Rubber coating gets a grip on shedding ice

The right half of this licence plate was treated with the new coating(Credit: University of Michigan)

Generally-speaking, hard objects and soft objects don't bond well together. It comes down to a principle known as "interfacial cavitation," in which one surface (the soft one) deforms under pressure, while the other (the hard one) doesn't – as a result, they pop apart. Now, scientists at the University of Michigan have used that principle to develop one of the most ice-repellent coatings ever made. Its applications could range from airplane wings to car windshields to freezers.

In the past, most anti-ice coatings have been rigid and slippery, with the idea being that what repels liquid water should also repel ice. According to the U Michigan team, however, that line of thought was flawed.

Led by associate professor Anish Tuteja, they created an inexpensive composite material made from a blend of commonly-available synthetic rubbers such as polyurethane. The resulting clear spray-on coating is somewhat grippy to the touch. While that might at first seem like it would "hold onto" the ice, the fact is that the hard ice easily releases when the soft rubber deforms – all that's required is the force of gravity, or a slight breeze.

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

By tweaking the composition of the coating, it's possible to select for factors such as durability versus ice repellency. This means that a coating designed for airplane wings could be very durable, as high winds would already blow much of the ice away, while a coating for industrial freezers would be more repellent, allowing ice to be shed with very little effort.

Chances are that the first place the technology will show up, however, is as a lining for frozen food packaging. According to the university, that application could start within a year.

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