by Peace Chiu on Jan 27, 2015 in Products
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Scientists at the University of Rochester have used lasers, not chemicals, to transform metals into highly water-repellant materials

Super-hydrophobic materials are critical for a number of applications, such as rust prevention, anti-icing, or even in sanitation uses. However, as Chunlei Guo, a professor of optics in the University of Rochester, notes, most current hydrophobic materials rely on chemical coatings. This means that if the coating of the material comes off, the material loses its water-repelling properties.
In a recently-published study, Guo and his colleague, senior scientist Anatoliy Vorobyev, have created a game changer in the field of water-repellent materials. According to the university's website, the team used a powerful and precise laser-patterning technique to create an intricate pattern of micro- and nanoscale structures to give metals new properties — one of which is to repel water.
"The material is so strongly water-repellent, the water actually gets bounced off. Then it lands on the surface again, gets bounced off again, and then it will just roll off from the surface," says Guo.

On the advantages of the materials the team has created, Guo adds, "The structures created by our laser on the metals are intrinsically part of the material" — in other words, unlike chemical coatings, the hydrophobic surface won't rub off.
The team also found that as water bounces off the super-hydrophobic surfaces, it also collects dust particles and takes them along for the ride. To test this self-cleaning property, Guo and his team took ordinary dust from a vacuum cleaner and dumped it onto a treated surface. Just a few drops of water were sufficient to completely clean the metal — and best of all, it remained completely dry.
The potential applications of super-hydrophobic materials in developing countries has piqued the interest of the Bill and Melinda Gates Foundation, which has supported the work. "In these regions, collecting rain water is vital and using super-hydrophobic materials could increase efficiency without the need to use large funnels with high-pitched angles to prevent water from sticking to the surface," says Guo. "A second application could be creating latrines that are cleaner and healthier to use."
Latrines are a challenge to keep clean in places with little water. According to the professor, by incorporating super-hydrophobic materials, a latrine could remain clean without the need for water flushing.
There are several issues to be addressed before these applications can become a reality, Guo states. It currently takes an hour to pattern a one inch by one inch metal sample, and scaling up this process would be necessary before it can be deployed in developing countries.
According to the university's website, Guo's team now plans on focusing on increasing the speed of patterning the surfaces with the laser, as well as studying how to expand this technique to other materials such as semiconductors or dielectrics, opening up the possibility of water-repellent electronics.

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