New research, conducted by engineers at the University of Illinois, results show that the more graphene is bent, the softer it becomes.
The study combines atomic-scale experimentation with computer modelling to determine how much energy it take to bend multilayer graphene. The research team published their findings in the journal Nature Materials.
Graphene is known as the strongest material in the world, researchers say that it is so thin that it is flexible meaning it could be the key ingredient of future technologies.
“The bending stiffness of a material is one of its most fundamental mechanical properties,” said Edmund Han, a materials science and engineering graduate student and study co-author. “Even though we have been studying graphene for two decades, we have yet to resolve this very fundamental property. The reason is that different research groups have come up with different answers that span across orders of magnitude.”
The team discovered why previous research efforts disagreed. “They were either bending the material a little or bending it a lot,” said Jaehyung Yu, a mechanical science and engineering graduate student and study co-author. “But we found that graphene behaves differently in these two situations. When you bend multilayer graphene a little, it acts more like a stiff plate or a piece of wood. When you bend it a lot, it acts like a stack of papers where the atomic layers can slide past each other.”
“What is exciting about this work is that it shows that even though everyone disagreed, they were actually all correct,” said Arend van der Zande, a professor of mechanical science and engineering and study co-author. “Every group was measuring something different. What we have discovered is a model to explain all the disagreement by showing how they all relate together through different degrees of bending.”
Yu fabricated individual atomic layers of hexagonal boron nitride, another 2D material, into atomic-scale steps, then stamped the graphene over the top. By using a focused ion beam, Han was able to cut a slice of the material and image the atomic structure with an electronic microscope in order to see where each graphene layer settles.