As wonder materials go, graphene has it all, but why isn’t it being used more widely?
When lasers were invented the hype was quickly followed by a lot of head-scratching. Lasers were incredible. But what were they for? It wasn’t obvious.
It’s the same story with graphene. It is the strongest material known, being 200 times stronger than steel. While diamonds are 3D structures of carbon, graphene is a more intense variation: a 2D layer of carbon just one atom thick.
The link to lasers is clear; it’s a wonder material with many extreme properties. But what is its raison d’être?
Part of the problem lies in its incredible versatility. When the first graphene sheets were produced in 2004 they had a long list of unique attributes.
The first of these is incredible strength. Researchers at the University of Massachusetts-Amherst tested it by firing micro-sized glass bullets into 10 to 100 sheets of graphene at triple the speed of a M16 rifle bullet. It proved twice as tough as kevlar, with 10 times the kinetic resistance of steel.
It’s also stretchy; graphene can be pulled 20% longer than its original size. This is an unusual characteristic for a strong material – diamond shatters when distorted. Potential applications include smart-watches that wrap around the wrist, or electronic newspapers that can be rolled up.
It’s electrically responsive too. Graphene’s conductivity can be altered by applying an external voltage. It can therefore switch from being a highly conductive material, 200 times better than copper, to an insulator with virtually no conductivity. It is because of this that it is described as a ‘chameleon’ material – the scientific term is ‘semi-metal’ – and is 100 times more sensitive than silicon.
At high temperatures free electrons bind with hydrogen, turning graphene into an insulator called graphane. Heat graphane up again and the hydrogen atoms are released. This makes a hydrogen battery feasible.
Last, but not least, graphene is an anti-corrosive. The sheet of carbon forms an impermeable layer that keeps substances apart.
Ahead of its time
This is a remarkable set of attributes. The best applications harness multiple properties, such as the type-II diabetes monitor, which has sensors that detect glucose in sweat. This was invented by a team at Seoul National University and the graphene makes the device thin and flexible. Yet while it’s been proven to work, it remains too fragile for commercial use.
Likewise, computer chips may one day be built from graphene. Scientists at the British Science and Technology Facilities Council fired lasers at a bi-layer of graphene to create a working circuit gate. The goal is to create a faster and smaller replacement for silicon chips. The conductivity of graphene makes it suitable for touchscreens too. A Chinese brand recently produced an Android phone with a bendable graphene-coated screen.
However, other commercial examples are thin on the ground. So rare, in fact, that we’ve seen a backlash. A Financial Times article on graphene last year said ‘graphene languishes in the trough of disillusionment’, having previously scaled the ‘peak of inflated expectations’.
One man with a unique overview of graphene is Terrance Barkan, Director of the Graphene Council, an association of 8,500 academics, PhD students, research departments and manufacturers.
‘The question for your audience is whether graphene is for real. And the answer is yes,’ says Barkan. He says that, in addition to its known properties, graphene has other powerful attributes. For example, it can be used as an additive. ‘It can enhance the strength of other materials by adding 0.5% by weight. With other materials you’d need to add 20% or 30%.’ It is thermally conductive and can be used to dissipate heat.
Barkan is honest about the challenges of making money from graphene. The manufacturing process is complex. ‘Graphene is currently being made at one to three tons per annum per producer. That’s not an industrial scale, but graphene can be used to enhance other materials in small doses.’
The quality of graphene is variable. ‘It’s the wild west right now,’ says Barkan. ‘Some manufacturers call their material graphene when it’s 30, 40 or 50 layers thick. Graphene is up to 10 layers. More than that, it’s micro-graphite.’ Pure single layer, or mono-layer graphene, is very hard to produce without defects.
The focus on whimsical and futuristic products detracts from the more mundane but commercially immediate uses, says Barkan: ‘People have been disappointed that there’s no killer application. No invisibility cloak or battery that lasts a year. That’s the wrong way to look at it. The low-hanging fruit is adding it to existing industrial materials to improve their properties.’
This is the area where the most advanced graphene companies are focusing. Applied Graphene Materials (AGM) is an AIM-listed Durham University spin-out, which makes a suite of graphene products. Chief Executive Jon Mabbitt says AGM uses the lesser-regarded form. ‘Graphene has two forms. One is a thin atomic layer, like a film. The other is small particles, called nanoplatelets, invisible to the human eye, like a black powder.’
This powder is used by AGM to confer an anti-corrosive property to paint. ‘Put onto steel it improves time-to-corrosion by 600%,’ says Mabbitt.
The other area of AGM is composites. ‘Carbon-fibre uses resin, but the resin is brittle. By adding graphene to the resin we can toughen the material significantly.’
On revenues of £300,000 last year, AGM made a loss of £4 million. But investors still have faith and investment across graphene sectors remains high. In 2014 there were 9,000 graphene-related patents. IBM and Samsung are big investors. The £61 million National Graphene Institute in Manchester is proof of the government’s belief.
It took two decades to find a profitable usage for lasers. Graphene may have a future as the building blocks of nano-robots, computer chips or in-body sensors. But right now its use as an industrial additive offers a smooth path to commercialisation.
Graphene is going to be big. Right now, we just don’t know how, or when.
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