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Wednesday, January 21, 2015

Extreme Tech- Laser News

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LASERS CREATE SURFACE SO HYDROPHOBIC THAT WATER BOUNCES OFF LIKE A BALL

Lasers create surface so hydrophobic that water bounces off like a ball

By James Plafke on January 21, 2015 at 2:29 pm
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In the study of hydrophobic surfaces, researchers are focusing more on modifying the physical nature of the surface rather than relying on the tried-and-true method of applying a hydrophobic coating. Recently, UCLA engineers created a superomniphobic surface that repelled all known liquids using by modifying a surface — made of nanoscopic nails — rather than applying some kind of special omniphobic coating. Now, researchers at the University of Rochester have used lasers to create a surface so hydrophobic that a single droplet of water can bounce up and down on it — multiple times — like a ball.

Superhydrophobic coatings and surfaces have a wide range of uses — from something as simple as making it safer to drive by wicking rain from a windshield, to preventing rust from compromising the integrity of a structure. Practical applications often come in the form of temporary coatings: rub some Rain-X on your windshield, and greatly increase visibility while driving through a storm as water smoothly slides off the glass.

After a while, though, the Rain-X wears off and must be reapplied. If the surface were inherently superhydrophobic, then it’d not only lose the risk of wearing off at an inopportune moment, but would save money in the long run. While it’s not glass, the University of Rochester researchers have discovered a simple technique to make metal surfaces inherently superhydrophobic: shoot it with lasers.

Chunlei Guo and Anatoliy Vorobyev of the University’s Institute of Optics discovered a laser-patterning technique that etch nanoscopic structures onto a surface. As you can see from the above video, the surface’s etched pattern is so hydrophobic that water literally bounces off, falls back down to the surface, then bounces again. Water rolls off the laser-etched surfaced when it’s titled less than five degrees, whereas a common Teflon pan has to be turned a steep 70 degrees.

Superhydrophobic surfaces are not only good for keeping dry, but for keeping clean. The etched surface also exhibits self-cleaning properties — a test showed that when drops of water slide over the surface, they take dust with them, but leave the surface completely dry. This type of surface could help keep latrines clean in areas of the world where water is scarce.

Scaling up the production of the surface is a focus — currently, it takes around one hour to create a one-by-one-inch sliver. The team is also exploring how to apply the laser-patterning technique to other surfaces. For now, though, this is yet another notch on the hydrophobic belt on the way toward a cleaner and drier future.

Now read: Nissan’s self-cleaning car could kill off car washing forever