Superhydrophobic coatings hold a wide array of potential consumer and industrial applications. However, most aren't overly durable, meaning their water repelling properties can be easily lost. Now scientists at the Australian National University (ANU) have developed a new spray-on superhydrophobic coating that is much more robust than existing solutions and low-cost to manufacture and apply.
Hydrophobic materials generally get their water-repelling properties from rough surfaces made up of tiny pillars, which trap a layer of air between them that prevents the liquid from getting a good grip on the surface of the object. We reached out to William Wong and Antonio Tricoli, two of the ANU researchers, who told us that the problem is that these complex surfaces are vulnerable to damage, which can reduce the long-term effectiveness of the material.
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"Superhydrophobic materials are typically very fragile due to the need for delicate preservation of surface morphologies," the researchers told New Atlas. "Fluoro-functionalized nanostructured silica (F-SiO2), for example, is a highly performing superhydrophobic material, however, its commercial application remains largely impeded by poor mechanical durability resulting in the rapid loss of superhydrophobicity upon abrasion damages."
We last saw the team making a material that rolls itself into a tube when exposed to liquid, and this time they've set about improving that durability. According to the team, their new material, made using a combination of two plastics, polymethyl methacrylate and polyurethane, is up to 60 times more functionally robust than their control materials. Mechanically, the coating is very stable and in tests was found to be resistant to long-term abrasion damage without losing its superhydrophobic properties.
"Their cross-linking and material-synergistic properties create a much more robust hybrid (interpenetrated polymer networks) than either of these alone," say the researchers. "Think of this as two interwoven sets of fishing nets, made of different materials with different properties."
The coating also resisted damage from acids, UV light and solvents like cleaning alcohols, and this durability should help make the material a one-off, spray-on protection. That puts it ahead of other materials like Ultra-Ever Dry, which its manufacturer claims can go eight months to a year before needing a new coat.
"We have not yet tested it for every use but believe that for most applications it will be a long-term coat that does not require reapplication," the ANU team explains.
The team has actually developed two ways to crate the coating, both of which they claim are cheaper and easier than the processes used to create similar coatings. Additionally, the material is transparent, too, so its applications may extend to coating consumer electronics like smartphones, street signs, packaging materials like cardboard or wood, or to protect boats from water damage and planes from ice formation.
"It will keep skyscraper windows clean and prevent the mirror in the bathroom from fogging up," says Tricoli.
Beyond waterproofing, the same principles could be applied to make similar coatings that are anti-corrosive, self-cleaning or oil-repellent.
The research was published in the journal ACS Applied Materials and Interfaces
The team describes their work in the video below.
Source: Australian National University