By Anthony Capkun
March 12, 2016 – Ice build-up on your car is a nuisance, but can be downright dangerous on a powerline or wind turbine, and removing it with current methods—usually chemical melting agents, or scrapers and hammers—is difficult and expensive work. But that may soon change.
University of Michigan researchers say they have developed the formula for a durable, inexpensive spray-on ice-repellent coating that could make ice slide off powerlines, turbines, airplanes and car windshields with only the force of gravity or a gentle breeze.
“Researchers had been trying for years to dial down ice adhesion strength with chemistry, making more and more water-repellent surfaces,” said doctoral student Kevin Golovin. “We’ve discovered a new knob to turn, using physics to change the mechanics of how ice breaks free from a surface.”
Thin, clear and slightly rubbery to the touch, the new coating could also lead to big energy savings in freezers, researchers say, which rely on complex and energy-hungry defrosting systems to remain frost-free. An ice-repelling coating could do the same job with zero energy consumption, making household and industrial freezers up to 20% more efficient.
Made of a blend of common synthetic rubbers, the formula marks a departure from earlier approaches that relied on making surfaces either very water-repellent or very slippery.
Led by Anish Tuteja, the team initially experimented with water-repelling surfaces, but found they weren’t effective at shedding ice. 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 repelled ice because of a phenomenon called interfacial cavitation.
Golovin explains that two rigid surfaces (e.g. ice and 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 deform the rubbery surface, breaking the solid free.
The team has also found that, by slightly altering the smoothness and rubberiness of the coating, they can fine-tune its degree of ice repellence and durability. Softer surfaces tend to be more ice-repellent but less durable, while the opposite is true for harder coatings. Golovin believes that that flexibility will enable them to create coatings for a variety of applications.
“The great thing about our approach is that it’s easy to fine-tune it for any given application,” Golovin said.