Is it a bird? Is it a plane? No, it's... er, Graphene bubbles – 200 times stronger than Superman
Miracle material bests Man of Steel, withstands incredible pressure, say eggheads
Tiny graphene bubbles can withstand enormous pressures and are 200 times stronger than steel, according to scientists at the University of Manchester in the UK.
Results published today in Nature Communications reveal yet another superior property in graphene, also known as the "miracle material."
Stacking graphene on top of two-dimensional substrates like boron nitride enhances graphene's electrical properties. Strong cohesion between both materials should lead to an atomically clean interface with few impurities.
Any contaminants left inbetween the two layers, however, become trapped and are squeezed out by the van der Waals forces between graphene and the substrate, and form submicron-sized "bubbles."
The process is similar to what happens when dust particles cause bubbles of air to form under a layer of film when a screen protector is stuck onto a mobile phone. The bubbles are largely ignored and considered a nuisance.
The team of researchers at Manchester, however, decided to take a closer look at them, only to discover that the bubbles under high pressures could be useful.
The pressure exerted by graphene onto the bubbles or vice versa was measured by using the tip of an atomic force microscope to make an indentation on the bubbles, a layer of molybdenum disulphide and boron nitride.
The force required to make the indent was measured for graphene-enclosed bubbles. Researchers found that the smaller the bubble, the higher amount of pressure it could withstand. Micron-sized bubbles can hold about 200 megapascals, while bubbles smaller than 10 nanometres can take 1 gigapascal of pressure.
Smaller bubbles were more likely to be round and larger bubbles were pyramidal or triangular in shape.
Sir Andre Geim, who was awarded a Nobel prize for his work on graphene and was coauthor of the study, said: "Those balloons are ubiquitous. One can now start thinking about creating them intentionally to change enclosed materials or study the properties of atomically thin membranes under high strain and pressure."
Graphene bubbles are a new area of research and the applications are still being explored. Another team at the University of Manchester carried out experiments looking at how the curvature of the bubbles could be used to make lenses.
Ekaterina Khestanova, a PhD student who performed the experiments, believes the pressurised bubbles could be used to prevent liquids from freezing.
"Such pressures are enough to modify the properties of a material trapped inside the bubbles and, for example, can force crystallization of a liquid well above its normal freezing temperature," she said. ®