Plastic fantastic

Irish scientist Jonathan Coleman, of Trinity College, made the Top 100 materials scientists in the world. He explains what he did to deserve it

WHEN A MUSICIAN releases an album or single, the number of downloads or CDs it sells sends it flying up the charts. You could argue that for researchers, the equivalent is having your published paper cited by others.

Those scientific citation charts exist, and there was a flurry of excitement earlier this year when Irish scientist Prof Jonathan Coleman made the Top 100 materials scientists of the decade worldwide between January 2000 and October 2010, as compiled by Thomson Reuters.

His position of 61, with 30 papers and 1,507 citations, put him within the top 0.02 per cent in the field. “We were very pleased with that,” says Coleman, an associate professor at Trinity College Dublin’s school of physics and a principal investigator at the Science Foundation Ireland-funded Centre for Research on Adaptive Nanostructures and Nanodevices (Crann).

Trinity caught Coleman early on in a career that has seen him crack problems in material science that could lead to lighter plastics, better batteries and even more efficient electronic screens. His first rung on the research ladder was to look at ways of toughening up plastics: his PhD in the 1990s looked at how to mix tiny structures called carbon nanotubes into plastics to beef them up.

There was nothing new about the general approach of reinforcing a material with fibres, he notes. “People have known this sort of technology for quite a long time – there are mudbrick structures in the Sahara desert that are basically mud reinforced with straw: people have been doing that for thousands of years. We were doing exactly the same thing except in this case we were working with plastics, and rather than straw we had these small tubes.”

A few years later Coleman spent a “phenomenally productive” three months in the University of Texas, where a project sought to use carbon nanotubes to create super-stiff fibres – the kind that would be helpful in bulletproof vests.

But Coleman and another researcher noticed the fibres they were working with were tough rather than stiff, so they developed that aspect instead and got a publication in the high-profile journal Nature to boot.

“We went from the beginning of that project to having the toughest fibres known to man in three months,” he says.

“But the problem really is that carbon nanotubes are expensive – $500 per gram – and you need to get the cost down before it will be used in industry, that’s the big barrier.”

A more recent discovery by Coleman and his lab could offer a way to vault that cost barrier for another carbon material with remarkable properties: graphene.

Discovered in 2004, graphene is a two-dimensional sheet of carbon that has exceptional strength and conductivity. But getting the individual layers involved peeling them off graphite (yes, that cheap-as-chips stuff in your pencil) one flake at a time. “That was never going to be good for anything in terms of industry,” notes Coleman.

He knew how to easily disperse carbon nanotubes in a liquid, and looking at the equations behind the process, he figured the same should work with graphite. So his lab tried it.

“If we could apply our technique we could make a trillion layers of graphene at a time rather than one or two,” he recalls. “We immediately tried that and it worked first time.”

Using their graphene exfoliation technique, his lab has doubled the strength and stiffness of plastics, which has the potential to reduce our reliance on oil to make it, but at a fraction of the price incurred by carbon nanotubes.

Coleman has now turned his attention to other industrially relevant layered materials, and he got a grant from the European Research Council to work with materials with applications in energy generation and storage.

Screen displays on electronics also stand to benefit from his ability to manipulate materials at this nano level.

“Every screen, TV and computer has transparent electrodes on the front face to allow the light out, but the material used, indium tin oxide, is becoming scarce and expensive, so people are looking for alternatives,” he says.

His lab worked on a project with Hewlett Packard that found how to make thin transparent films using silver nanowires that can act as electrodes. “We have found a method that can deposit thin films of silver nanowires over very large areas in an industrially friendly process,” says Coleman. “This was one of the big outstanding problems in applied nanotechnology and it has been solved in Ireland.”

And Coleman muses that he could probably not have achieved as much as he has in Ireland were it not for the investment into research here in recent years. “I’ve been in Trinity the whole time and have been quite successful, and because of SFI’s investment it’s only now that that is possible,” he says. “Before, there was no way that could happen.”