researchers at carnegie mellon university have developed an electrically insulating rubber material that demonstrated metal-like thermal conductivity that can stretch to six times its initial length, according to a report on the university website.

researchers created a soft robotic fish with the new 'thubber'. (youtube)

the “thubber,” as the scientists referred to the new material, is composed of suspended, non-toxic, liquid metal microdroplets that deform with the rubber at room temperature. the article explained, “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.”

the researchers were able to demonstrate these properties of the new material by mounting an led light onto a strip of the “thubber” to represent a safety lamp worn on a jogger’s leg. the material dissipated heat from the led, which would otherwise have burned the jogger.

this development has potential applications in wearable and stretchable electronics and soft robotics where rapid heat dissipation is required but mechanical properties are still necessary.

one of the researchers noted, “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.”

the work was recently published in proceedings of the national academy of sciences. the abstract of the report read:

“soft dielectric materials typically exhibit poor heat transfer properties due to the dynamics of phonon transport, which constrain thermal conductivity (k) to decrease monotonically with decreasing elastic modulus (e). this thermal−mechanical trade-off is limiting for wearable computing, soft robotics, and other emerging applications that require materials with both high thermal conductivity and low mechanical stiffness.

“here, we overcome this constraint with an electrically insulating composite that exhibits an unprecedented combination of metal-like thermal conductivity, an elastic compliance similar to soft biological tissue (young’s modulus < 100 kpa), and the capability to undergo extreme deformations (>600% strain). by incorporating liquid metal (lm) microdroplets into a soft elastomer, we achieve a ∼25× increase in thermal conductivity (4.7 ± 0.2 w⋅m⁻¹⋅k⁻¹) over the base polymer (0.20 ± 0.01 w⋅m⁻¹·k⁻¹) under stress-free conditions and a ∼50× increase (9.8 ± 0.8 w⋅m⁻¹·k⁻¹) when strained.

“this exceptional combination of thermal and mechanical properties is enabled by a unique thermal−mechanical coupling that exploits the deformability of the lm inclusions to create thermally conductive pathways in situ.

“moreover, these materials offer possibilities for passive heat exchange in stretchable electronics and bioinspired robotics, which we demonstrate through the rapid heat dissipation of an elastomer-mounted extreme high-power led lamp and a swimming soft robot.”

see the “thubber” in action in the video below: