Interfaces PhD student Arthur Hirsch. “So it melts in your hand, and, thanks to the process known as supercooling, it remains liquid at room temperature, even lower.”

However, it was not simply a matter of slapping the liquid metal onto the polymer’s surface; liquid metals have a high surface tension, and previous efforts have resulted in materials far too thick to be suitable. Instead the researchers developed their own method for applying the liquid metal, which allowed it to be applied in a very thin layer.

“Using the deposition and structuring methods that we developed, it’s possible to make tracks that are very narrow – several hundredths of a nanometer thick – and very reliable,” said Stéphanie Lacour, who runs EPFL’s Laboratory for Soft Bioelectronic Interfaces.

While the material is still at a research stage, it is likely to attract considerable interest from the wearable technology industry, which is looking to make technology-embedded clothing the next step on from wrist-worn devices.

The researchers believe the material could be used not only for such clothing, but also for artificial skin in the robotics industry, as well as on-body sensors used to monitor health conditions.