By the end of 2017 we could start to see a new class of waterproof products that stay hydrophobic for the long haul. That's thanks to a breakthrough by University of Michigan researchers in creating a water-repellent spray-on coating they claim is hundreds of times more durable than similar substances. Even when the coating is damaged, it can heal itself over and over again.

The coating is actually a combination of materials called "fluorinated polyurethane elastomer" mixed with a water-repellent molecule known as "F-POSS." The researchers say that what sets their sprayable, rubbery coating apart from numerous similar products that have come out over the years (Ultra-Ever Dry comes to mind) is its next-level durability.

"Thousands of superhydrophobic surfaces have been looked at over the past twenty or thirty years, but nobody has been able to figure out how to systematically design one that's durable," said Anish Tuteja, an 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."

The substance is so tough that it could waterproof surfaces that current treatments typically struggle to perform on: things like cars, clothes, rooftops and even ship hulls, which could lead to lower resistance in the water resulting in better fuel efficiency for ubiquitous worldwide cargo shipments.

In addition to its longevity and toughness, the team says the coating can also self-heal itself hundreds of times when damaged. It can restore its water resistance "even after being abraded, scratched, burned, plasma-cleaned, flattened, sonicated and chemically attacked," the researchers wrote in a paper recently published in ACS Applied Materials & Interfaces.

Even if molecules of the coating are scraped away from the surface, other molecules will migrate to fill in the gaps and heal the integrity of the hydrophobic surface.

One key to the new coating's impressive water aversion is basically a tweak to the geometry of the hydrophobic surface. Most water-resistant coatings employ microscopic pillars that create air pockets below water droplets. This gives them nowhere to rest and causes them to roll off. But this structure is also fragile. The researchers made their surface slightly pliable so that it can bend but not break in the face of pressure, thereby lasting longer.

Another team in Australia has also attempted to address this fragility by developing a new coating made from a combination of plastics; another models itself on the lotus leaf. Neither of those make the same claims of self-healing properties that help set this new approach apart.

The breakthrough is going to be brought to market by a new company founded by Tuteja called HygraTek, with the help of the University of Michigan. Tuteja is hopeful spray-on coatings and water-repellent fabrics could be available by the end of the year.

Source: University of Michigan

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