A pair of researchers from the UCLA Henry Samueli School of Engineering and Applied Science has created the first surface texture that can repel all liquids, no matter what material the surface is made of.
Because its design relies only on the physical attributes of the texture, the texture could have industrial or biomedical applications. For example, the surface could slow corrosion and extend the life of parts in chemical and power plants, solar cells or cookware.
Water will bead up on a nonstick cooking pan because it is coated with a hydrophobic material that repels water thanks to its chemical composition. If the hydrophobic material also is rough at the microscopic scale, it can trap air at its surface, causing the water to bead up and roll around effortlessly. Scientists have named such surfaces “superhydrophobic” to distinguish their unusual zeal to repel water. As an example in nature, water droplets will bead and roll down on some leaves.
“At the microscopic scale, the leaves’ surfaces are 'hairy’ and points of contact with water are reduced,” said Chang-Jin “CJ” Kim, a UCLA professor of mechanical and aerospace engineering, and the study’s principal investigator. “This reduction in points of contact means the water is held up by its own surface tension. Manmade superhydrophobic surfaces have been designed to take advantage of this phenomenon by forming microscale roughness or patterns on a hydrophobic material.”
While a nonstick cooking pan is hydrophobic, it is not “oleophobic,” meaning that it does not repel oil-based liquids. Cooking oil spreads out rather than beading up because it has a lower surface tension than water, making it more difficult to repel. Since the material is not oleophobic, roughening it won’t make its surface oleophobic, let alone “superoleophobic.”
However, in recent years scientists have created certain microscopic textures capable of making surface hydrophobic materials’ surfaces not only oleophobic but also superoleophobic.