By Rebecca Tan
What’s the thinnest material in the world? Graphene. What’s the stiffest material in the world? Also graphene. What about the most stretchable material in the world? You guessed it, graphene. But for all its amazing properties, making graphene turns out to be very simple: all you need is some sticky tape and a lump of ordinary graphite.
“Despite being so simple superficially, graphene has turned out to be a material with superlative properties,” said Sir Andre Geim, winner of the 2010 Nobel Prize in Physics for his discovery of graphene, addressing the crowd at the Global Young Scientists Summit 2017 (GYSS 2017).
Don’t throw away your Nobel Prize
For researchers working with atomic force microscopes, sticky tape and graphite are little more than peripherals of the trade. Sticky tape, Sir Andre explained, is used to clean the surface of graphite for microscopy work, and subsequently thrown away.
“They didn’t realise that they were throwing away their Nobel Prizes as well,” he shared with a laugh.
“Unlike thousands of my predecessors, I took the tape to the microscope and saw that light shone through the specks of graphite left on the surface,” Sir Andre said. “For me, this was an eureka moment, because it suggested that the graphite was very thin, less than ten layers thick in fact. I was shocked that it was possible to make such thin films.”
Thin films—one to a few atoms thick—don’t exist in nature because of vibration, which makes anything less than three dimensional unstable. According to Sir Andre, scientists had for many years assumed that it was impossible to grow one or low dimensional materials due to these theoretical constraints.
“But forbidden in nature doesn’t mean it can’t be made artificially,” he added. “What the trick with sticky tape helped us to do was to take a three dimensional material and extract an individual atomic plane from the bulk or surface.”
Thin is in
Before you start peeling sticky tape off everything and sticking it under a microscope in the hopes of winning a Nobel Prize, remember that graphene has unique properties that helped establish a whole new subdiscipline: thin film material science.
“If extracting an individual atomic plane out of the graphite crystal were the whole story, I wouldn’t be speaking here today,” acknowledged Sir Andre.
One of the most fascinating properties of graphene might be its ability to bridge the quantum and classical worlds. Because of the way the electrons in graphene are arranged, graphene can mimic particles at the speed of light, allowing approximations of experiments that would otherwise require expensive equipment like particle accelerators.
Beyond its experimental value, graphene has already found its way into everyday objects like tennis rackets, helmets and even watches, Sir Andre said. He noted that all these real-world applications were mere speculation as little as five years ago. Since then, people have managed to grow graphene in square metre wafers, and it can now be bought relatively cheaply.
“Today, we know about 100 different materials that are one atom or molecule thick—the brothers and sisters of graphene, or what I call graphene 2.0,” Sir Andre said. “We’re taking this one step further with graphene 3.0, playing Lego games on an atomic scale by assembling different layers into new materials with specific properties.”
Of fame and frogs
Despite Sir Andre’s pivotal role in the discovery of graphene, he is still remembered by some for his earlier work in magnetism. Finding himself in an outdated magnetic facility in the Netherlands earlier in his career, he decided to test a simple question: What would happen to water in a high magnetic field?
“So on a Friday night I switched on the magnet and poured in water, expecting that the water would end up on the floor,” Sir Andre said. “But after a few minutes of tinkering, I found something completely different—the water was levitating!”
After a few minutes of utter surprise, Sir Andre realised that he could not have created an anti-gravity machine. An hour of putting formulas together later, he figured out that what he had observed was magnetisation of the water, a phenomenon scientists have known about for 150 years.
“When I came into the lab the next day and said, ‘Look, water levitates in a magnetic field,’ everyone laughed at me. Colleagues who had been professionally dealing with high magnetic fields for a long time—from PhD to pension—didn’t believe me and I had to show it to them again and again,” he said.
But his colleagues eventually came around and they started sticking all sorts of things—from wine and beer to strawberries and tomatoes—into the magnet. Eventually, Sir Andre decided that they should do something iconic and made a short movie of a levitating frog.
“It was a very hard experiment because, as condensed matter physicists, we deal with dead things, not things that jump and stick to your fingers!” Sir Andre said. “But as a result of this kind of Friday night experiment, the levitating frog has appeared in many textbooks and to this day I still have people at conferences coming up to me and saying, ‘Listen, I have no idea what graphene is; but I know your frog!’”
Right under our noses
For Sir Andre, the discovery of graphene and his ‘discovery’ of levitation are all examples of how astounding science can sometimes be found in everyday things.
“In every pencil trace, you can find a single layer of graphite which is essentially graphene, the Nobel Prize-winning material. Graphene was literally in front of our eyes and under our noses for at least 500 years but we didn’t notice this material until the beginning of this millennium. This tells you how little we know about the world, and how much more remains to be discovered,” he concluded.
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