Waterproof, flexible electronics created with graphene ink-jet printer

Water-repellent electronic circuits that can flex and cost little to produce have been made available thanks to new graphene printing technology.

Iowa State University researchers customised an inkjet printer to print with flakes of graphene instead of ink and laid down an electronic circuit on flexible material.

Professor Jonathan Claussen, who led the team working on the project, said the method will “lend enormous value to self-cleaning wearable/washable electronics that are resistant to stains, or ice and biofilm formation.”

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

The printed graphene flakes aren’t very conductive initially and have to be processed to remove non-conductive binders. The flakes are then welded together, which boosts conductivity and makes them useful for electronics or sensors.

That post-print process typically involves heat or chemicals, but Claussen and his research group developed a rapid-pulse laser process that treats the graphene without damaging the printing surface - even if it’s paper.

This method also produced hydrophobic circuits and the energy density of the laser processing can be adjusted to tune the degree of hydrophobicity and conductivity of the printed graphene circuits.

“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.”

“One of the things we’d be interested in developing is anti-biofouling materials,” said Loreen Stromberg who also worked on the project. “This could eliminate the build-up of biological materials on the surface that would inhibit the optimal performance of devices such as chemical or biological sensors.”

The technology could also have applications in 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 researchers wrote that further studies should be done to better understand how the nano- and microsurfaces of the printed graphene creates the water-repelling capabilities.

The Iowa State University Research Foundation is working to patent the technology and is even looking at possible commercialization options.

Last year a team at Duke University developed “spray-on” digital memory also designed for flexible electronics. 

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