Superhydrophobic surfaces are smart, but not that tough.
They repel water brilliantly but are easy to cut, scratch and dent. And once the surface is damaged, the performance isn’t that brilliant. Water just sits in the damaged areas.
Now researchers from China and Finland say they have developed an armour-plated superhydrophobic surface that can take a repeated battering from both sharp and blunt objects and still do its job.
“The armour can be made from almost any material, it’s the interconnection of the surface frame that makes it strong and rigid,” says Robin Ras, a physicist at Finland’s Aalto University.
Writing in the journal Nature, he and colleagues explain that the superhydrophobic properties come from having nano-sized structures spread all over the surface.
The trick, they say, is to pattern the surface with a honeycomb-like structure of tiny inverted pyramids. The fragile water-repellent chemical is then coated on the inside the honeycomb.
This prevents any liquid from sticking to the surface, and the fragile chemical coating is protected from damage by the pyramid’s walls.
“We made the armour with honeycombs of different sizes, shapes and materials,” says Ras. “The beauty of this result is that it is a generic concept that fits for many different materials, giving us the flexibility to design a wide range of durable waterproof surfaces.”
To test their readiness for work, the researchers subjected their new surfaces to extreme conditions, including baking them at 100 degrees Celsius for weeks, immersing them in highly corrosive liquids for hours, blasting them with high-pressure water jets, and subjecting them to physical exertion in extreme humidity.
Superhydrophobic surfaces are extremely useful for antimicrobial coatings, because bacteria, viruses and other pathogens can’t cling to them, but they also have broader applications, the researchers say. One example is solar panels; the build-up of moisture and dirt blocks the amount of light they can absorb, reducing electricity production.