Self-cleaning surfaces are extremely repellent to water but may stop working when damaged or exposed to oil. The new paint, which is made using coated titanium dioxide nanoparticles, is resistant to everyday wear and tear and can be applied to clothes, paper, glass and steel.
When combined with adhesives, it maintains its hydrophobic and self-cleaning properties after being wiped or scratched with a knife. In tests, it also survived being scuffed with sandpaper for over 40 cycles. The research team hope that this will make the paint suitable for applications such as car bodies, where frequent scratching can occur, though it could also be used to create art using the water droplets’ patterns, or for easy-clean surfaces in hospitals.
“The surface is highly textured - on a very small scale - but has a waxy, low water affinity surface on top. The water forms spherical shapes when it hits this, and when it rolls off, it takes any dirt with it,’ said Prof Claire Carmalt, Professor of Inorganic Chemistry at UCL Chemistry. “We used two sizes of nanoparticles to make the texture. However, most surfaces like this are mechanically weak. To counter this we used a spray adhesive, which allowed the material to be used on large surfaces.”
The discovery involved researchers from UCL, Imperial College London and Dalian University of Technology (China). 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.