New superomniphobic texture made of nanoscopic nails repels all known liquids

If you have ever lived in a frequently rainy area of the world where the main mode of transportation isdriving, you’re likely very familiar with products like Rain-X. Rub some of it on your windshield, let it settle, and you can practically drive through a downpour without having to turn your windshield wipers on (though we wouldn’t recommend it). Rain-X is a superhydrophobic coating that repels water, giving you a clear view of the road ahead even when wipers can’t. Though superhydrophobic coatings can repel other liquids, its main focus is water, and as your white dress shirt is probably aware, water isn’t the only liquid that can spill. Engineers at UCLA have created a liquid repellent so much more effective than superhydrophobic coating that it’s classified assuperomniphobic — and it’s based on surface texture, rather than a set-and-forget coating.

On a cool, dewy morning, you’ll tend to notice beads of water sitting atop or rolling down leaves. Certain foliage is hairy on a microscopic level, which means the surface doesn’t have enough points of contact with water to soak it in, leaving the droplet intact thanks to its own surface tension. This is also why water beads up on a non-stick cooking pan. If you cook often, though, you’ll know that oil doesn’t bead up; it has a lower surface tension than water, and thus is more difficult to repel. Surfaces have been created that can deal with lower surface tension liquids, such as oil, but being able to repel liquids with an even lower surface tension, like fluorinated solvent — used for electrical cooling, for instance — has remained elusive.

Methanol beading on the new, textured superomniphobic surface

By covering a surface with thousands of microscopic flathead nails, UCLA researchers CJ Kim and Tingyi Liu have created a surface texture that can repel all known liquids. Each nail is thinner than the width of a human hair and placed just 100 micrometers apart, and each head measures in at just 20 micrometers in diameter. Every nail has a vertical overhang coming off its head, looking similar to a tablecloth hanging over the edge of a round table. The overhang buoys liquids by creating a cushion composed of about 95% air, preserving the liquid’s surface tension. The nails are fashioned out of our old friend silica — silicon dioxide; the same stuff that lays at the base of almost every computer chip ever made. [Research paper: DOI: 10.1126/science.1254787]

The UCLA-engineered texture repelled all liquids thrown at it, including oils, solvents, and even a solvent that has the lowest known surface tension for a liquid, perfluorohexane. Even better, the nailed texture can be applied to a variety of surfaces, including metal,glass, and polymers. Due to the surface being made of nanostructured nails instead of, for example, a coating, it’s tough and wouldn’t degrade from harsh temperatures, biofluid, or ultraviolet light.

The researchers have filed a patent for the creation, but need time to explore and perfect it. So for now, you shouldn’t expect to purchase a raincoat covered in the texture anytime soon. The texture exists, though, and can be applied to a variety of surfaces. It seems all the researchers need to perfect the material is time.