Scientists say a newly developed nanocoating -- a "paint" made from coated titanium dioxide nanoparticles -- can create self-cleaning, waterproof surfaces.
The coating has been shown to be waterproof and tough -- robust enough to resist considerable wear -- when applied to paper, steel, glass and even cotton wool, researchers at University College London say.
Titanium dioxide, TiO2, is a cheap and readily obtainable material also used in sunscreen lotions.
"Being waterproof allows materials to self-clean as water forms marble-shaped droplets that roll over the surface, acting like miniature vacuum cleaners picking up dirt, viruses and bacteria along the way," says study first author and UCL chemist Yao Lu.
"For this to happen, the surface must be rough and waxy, so we set out to create these conditions on hard and soft surfaces by designing our own paint and combining it with different adhesives to help the surfaces withstand damage," he says.
To test the coating's toughness, the researches exposed the treated surfaces of various materials to oil and dirt and even went so far as to attempt scratching them with knives and sandpaper.
As opposed to commercially available self-cleaning surfaces, which often degrade when damaged or contaminated, the nanocoating maintained its self-cleaning property in the face of all attempts to impair it, the researchers reported.
The waterproof nanocoating was applied in different ways determined by the material being protected: a spray-gun to coat steel and glass, an application with a syringe and dipping in a coating solution for cotton wool to get the paint on paper.
Because the coating is effective and durable while still being cheap and easy to produce, it could have numerous real-world applications, Lu says.
For example, he says, car paint experiences frequent scuffing and scratching, so his research team wanted to ensure that the paint would survive that.
Making self-cleaning surfaces durable enough to withstand the rough-and-tumble of everyday use has always been a challenge, the researchers noted.
"The surfaces tend to be mechanically weak and so rub off easily, but by pairing our paint with different adhesives, we've shown it is possible to make a robust self-cleaning surface," says study co-author Claire Carmalt, a UCL professor of inorganic chemistry.
The UCL researchers collaborated with scientists at Imperial College London and the Dalian University of Technology in China.
