From Scotch tape to rubber sealant, glues are an inescapable part of life. Getting them to work at extreme temperatures can be tricky though. Researchers have now made a carbon nanotube-based adhesive that works over a wide temperature range of -196°C to 1,000°C.

Ceramic and epoxy adhesives currently used for high-temperature applications can deteriorate at extreme temperatures. In contrast, the nanotube tape gets stickier as the temperature increases.

The new glue belongs to the class of adhesives inspired by gecko feet. The soles of gecko feet are covered with microscopic hairlike structures that help the lizards cling to solid surfaces through attractive van der Waals forces. Researchers have mimicked these hairy structures with arrays of polymer pillars or vertical carbon nanotubes.

“This is the first time a dry gecko adhesive has been demonstrated for such extreme high and low temperatures,” says Liming Dai, a professor of macromolecular science and engineering at Case Western Reserve University. The adhesive could be used to hold together components in solar cell panels, spacecraft, and in vehicles used in polar regions. “In the vacuum environment of space, all polymer and other dry adhesives dry up and fail,” Dai says. “But this new material can be used in the extreme conditions of space.”

Dai has previously reported a carbon nanotube adhesive that was 10 times stickier than gecko feet with an adhesive strength of 100 N/cm2. It was composed of vertical carbon nanotubes covered with a thin film of jumbled nanotubes.

To make the new high-temperature tape, Dai and his colleagues added a simple twist to previous nanotube adhesives. They grew vertical nanotube arrays on silicon wafers and exposed them to a high-temperature oxygen plasma. This makes the tips of the vertical nanotubes bundle together.

Unlike most dry adhesives made so far, the new adhesive works on rough surfaces, which is necessary for practical applications, Dai says. The researchers made a double-sided tape by growing carbon nanotubes on both sides of a silicon wafer. They sandwiched the tape between two copper foils and tested its adhesion strength by hanging weights from the foils.

The tape had an adhesion strength of 37 N/cm2 at room temperature, the same as 3M double-sided tape. The adhesive strength remained the same down to liquid nitrogen temperatures, and increased almost four times to reach 143 N/cm2 at 1,000°C. And it worked similarly on plastic films, paper sheets, wood pieces, and painted walls. The details are reported in Nature Communications.

Under a scanning electron microscope, the researchers saw that the tips of the bundles penetrated the depressions on the copper surface. As the surfaces are pressed together the nanotube tips spread into web-like structures that increase contact area with the copper and hence the van der Waals forces. When the temperature increases, the copper surface becomes softer, allowing the nanotube tips to penetrate deeper, increasing adhesion.

Zhenhai Xia, a professor of materials science and engineering at the University of North Texas, says that this work advances state-of-the-art adhesives because of its unique temperature-enhanced adhesion and the ability to sustain many temperature transition cycles. But there might be one important hurdle to overcome. “Although this adhesive should work well at low temperature, the long-term stability at high temperatures may be a challenge because carbon is easy to oxidize at high temperatures,” he says.

Read the article in Nature Communications.