When the cold weather hits, ice is not only a nuisance, but a danger. This is especially true when it comes to ice on airplanes, wind turbines and power lines, and unfortunately, current removal methods are typically either labor-intensive or very expensive. Now, University of Michigan scientists have created a durable, inexpensive ice-repellant coating to solve this problem.
The new repellant, made from synthetic rubbers, is a spray-on coating that is thin, clear and slightly rubbery, making it easy to slide ice off of various surfaces using just the force of gravity or a light breeze. The new discovery could provide numerous benefits to a variety of industries, including energy, shipping and transportation.
What separates it from current approaches? Unlike other formulas, the new one does not rely on making surfaces very water-repellant or 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, first author on the study. "We've discovered a new knob to turn, using physics to change the mechanics of how ice breaks free from a surface."
While the team initially tried out water-repelling surfaces, it found that rubbery coatings worked the best for repelling ice, ultimately revealing that the ability of a material to shed water is not important at all. Instead, more important is a phenomenon called "interfacial cavitation."
Interfacial cavitation is the reason that a solid material stuck to a rubbery surface behaves differently than two rigid surfaces interacting. In this situation, even a small amount of force can result in the deformation of the rubber, causing the solid attached to it - in this case ice - to break free.
"Nobody had explored the idea that rubberiness can reduce ice adhesion," said Anish Tuteja, who led the research team. "Ice is frozen water, so people assumed that ice-repelling surfaces had to also repel water. That was very limiting."
Using this new approach, the team created a repellant that possesses improved durability over previous ice-repellant coatings, withstanding numerous lab tests, including salt spray corrosion, high temperatures and hundreds of freeze-thaw cycles.
In addition, by altering the smoothness and rubberiness of the new repellant, the team can tune the degree of ice repellency and durability of the coating, allowing them to create products suited for a wide range of uses.
"An airplane coating, for example, would need to be extremely durable, but it could be less ice-repellent because of high winds and vibration that would help push ice off," Golovin said. "A freezer coating, on the other hand, could be less durable, but would need to shed ice with just the force of gravity and slight vibrations. The great thing about our approach is that it's easy to fine-tune it for any given application."
The findings were published in the March 11 issue of the journal Science Advances.