Cutting-edge research: Graphene sheets for capturing and storing energy

The next big thing is actually pretty small: an atom-thick lattice of carbon. Graphene sheets may have applications in solar power, computing, IoT and other smart tech.

Researchers have touted graphene as a potential super material since the material's discovery in 2004. Since then, scientists in labs around the world have been working to transform graphene's theoretical potentials into reality -- a move that could bring about the next big wave of revolutionary advancements in numerous areas, including computing, IT and the Internet of Things. The latest advancement in this race to harness graphene's power comes out of the University of Surrey in Guildford, England. Scientists there developed specially treated graphene sheets to create the most light-absorbent material to date. Here, professor Ravi Silva, head of the university's Advanced Technology Institute, shares insights on the breakthrough.

Ravi Silva, head of the Advanced Technology Institute, University of SurreyRavi Silva

How did this research start?

Ravi Silva: The whole project probably started over 10 years ago. We had to produce a very high-absorption material for a defense application. But we had a challenge to produce this highest-absorption material in the smallest volume possible.

The idea was: Could we put this material on very delicate electronic devices? The problem associated with this idea is that as thickness grows, so does the stress associated with the material. If you make it too thin, the more energy that's stored in that thin film, the more likely it will explode the device. So, we needed to think upfront about the materials that can be as thin as possible to reduce the straining between the energy differential and the structure. Looking at all these options, we came to the conclusion to do this well, we needed to use graphene.

Walk me through what you developed.

Silva: It's a physical product. The product that we have is basically a structure you can hold in your hand. So, I can hold something in my hand, and on top of that is a very thin coating. That thin layer of the front surface of the device is the ultrathin graphene layer. Even with a micron microscope, it would be hard to see. But we placed it on another surface, so it's something you can visualize.

What sparked this innovation?

The inspiration actually came from nature. We looked around to see ... the naturally occurring features that are able to absorb things very well. What struck us is the eyes of a moth.
Ravi Silvahead of the Advanced Technology Institute, University of Surrey

Silva: The inspiration actually came from nature. We looked around to see ... the naturally occurring features that are able to absorb things very well. What struck us [are] the eyes of a moth. The eye has the surface texture that allows it to absorb everything it sees. Because it can absorb the tiniest amount of light it sees, it can visualize what's happening around it. And if it absorbs everything, it means they don't reflect anything back. So, it doesn't fall prey to any animals. So, we studied the surface of a moth eye and said, 'Look, if the moth has created these surface features, why don't we see if we can't do a similar sort of structure and we'll coat it with graphene layers?'

How could graphene sheets  advance computing potential?

Silva: We've seen historically in semiconductors something called Moore's law, where transistors get more and more dense. You're making your devices smaller and smaller. In terms of optics, the problem is when you think of a material, as it gets thinner, it absorbs less light. So, when you go below 50 nanometers, you have a transparent layer. You might have a layer that's 50 nanometers thin, but to the outside world, it looks transparent, because it's too thin to absorb light. But you're trying to marry light with electronic circuits. And as soon as your devices get smaller and smaller, it gets invisible. So now, you have to boost the thickness of the optical layer if you want to operate in the wavelength we're comfortable with. In this program, we're making this leap. We're creating surface structures that absorb light.

UK scientists at the University of Surrey looked to nature to invent ultra-thin graphene sheets that are amazing at absorbing light.

What is the capability you created with these graphene sheets?

Silva: You can start miniaturizing optical devices. If you want to make thin layers of light-emitting devices, we can start making devices that are extremely thin. If you want to make a solar cell, typically, it's based on crystalline silicon. It needs about 100 microns of thickness to absorb the sunlight in order to cover the cell. In our case, we can absorb 99% of the light with just 15 nanometers of the material. From an electronic device point of view, it's a significant step in being able to control, capture and store energy. It's all about being able to capture and store energy.

About the author:
Mary K. Pratt, a freelance writer based in Massachusetts, writes frequently about business management and information technology. She can be reached at 
[email protected].

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