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Researchers from the UK and China have developed a self-cleaning 'paint' that can be applied to a variety of materials and retains its self-cleaning properties after being wiped, scratched with a knife or scuffed with sandpaper.
The paint is made from coated titanium dioxide nanoparticles. When the paint is combined with adhesives it can be applied to materials such as fabrics, glass and steel, to give them self-cleaning properties.
Self-cleaning surfaces work by being extremely repellent to water, but often lose their self-cleaning qualities when they are damaged or exposed to oil. The titanium dioxide-based paint is resilient and can be immersed in oil, making it suitable for use in applications from clothing to cars, the researchers said.
The research, which involved researchers from University College London, Imperial College London and Dalian University of Technology, China, was published in the journal Science this week.
Yao Lu, a researcher from University College London and lead author on the study, said: “Being waterproof allows materials to self-clean as water forms marble-shaped droplets that roll over the surface. 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.
“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.”
Different coating methods were used to create the water-repellent surfaces, depending on the material. An artist’s spray-gun was used to coat glass and steel, dip-coating for cotton wool, and a syringe to apply the paint onto paper.
All the materials became waterproof and self-cleaning as water droplets of different sizes were seen bouncing instead of wetting the surface, removing the dirt applied by the researchers. This was maintained after damage was inflicted on the surfaces.
Co-author, Claire Carmalt, professor of Inorganic Chemistry at UCL, said: “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.”
The experiments were filmed to show the behaviour of the treated surfaces against controls.