For those with obsessive-compulsive tendencies, fingerprints over the screen of their tablet must be a living hell. But a team of German scientists think they can help with, of all things, a candle.
Making a surface that can repel water is easy. So why is it difficult to make one that repels oil? It's to do with oil's low surface tension: to make a surface that can repel it, you need a very particular kind of surface roughness. And while that sounds easy, nobody has yet managed to really work out how to achieve it.
But now a team of researchers at the Max Planck Institute for Polymer Research in Mainz, think they've found a solution... using a combination of candle soot and silica baked at just the right temperature. Look, I didn't say it was hi-tech, right?
They've trialled the idea with glass -- which is notoriously bad for showing up finger prints. First they held the glass over the candle, which caused soot to be deposited on its surface. These little spheres of soot were 30-40nm in diameter, and stacked fairly loosely. In fact, 80 per cent of the coating was empty space, giving just the right roughness required to shed oils.
To fix the soot in place, they coated it with a silica shell 25nm thick. Finally, to get rid of the black colour of the soot, they baked the glass at 600C, making it transparent.
The result? Grease-proof glass! They even managed to take high-speed photos of little drops of peanut oil bouncing up and down from the surface. Fortunately, the coating also sticks to other materials like aluminium, steel and copper, too.