Researchers in AMBER, the Science Foundation Ireland-funded materials science centre, hosted in Trinity College Dublin, have discovered a new behaviour of the wonder material graphene.
Efficient ways to pattern and assemble graphene, especially in parallel, have remained a significant challenge for researchers worldwide. But the research breakthrough published in the prestigious journal Nature this week introduces a significant new fabrication method for graphene, as well as creating new technologies that harness the properties of these molecular sheets in ways not previously envisaged.
The researchers, Professor Graham Cross and postdoctoral fellow Dr James Annett of AMBER and the School of Physics at Trinity College Dublin, found that they can induce graphene, a sheet of the element carbon only one atom thick, to spontaneously assemble into ribbons and other shapes while lying on a surface. The effect is potent enough to make large graphene structures almost visible to the naked eye, and it operates in air at room temperature.
In the short term, the researchers expect their findings will be useful to pattern graphene sheets to simplify the production of electronic and other devices in larger volumes. However, they also think the self-assembly effect itself may be important as an active component of future sensors, actuators and machines.
James Annett, who was a graduate student in Cross’ lab at the time of the discovery, said: “I was investigating the properties of graphene as a kind of dry super-lubricant. One day I noticed that cut-out shapes that had been formed during my experiments were changing over time. When I looked more closely, I found that beautiful, well-defined structures had formed in the graphene sheets all by themselves. I realised then that the methods we were using to investigate friction were actually configuring the graphene to spontaneously rearrange itself.”
Fundamentally, the observations reported by the authors in the journal Nature reveal how heat energy causes a flat graphene sheet to try to form its more familiar three-dimensional state known as graphite. A mathematical model to explain why the effect works is included as part of their publication. Cross believes this is a new class of solid matter behaviour specific to molecularly thin sheets.
Professor Graham Cross said: “Over twenty years ago, it was suggested that graphene could be deliberately folded and cut into useful shapes as a kind of molecular origami. Our discovery shows there exists a much richer potential for these kinds of two dimensional materials. We can make them behave like a self-animated sheet that folds, tears and slides while peeling itself away from a surface. Even better, we have figured out how to control the effect and make it happen in different places in the sheet at the same time.”
Graphene is part of a family of recently discovered two-dimensional materials that may revolutionise the electronics used in smart phones and computers, as well as produce light, high-strength composite materials. Now, with the phenomena of self-assembly added to their list of abilities, these materials might enable new devices known as nanoelectromechanical systems, which are connecting up the virtual world to the real world through the Internet of Things.
Source: Trinity College Dublin