Researchers use graphene ink to produce flexible, water-repellent circuits

Jonathan Claussen and his research group are printing and processing graphene ink to make functional materials. Credit: Christopher Gannon/Iowa State University

Engineers are constantly looking for new ways to graphene printing technology. Researchers from Iowa State university have developed a nanotechnology that uses lasers to produce electronic circuits that are low-cost, flexible and highly conductive and water repellent.

According to a recent paper describing the findings, this technology “would lend enormous value to self-cleaning wearable/washable electronics that are resistant to stains, or ice and biofilm formation,” according to a recent paper describing the discovery.

“We’re taking low-cost, inkjet-printed graphene and tuning it with a laser to make functional materials,” said Jonathan Claussen, an Iowa State University assistant professor of mechanical engineering, an associate of the U.S. Department of Energy’s Ames Laboratory and the corresponding author of the paper recently featured on the cover of the journal Nanoscale.

The group is using inkjet printing technology to create electric circuits on flexible materials—the ink being flakes of graphene.

At this stage, the printed flakes aren’t highly conductive and have to be processed to remove non-conductive binders and weld the flakes together.

Claussen and his research group developed a rapid-pulse laser process that treats the graphene without damaging the printing surface.

And now they’ve found another application of their laser processing technology: taking graphene-printed circuits that can hold water droplets and turning them into circuits that repel water.

“We’re micro-patterning the surface of the inkjet-printed graphene,” Claussen said. “The laser aligns the graphene flakes vertically. And that’s what induces the hydrophobicity.”

Claussen said the energy density of the laser processing can be adjusted to tune the degree of hydrophobicity and conductivity of the printed graphene circuits.

There are many unique applications for this technology including flexible electronics, washable sensors in textiles, microfluidic technologies, drag reduction, de-icing, electrochemical sensors and technology that uses graphene structures and electrical simulation to produce stem cells for nerve regeneration.

The graphene printing, processing and tuning technology is turning out to be very useful, explains Loreen Stromberg, a paper co-author and an Iowa State postdoctoral research associate in mechanical engineering and for the Virtual Reality Applications Center. After all, “electronics are being incorporated into everything.”

In addition to Jonathan Claussen and Loreen Stromberg, co-authors of the paper are: Suprem Das, an assistant professor of industrial and manufacturing systems engineering at Kansas State University, formerly an Iowa State postdoctoral research associate in mechanical engineering and an associate of the U.S. Department of Energy’s Ames Laboratory; Srilok Srinivasan, an Iowa State graduate student in mechanical engineering; Qing He, an Iowa State graduate student in agricultural and biosystems engineering; Nathaniel Garland, an Iowa State graduate student in mechanical engineering; Warren Straszheim, an Iowa State associate scientist with the Materials Analysis and Research Laboratory; Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering, a professor of materials science and nanoengineering and a professor of chemistry at Rice University in Houston; and Ganesh Balasubramanian, an assistant professor of mechanical engineering and mechanics at Lehigh University in Bethlehem, Pennsylvania, formerly an assistant professor of mechanical engineering at Iowa State.

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