A new type of paint can create remarkable "self-cleaning" surfaces on a variety of materials, including clothes, paper, glass, and steel.
Water repellent surfaces already exist, but they often stop working if damaged or exposed to oil. This new paint is much more resilient, and is still effective even after being scratched with a knife, scraped with sandpaper, or doused in oil, University College London reported.
"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. 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," said first author Yao Lu of UCL.
The new paint was made from coated titanium dioxide nanoparticles. Different application methods were used based on the material being coated. For example, an artist's spray gun was used to coat glass and steel, while a syringe was used to apply it to paper. All of the materials looked at in the study became waterproof and self-cleaning following the treatment.
"Our paint worked extremely well for a variety of surfaces in tough conditions which were designed to simulate the wear and tear of materials in the real-world. For example, car paint frequently gets scuffed and scratched and we wanted to make sure our paint would survive that. As well as practical uses, the paint could also be used creatively to make art with water which is something I have been exploring in my own time," Lu said.
The experiments were filmed (see below) to provide a closer look at how the treated surfaces behaved. They observed that cotton wool dipped in blue dye emerged without a trace of coloring, and paper remained dry and clean even after it was exposed to dirt and water.
"The biggest challenge for the widespread application of self-cleaning surfaces is finding a way to make them tough enough to withstand everyday damage. 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. We used materials that are readily available so our methods can be scaled-up for industrial applications," said Co-author, Professor Claire Carmalt, professor of Inorganic Chemistry at UCL Chemistry.
The findings were published in a recent edition of the journal Nature.
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