Researchers in the US have developed a thermally conductive rubber material they say could be used in the sportswear sector to create lighted clothing for runners and heated garments for injury therapy.

According to Carmel Majidi and Jonathan Malen of Carnegie Mellon University in Pennsylvania, the development represents a "breakthrough" for creating soft, stretchable machines and electronics.

The new material, known as 'thubber', is an electrically insulating composite that exhibits a combination of metal-like thermal conductivity and elasticity similar to soft, biological tissue, and can stretch over six times its initial length.

"Our combination of high thermal conductivity and elasticity is especially critical for rapid heat dissipation in applications such as wearable computing and soft robotics, which require mechanical compliance and stretchable functionality," explains Majidi, an associate professor of mechanical engineering.

Until now, high power devices have had to be affixed to rigid, inflexible mounts that were the only technology able to dissipate heat efficiently, Malen, an associate professor of mechanical engineering, adds.

"Now, we can create stretchable mounts for LED lights or computer processors that enable high performance without overheating in applications that demand flexibility, such as light up fabrics and iPads that fold into your wallet," he says.

The key ingredient in 'thubber' is a suspension of non-toxic, liquid metal microdroplets. The liquid state allows the metal to deform with the surrounding rubber at room temperature. When the rubber is pre-stretched, the droplets form elongated pathways that are efficient for heat travel. Despite the amount of metal, the material is also electrically insulating.

"As the field of flexible electronics grows, there will be a greater need for materials like ours," adds Majidi. "We can also see it used for artificial muscles that power bio-inspired robots."