Carbon nanotubes have been found to act like super-compressible springs, which could allow the creation of foam-like materials for everything from disposable coffee cups to new space shuttle insulation.
Research reported in the journal Science shows that films of aligned multiwalled carbon nanotubes can act like a layer of mattress springs and rebound in response to force. Unlike a mattress, however, the foams retain resilience even after thousands of compression cycles—there is no tradeoff between strength and flexibility.
“Carbon nanotubes display an exceptional combination of strength, flexibility, and low density, making them attractive and interesting materials for producing strong, ultra-light foam-like structures,” says Pulickel Ajayan, coauthor of the paper.
A news release reports details of the work:
Carbon nanotubes are made from graphite-like carbon, where the atoms are arranged like a rolled-up tube of chicken wire. Ajayan and a team of researchers at the University of Hawaii at Manoa and the University of Florida subjected films of vertically aligned nanotubes to a battery of tests, demonstrating their impressive strength and resilience.
“These nanotubes can be squeezed to less than 15 percent of their normal lengths by buckling and folding themselves like springs,” says lead author Anyuan Cao, who did much of the work as a postdoctoral researcher in Ajayan’s lab and is now assistant professor of mechanical engineering at the University of Hawaii at Manoa. After every cycle of compression, the nanotubes unfold and recover, producing a strong cushioning effect.
The thickness of the nanotube foams decreased slightly after several hundred cycles, but then quickly stabilized and remained constant, even up to 10,000 cycles. When compared with conventional foams designed to sustain large strains, nanotube foams recovered very quickly and exhibited higher compressive strength, according to the researchers. Throughout the entire experiments, the foams did not fracture, tear, or collapse.
And their intriguing properties do not end there. Nanotubes also are stable in the face of extreme chemical environments, high temperatures, and humidity all of which adds up to a number of possible applications, from flexible electromechanical systems to coatings for absorbing energy.