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Research graphene ink for foldable electronics.

Published on May 22nd, 2013 | by Tina Casey


New Printable Graphene Ink Made Possible By Exfoliation

May 22nd, 2013 by  

Forget about that chest wax thing you’ve been thinking about, when it comes to exfoliation a team of researchers at Northwestern Engineering has everybody beat. The team has figured out a way to peel a layer of graphene, the “miracle material of the new millennium,” from a chunk of graphite quicker than you can say “ouch!” and that’s just the beginning. The graphene is being used to develop a low cost, highly conductive ink that can be used to print electronic circuits on flexible material, leading to the next generation of tiny, foldable, mobile electronic devices.

graphene ink for foldable electronics.

Ink pen by janoma.cl.

Getting The Goods On Graphene

Graphene is an ultra-strong carbon material only one atom thick. It was discovered in 2004 by researchers who literally used sticky tape to peel a layer of graphene from a chunk of graphite. Ever since then, the challenge has been to come up with more sophisticated, reliable and commercially scalable ways to obtain sufficient quantities of the finicky material.

One method in current use is to exfoliate graphite through oxidation or with the use of solvents, but both of those techniques interfere with the superior conductive properties of graphene.

The Northwestern graphene team (that’s the Robert R. McCormick School of Engineering and Applied Science, to be precise) developed a conductivity-preserving method that can be carried out at room temperature.

Temperature is a key parameter for commercialization because it translates directly into energy costs, with room or ambient temperature being the most promising. Another potential cost savings is in the team’s choice of solvents, ethanol and ethyl cellulose (ethyl cellulose is a polymer that can be used as a food additive among many other things).

The result  of the process is a powder consisting of a high concentration of nanoscale graphene flakes. Now mix the flakes with another solvent to form a liquid “ink” and Bob’s your uncle.

One layer of the graphene ink is about 14 nanometers thick, and the researchers found that it takes several layers to make a good circuit. Once laid down on a substrate, the circuits retain their conductivity even when the substrate is bent at extreme angles.

A Printable Graphene Ink

As with printable solar cells, printable electronic circuits open up a whole new array of possibilities. Come to think of it, printable solar cells and printable electronics would pack a colossal one-two punch in the context of the rapidly falling price of solar power.

Part of the excitement over printability is due to the fact that inkjet printing is a standard, ubiquitous fabrication method that can be modified with relative ease to accommodate new materials, which means that printable electronics (and solar cells, for that matter) will not require the development of a whole new manufacturing platform.

Inkjet printing can also be applied to a wide variety of materials, including extremely thin films.

We Built This Graphene-a-Palooza!

This is the third major piece of hot graphene news to cross our radar within the past week, the other two being the unlocking of the Hofstadter butterfly mystery and the discovery of magnetic properties in graphene.

For McCormick’s contribution to the field, we can thank the Office of Naval Research, which supported the work.

If that funding source sounds a little odd, consider that the Air Force Office of Scientific Research is among the supporters of another graphene harvesting process that involves dry ice and steel balls (disco, much?).

Needless to say, our favorite pesky meddling government research agency, DARPA (Defense Advanced Research Projects Agency) is also hot on the tail of next-generation electronics based on graphene film, and of course the Department of Energy is all about graphene these days.

What was my point? Oh, right, when the graphene assisted world of the future comes into being, don’t forget to give yourself a pat on the back for contributing some of your tax dollars to make it happen. Yeah, we built this.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

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