Ann Arbor, Michigan – A self-healing, water-repellent, spray-on coating based on a fluorinated polyurethane elastomer has been developed by scientists at the University of Michigan.
The scientists claim it is hundreds of times more durable than alternatives, and a start-up company, HygraTek, is being set up to commercialise the invention.
Water-repellent finishes are rarely strong enough for applications such as clothing or ship hulls. Most work because their surface geometry causes water droplets to roll off. But this leaves them fragile to abrasion, and the Michigan team has found that a slightly pliable surface provides the answer.
The coating comprises a mix of the fluorinated polyurethane elastomer and the water-repellent molecule fluorinated-decyl polyhedral oligomeric silsesquioxane, or F-POSS. It can be sprayed onto almost any surface, and has a slightly rubbery texture that confers a greater degree of resilience. If F-POSS molecules are scraped off the surface, others migrate there to replace them, allowing the coating to renew itself hundreds of times. The healing ability is limited only by the coating’s thickness.
“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, associate professor of materials science and engineering, who led the project. “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.”