PITTSBURGH—"Flubber" was just a joke from the Walt Disney Studios. But "thubber," a thermally conductive rubber material for making soft, stretchable machines and electronics, is now a reality.
Researchers at Carnegie Mellon University, led by mechanical engineering associate professors Carmel Majidi and Jonathan Malen, gave the nickname to an electrically insulating composite that offers what they said is an unprecedented combination of metal-like thermal conductivity and elasticity capable of stretching more than six times its initial length.
The findings of Majidi and Malen were published the week of Feb. 13 in Proceedings of the National Academy of Sciences, according to Carnegie Mellon.
The combination of thermal conductivity and elasticity allows for rapid heat dissipation in applications such as wearable computing and soft robotics, according to Majidi.
Other possible applications for "thubber" include athletic wear (lighted clothing for runners), sports medicine (heated garments for injury therapy), advanced manufacturing, energy and transportation, Majidi said.
With the development of "thubber," high-power devices no longer have to be affixed to rigid, inflexible mounts, according to Carnegie Mellon. Stretchable mounts for LED lights are now possible, as are computer processors that enable high performance without overheating in applications that demand flexibility, it said.
The fabrication of "thubber" works with any soft polymer, but Carnegie Mellon mainly has used silicone in its research, as well as some polyurethane, according to Majidi.
The key ingredient in "thubber" is a suspension of non-toxic liquid metal microdroplets, Majidi said.
"The crucial point is that the metal alloys are non-toxic," he said. "We prepare the alloys ourselves, but there are plenty of suppliers who sell them commercially."
When the rubber is pre-stretched, the droplets form elongated pathways that are efficient for heat travel, according to Carnegie Mellon. The material also is electrically insulating despite the amount of metal, it said.
To demonstrate the material's properties, the researchers used a strap of it to mount an LED light around a jogger's leg, the university said. The "thubber" dissipated the heat from the LED, which otherwise would have burned the jogger, it said.
The researchers also created a soft robotic fish with a "thubber" tail that needed no conventional motors or gears, the university said.
The next phase of the research will involve developing a variety of "thubber" that emphasizes the material's electrical conductivity, according to Majidi.
"It will depend on the elastomers we use and the metal weight fraction," he said.
Carnegie Mellon applied for a provisional patent on "thubber" a couple of years ago, and recently filed for a full patent, according to Majidi.
"It takes years to obtain a patent, but the application still allows us to license the technology through our Technology Transfer Office," Majidi said. Several organizations already have expressed interest, he said.