A new technique to improve the stretchability of graphene has been devised by researchers from North Carolina State University and the University of Texas. The work done by the researchers has also revealed a great deal about graphene’s mechanical properties that wasn’t previously known — findings which the researchers think should aid in the development of new technologies.
While graphene is an incredibly promising material, there is still so much that is unknown about it that most of its potential is currently just theoretical. More needs to be known about its mechanical properties, especially how it works/interacts with other materials, before its potential can be fully utilized — something which this new work has begun to do.
“This research tells us how strong the interface is between graphene and a stretchable substrate,” states Dr. Yong Zhu, an associate professor of mechanical and aerospace engineering at NC State and co-author of a paper on the work. “Industry can use that to design new flexible or stretchable electronics and nanocomposites. For example, it tells us how much we can deform the material before the interface between graphene and other materials fails. Our research has also demonstrated a useful approach for making graphene-based, stretchable devices by ‘buckling’ the graphene.”
North Carolina State University provides details on the research:
The researchers looked at how a graphene monolayer — a layer of graphene only one atom thick — interfaces with an elastic substrate. Specifically, they wanted to know how strong the bond is between the two materials because that tells engineers how much strain can be transferred from the substrate to the graphene, which determines how far the graphene can be stretched.
The researchers applied a monolayer of graphene to a polymer substrate, and then stretched the substrate. They used a spectroscopy technique to monitor the strain at various points in the graphene. Strain is a measure of how far a material has stretched.
Initially, the graphene stretched with substrate. However, while the substrate continued to stretch, the graphene eventually began to stretch more slowly and slide on the surface instead. Typically, the edges of the monolayer began to slide first, with the center of the monolayer stretching further than the edges.
“This tells us a lot about the interface properties of the graphene and substrate,” Zhu states. “For the substrate used in this study, polyethylene terephthalate, the edges of the graphene monolayer began sliding after being stretched 0.3 percent of its initial length. But the center continued stretching until the monolayer had been stretched by 1.2 percent to 1.6 percent.”
It was also discovered that when the elastic substrate was allowed to return to its original state/length, that the graphene monolayer buckled. This buckling creates ridges in the graphene that made it permanently more stretchable — creating structures like the bellows of an accordion. The researchers note that the technique for creating the buckled material is very similar to the one previously developed for creating elastic conductors out of carbon nanotubes.
The new research was just published on August 1 in the journal Advanced Functional Materials.