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Graphene-based Ink Promises Future Flexible Electronics

Northwestern researchers develop method for producing an ink out of graphene that doesn't lose any of the material's attractive characteristics

2 min read
Graphene-based Ink Promises Future Flexible Electronics

Researchers at Northwestern University’s McCormick School of Engineering have developed a graphene-based ink that could be sprayed onto substrates to make flexible electronics.

While the research thus far has only extended to spraying 14-nanometer-thick layers to create precise patterns, the researchers believe that method they developed for creating the graphene-based ink could lead to flexible electronic devices in the future.

Graphene’s s one atom thick, two-dimensional characteristics have been tantalizing to those interested in flexible electronics.  Just last year, researchers at Cornell University performed work with graphene that suggested that circuits could be made so thin that they would be both flexible and transparent.

The Cornell researchers' approach used traditional chip manufacturing processes like lithography, whereas the Northwestern team has developed a graphene-based ink that could be used for ink-jet printing of electronic circuits.

This use of ink-jet printing means that the Northwestern team had to focus much of its work on finding ways of creating an ink-powder form of graphene without losing any of its attractive electrical characteristics, such as high conductivity.

The research, which was initially published in the Journal of Physical Chemistry Letters (“Inkjet Printing of High Conductivity, Flexible Graphene Patterns”), yielded a method for exfoliating graphite so that it produces small bits of graphene whose electrical conductivity has not been compromised. The method can be done at room temperature using a combination of ethanol and ethyl cellulose to exfoliate the graphite. This technique, say the researchers, reduces residues and leaves a high concentration of graphene flakes that are subsequently put into a solvent, creating the ink.

While the graphene-based ink leads to patterns that are 250 times as conductive as previous attempts to print graphene-based electronic patterns, the paper doesn't discuss whether the material can be engineered to act as a semiconductor. Engineering a band gap into graphene remains a critical prerequisite for applying the material in electronics, and was a preoccupation for the Cornell team in its attempts to use graphene in flexible electronics.

Of course, the focus of the Northwestern team was just to find a way to extract a large amount of graphene during an exfoliation process on graphite and have the resulting material remain highly conductive. But if a method is developed that allows for the doping of the graphene ink so it can be a semiconductor as well as a conductor, we may indeed be moving towards flexible electronics made from graphene.

Image: PARC

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3D-Stacked CMOS Takes Moore’s Law to New Heights

When transistors can’t get any smaller, the only direction is up

10 min read
An image of stacked squares with yellow flat bars through them.
Emily Cooper

Perhaps the most far-reaching technological achievement over the last 50 years has been the steady march toward ever smaller transistors, fitting them more tightly together, and reducing their power consumption. And yet, ever since the two of us started our careers at Intel more than 20 years ago, we’ve been hearing the alarms that the descent into the infinitesimal was about to end. Yet year after year, brilliant new innovations continue to propel the semiconductor industry further.

Along this journey, we engineers had to change the transistor’s architecture as we continued to scale down area and power consumption while boosting performance. The “planar” transistor designs that took us through the last half of the 20th century gave way to 3D fin-shaped devices by the first half of the 2010s. Now, these too have an end date in sight, with a new gate-all-around (GAA) structure rolling into production soon. But we have to look even further ahead because our ability to scale down even this new transistor architecture, which we call RibbonFET, has its limits.

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