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Scientists use lasers to make metals super water-repellent

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A new method for producing super water-repellent surfaces could lead to self-cleaning materials that are much more slippery than Teflon and never corrode. Researchers from the University of Rochester say they can make metals superhydrophobic (highly water-repellent) using powerful lasers to etch micro and nanoscale structures onto its surface. "The material is so strongly water-repellent, the water actually gets bounced off," said Chunlei Guo, lead author of the study outlining the technique, in a statement. "Then it lands on the surface again, gets bounced off again, and then it will just roll off from the surface."

Unlike chemical treatments, laser-etching can't be rubbed off

Superhydrophobic surfaces have previously been created using chemicals (some sprays are even sold commercially), but this treatment doesn't last longer than a few years and is easily damaged. Guo says that his method is far more lasting as the laser etching is "intrinsically part of the material surface" and can't just be rubbed off. The structures mimic properties found in nature and work by "propping up" water droplets using microgrooves. This reduces the contact angle between the droplets and the surface, making it easier for them to roll away — similar to the difference between dropping a deflated and a pumped-up ball on a flat surface.

Potential applications include extra sanitary and efficient water pipes. (University of Rochester)

The unique properties of superhydrophobic surfaces could have all sorts of real-world benefits, making surfaces easier to clean (water droplets just pick up dust and roll away) and less corrosive. Guo says that one application would be in developing countries where water is scarce. "In these regions, collecting rainwater is vital and using super-hydrophobic materials could increase the efficiency," he says. "A second application could be creating latrines that are cleaner and healthier to use."

It took an hour to create a 1-inch by 1-inch sample

However, using lasers to create superhydrophobic surfaces could face some serious hurdles. It took Guo and his team an hour to treat a 1 inch by 1 inch metal sample, and the laser they used reaches an energy draw "equivalent to ... the entire power grid of North America" at its peak. (The reason this doesn't crash the grid is that it uses extremely short femtosecond laser pulses — each lasting about one-quadrillionth of a second.) Still, the potential benefits certainly merit further research. Guo points out that the etching process can also be used to make surfaces absorb more light, potentially resulting in more efficient solar panels that are also self-cleaning.