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A new way to create electronic circuits using water-repellent graphene could pave the way for a new class of washable electronics.

Researchers from Iowa State University have developed new graphene printing technology that can produce electronic circuits that are low-cost, flexible, highly conductive and water repellent, which would be attractive in a number of applications.

“We’re taking low-cost, inkjet-printed graphene and tuning it with a laser to make functional materials,” 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 study, said in a statement.

The researchers used inkjet printing technology to develop electric circuits on flexible materials. They used flakes of graphene to create the inks used in the study.

While graphene is a great conductor of electricity and heat, the printed flakes are not highly conductive and must be processed to remove the non-conductive binders and then welded together to boost conductivity and make them useful for electronics or sensors.

That process usually involves heat or chemicals, but the researchers developed a rapid-pulse laser process that treats the graphene without damaging the printing surface—even if it is paper.

The laser processing technology can also take graphene-printed circuits that can hold water droplets and turn 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 – like little pyramids stacking up. And that’s what induces the hydrophobicity.”

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

“One of the things we’d be interested in developing is anti-biofouling materials,” Loreen Stromberg, an Iowa State postdoctoral research associate in mechanical engineering and for the Virtual Reality Applications Center and co-author of the study, said in a statement. “This could eliminate the buildup of biological materials on the surface that would inhibit the optimal performance of devices such as chemical or biological sensors.”

The new technology could be used in a number of applications 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 next step for the team will be to conduct more studies to better understand how the nano-and-microsurfaces of the printed graphene creates the water-repelling capabilities.      

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