Researchers at Northwestern University have devised a new method of creating large volumes of high-quality graphene, and then printing flexible graphene patterns with an inkjet printer that are 250 times more conductive than previous attempts.

When it comes to the next generation of electronics and computing, graphene has a unique combination of properties that make it an almost ideal material. Not only is it extremely conductive, but it’s very strong, chemically stable, and flexible. There are just two problems: It’s very hard to produce pure graphene in large quantities, and it’s proving quite hard to use graphene as a semiconductor (it doesn’t contain the all-important bandgap). Today, it seems like Northwestern may have solved the first problem — but the bandgap issue still remains at large.

Historically, graphene is produced through mechanical exfoliation — a fancy term that essentially means “peeling off layers of graphite using sticky tape.” This produces high-quality graphene, but it’s impossible to scale up to commercial production. Researchers have recently grown pure graphene on a copper substrate, using chemical vapor deposition (CVD), but it’s still a very slow process, and it’s unlikely to produce graphene in the quantities that we require. The better option for mass production is solution-phase exfoliation — flaking off graphene from graphite using a liquid solvent — but previous attempts have only produced very low quality flakes that don’t possess many of graphene’s “wonder material” properties. Now Northwestern has devised a new method, using ethanol and ethyl cellulose, that can be used to mass produce flakes of fairly high quality graphene.

These flakes are then mixed into an ink, which is then printed using a conventional inkjet printer. The resulting circuits, as you can see on the right, are highly flexible — and even under such stress, their conductivity (which is 250 times higher than previous inkjet-printed graphene circuits) remains virtually unchanged. In theory, these inkjet-printed graphene circuits could form the basis of flexible, foldable devices. Imagine a display that is made up of individual panels, which can be unfolded to make a giant display — much like a folded tourist map. The other obvious application is wearable computing, where various components might be stored in fairly static locations (against your chest, your inside leg), but the connections between the components would be fashioned from flexible graphene.

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Research paper: DOI: 10.1021/jz400644c – “Inkjet Printing of High Conductivity, Flexible Graphene Patterns”