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All clear: Keeping glass free from ice with graphene nanoribbons

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[Image above] Credit: Scott Robinson; Flickr CC BY 2.0

It’s officially fall, and it feels so here in Ohio—there’s a crisp cool in the air that holds little hint of any warmth holding over from summer’s sun.

And in addition to feeling like fall, it looking as convincing, too. Football is in full swing. Mums have infiltrated every garden center, grocery store, and front porch. And pumpkins are beginning their annual migration into drinks, dishes, and desserts.

While fall is delightful, that chill in the air also sneeringly hints at what is to come: winter’s cold, snow, and ice. I love the first snow, but winter’s enchantment quickly vanishes the first morning that I have to contort my frigid digits to scrape ice off my car’s windshield.

Wouldn’t it be nice if instead technology could give us a windshield that didn’t ice over?

Rice University researchers report that they are well on their way. They have devised a graphene-laden film that can be applied to glass and plastic to keep their surfaces sans ice, even at frigid temperatures down to –20°C. The research was recently published in Applied Materials and Interfaces.

The work of chemist James Tour and colleagues (whose work on a CO2-grabbing material for natural gas wells we’ve previously covered), the new strategy uses graphene nanoribbons, peeled from graphene nanotubes (a process the Tour lab also pioneered) to apply a coating to glass. While transparent to the eye and to radio frequencies, the coating can transmit heat and electricity.

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Representation of the multistep process to generate a graphene nanoribbon film for glass or plastic surfaces. Credit: J.M. Tour; Rice U.

The fact that the film permits the passing of radio frequency signals may seem like small pennies, but it’s really big stacks. Radio frequency signals are key for proper operation of communication applications, including those integral to the operation of mobile and GPS services like those on that fancy new iPhone 6.

While the team’s previous iterations of the tech mixed the nanoribbons into a polyurethane coating, the new strategy simply spray-coated the nanoribbons onto the surfaces to get a very thin and even coating. The scientists then applied a protective layer of polyurethane on top to keep the nanoribbons intact and in place.

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SEM image of the network of graphene nanoribbons in one of the films. Credit: A.O. Raji; Rice U.

The graphene film, just 50–­200 nm thick, conducts electricity and heat across the glass when a voltage is applied. It melts ice down to –20°C—as cold as your refrigerator’s freezer—and keeps the glass surface clear in the face of extreme fridigity.

“One can now think of using these films in automobile glass as an invisible deicer, and even in skyscrapers,” Tour says in a Rice press release. “Glass skyscrapers could be kept free of fog and ice, but also be transparent to radio frequencies. It’s really frustrating these days to find yourself in a building where your cellphone doesn’t work. This could help alleviate that problem.”

According to the release, Tour also says that the graphene nanoribbons may also eventually find use in creating electronic circuits within glass, which could be used to make smarter devices.

The paper is “Functionalized graphene nanoribbon films as a radiofrequency and optically transparent material” (DOI: 10.1021/am503478w).

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Closeup SEM image of graphene nanoribbons in the network. Credit: A.O. Raji; Rice U.