On your car windshield, ice is a nuisance. But on an airplane, a wind turbine, an oil rig or power line, it can be downright dangerous. And removing it with the methods that are available today--usually chemical melting agents or labor-intensive scrapers and hammers--is difficult and expensive work. That could soon change thanks to a durable¹, inexpensive ice-repellent coating developed by University of Michigan researchers. Thin, clear and slightly rubbery to the touch, the spray-on formula could make ice slide off equipment, airplanes and car windshields with only the force of gravity or a gentle breeze. This could have major implications in industries like energy, shipping³ and transportation, where ice is a constant problem in cold climates.

 

The new coating could also lead to big energy savings⁴ in freezers, which today rely on complex and energy-hungry defrosting systems to stay frost-free. An ice-repelling⁵ coating could do the same job with zero energy consumption, making household and industrial freezers up to 20 percent more efficient. The coating is detailed⁶ in a new paper published in the journal Science Advances.

 

Made of a blend of common synthetic⁷ rubbers, the formula marks a departure from earlier approaches that relied on making surfaces either very water-repellent or very slippery.

 

"Researchers had been trying for years to dial down ice adhesion strength with chemistry, making more and more water-repellent surfaces," said Kevin Golovin, a doctoral student in materials science and engineering. "We've discovered a new knob to turn, using physics to change the mechanics of how ice breaks free from a surface."

 

Led by Anish Tuteja, associate professor of materials science and engineering, the team initially⁸ experimented with water-repelling surfaces as well, but found that they weren't effective at shedding ice. But during their experiments, they noticed something unexpected: rubbery coatings worked best for repelling ice, even when they weren't water-repellent. Eventually, they discovered that the ability to shed water wasn't important at all. The rubbery coatings repelled⁹ ice because of a different phenomenon, called "interfacial cavitation."

 

Golovin explains that two rigid¹⁰ surfaces--say, ice and your car windshield--can stick tightly together, requiring a great deal of force to break the bond between them. But because of interfacial cavitation, a solid material stuck to a rubbery surface behaves differently. Even a small amount of force can deform¹¹ the rubbery surface, breaking the solid free.

 

"Nobody had explored the idea that rubberiness can reduce ice adhesion," Tuteja said. "Ice is frozen water, so people assumed that ice-repelling surfaces had to also repel² water. That was very limiting."

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