A new breakthrough: self-healing, water repellent coating

A coating that is water-repellent and can heal itself? It might sound too good to be true, but researchers at the University of Michigan have developed a self-healing, water repellent coating that is hundreds of times more durable than its counterparts.

The spray-on coating could have countless applications, such as clothing (imagine never having to wash your clothes again!), shoes, vehicles, roofing, even the hulls of ships.

The last one particularly has exciting ramifications, as it would decrease the resistance of the ship moving through the water and so significantly cut fuel consumption. Considering that 90% of the world’s cargo is carried by cargo ship, and there are 50,000 merchant ships worldwide, this would be an incredible feat.

Not just a self-healing, water repellent coating, it’s durable too

Water-repellent or ‘hydrophobic’ coatings are not new. What makes this one special is its durability; current waterproofing sprays are too fragile for applications like clothing. The developers say the new concoction is a breakthrough in a field where decades of research have failed to produce a durable coating. Not only is the coating superhydrophobic, it is self-healing, and will remain water repellent after being “abraded, scratched, burned, plasma-cleaned, flattened, sonicated and chemically attacked”. In fact, it will recover from damage hundreds of times.

“Thousands of superhydrophobic surfaces have been looked at over the past 20 or 30 years, but nobody has been able to figure out how to systematically design one that’s durable,” said Anish Tuteja, U-M associate professor of materials science and engineering. “I think that’s what we’ve really accomplished here, and it’s going to open the door for other researchers to create cheaper, perhaps even better superhydrophobic coatings.”

self-healing, water-repellent coating

How does the water repellent coating work?

Researchers looked at the existing water repellent coatings and tried to pick apart what was wrong. They discovered that the two core substances of the coatings, a binder and a water-repellent molecule, were not enough, they needed to remain stable and mix in order to be durable. The team combined a fluorinated polyurethane elastomer with a specialized water-repellent molecule known as F-POSS. The result is this super durable, sprayable, hydrophobic coating. The coating can also heal itself, because if F-POSS molecules are scraped from the surface, new ones will naturally migrate to replace them.

The spray dries into a thin layer that has a rubbery texture, which is what the researchers believe makes it more resilient than its predecessors. The product is currently being commercialized by HygraTek, a company founded by Tuteja with assistance from the U-M Tech Transfer. Tuteja estimates that the coatings will be available for use before the end of 2017, as water-repellent fabrics and spray-on coatings that can be purchased directly by consumers, among other applications.



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