March 11, 2016
Spray-on coating could ice-proof airplanes, power lines, windshields
Ice buildup on your car’s windshield can be an annoying problem, but the problem of ice buildup becomes deadly when it happens on the wings of an airplane.
To combat this problem, researchers from the University of Michigan have developed a new ice-repellant coating that facilitates the removal of ice with just the force of gravity or a stiff breeze.According to a press release, the new coating is cheap, durable, see-though, and rubbery to the touch. The team behind its development said the coating could be used to prevent ice buildup on everything from car windshields, to power lines, to freezer defrosting systems. Their work was recently published in an edition of the journal Science Advances.
Water repellent solutions aren't the answer
"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 at the University of Michigan. "We've discovered a new knob to turn, using physics to change the mechanics of how ice breaks free from a surface."
The team had initially looking to expand on the capabilities of water-repellant materials, but experiments kept showing these materials can’t sufficiently be reengineered to shed ice as well as they do water.
Ultimately, the team realized that the ability to repel water is essential to repelling ice. They saw that the crucial attribute is the ability for the coating to deform with even the slightest amount of force, a principle known as "interfacial cavitation."
"Nobody had explored the idea that rubberiness can reduce ice adhesion," said team member Anish Tuteja, associate professor of materials science and engineering at the University of Michigan. "Ice is frozen water, so people assumed that ice-repelling surfaces had to also repel water. That was very limiting."
The team has discovered that by marginally changing the smoothness and rubberiness of the coating, they could fine-tune its level of ice repellency and durability. Softer surfaces were found to be more ice-repellent but less durable, while the reverse was found for harder coatings. Golovin said that versatility will enable them to develop coatings for a massive range of applications.
The new coatings also stood up to a various lab tests including peeling, corrosion, temperature, abrasion and freeze-thaw cycle trials.
"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."
"I think the first commercial application will be in linings for commercial frozen food packaging, where sticking is often a problem. We'll probably see that within the next year," Tuteja added. "Using this technology in places like cars and airplanes will be very complex because of the stringent durability and safety requirements, but we're working on it."