New Circuit Types Could Lead to Washable Electronics

Electronics often suffer greatly after being dropped in water or exposed to high-humidity surroundings. However, a breakthrough done by engineers from Iowa State University could lead to water-resistant and even washable electronics.

And this wouldn't be the same type of 'water resistance' promoted by water-proof phones with tight-fitting seals on a device. This resistance goes down to the nano level. 

The discovery is thanks to the supermaterial graphene, which researchers believe can be enhanced to be a low-cost solution to the water/electronics issue. 

"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. Claussen is also an associate of the U.S. Department of Energy's Ames Laboratory and the corresponding author of the paper. The teams' research can be found in the most recent edition of the journal Nanoscale.

Claussen and his team of nanoengineers used standard inkjet printers to make electrical circuits. The ink is simply graphene flakes. Graphene conducts both heat and electricity exceptionally well. It's pliable, transparent, and incredibly strong. And at just a single layer of carbon atoms, graphene is the thinnest material around. 

However, it's not the flakes themselves that hold the key to unlocking these unique hydrophobic properties. It's how they're arranged. As the flakes themselves aren't incredibly conductive, Claussen and his team used non-conductive binders to combine the flakes. This improved their conductivity and would make them perfect for use in sensors and electronics often exposed to water. 

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The team also developed a unique post-print system. Rather than using heat or chemicals to finalize the process, Claussen's team created a rapid-pulse laser. This laser doesn't damage the graphene or the surface on which it's treated -- even if that surface is something like paper. 

"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."

Thanks to this incredibly detailed nanoprinting, the team discovered they could print graphene circuits that can both attract water (aka a hydrophilic circuit) or repel water (aka superhydrophobic circuit). The lasers can even be adjusted to determine just how water repellant a circuit would be. 

The researchers noted that washable electronics could have implications far greater than just making sure a cellphone is safe after it falls into a puddle of water. They want to continue their research and see how this nano-technology can be applied elsewhere -- especially biology.

"One of the things we'd be interested in developing is anti-biofouling materials," said Loreen Stromberg, a paper co-author and an Iowa State post-doctoral research associate in mechanical engineering and for the Virtual Reality Applications Center. "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."

And because "electronics are being incorporated into everything" according to Stromberg, these new types of circuits could be used in everything from microfluid tech to wearable electronics to nerve regeneration.