Posts Tagged ‘University of Rochester’

Water often damages metals, causing rust, wear and decay.

Thanks to an innovative laser process, however, metal is getting its revenge.

University of Rochester scientists Chunlei Guo and Anatoliy Vorobyev have developed a technique using extremely precise laser patterns that renders metals superhydrophobic: in other words, incredibly water-repellent.

Imagine a much more powerful Teflon — except that Guo and Vorobyev’s material isn’t a coating but part of the metal itself. Water actually bounces off the surface and rolls away.

The possibilities are many, Guo says. Kitchenware, of course. Airplanes: No more worrying about de-icing, because water won’t be able to freeze on aircraft in the first place.

And sanitation in poor countries, an idea close to the heart of the Bill and Melinda Gates Foundation, which helped fund the project. Thanks to the surface’s repellent properties, it’s essentially self-cleaning.

Ironically, Guo was inspired by a project in which he and a team treated a variety of materials to make them superhydrophilic — that is, water-attracting.

“We worked with a variety of materials — not just metal but semiconductors, glass, other things,” he said. Even on a vertical surface, “the effect was very strong. If I drop a drop of water on the bottom of this surface, it would actually shoot up against gravity, uphill. So that really motivated us to look into this reverse process.”

In their paper, the two compared the surface to that of a lotus leaf, which has “a hierarchical structure containing a larger micro-scale structure” and is superhydrophobic.

“Our structure sort of mimics, in some way, this natural (arrangement) of the lotus leaf,” Guo said.

And like the lotus leaf, because the laser-patterned metal is so water-repellent, it has self-cleaning properties. In an experiment, Guo dumped some household dust from a vacuum cleaner on a treated surface. Just a few drops of water collected the dust, and the metal remained dry.

In their work, the scientists used platinum, titanium and brass as sample metals, but Guo says he believes it could work for a wide variety of metals — not to mention other substances.

The process is still very much of the lab. It took the scientists an hour to treat a 1-inch-by-1-inch sample and required extremely short bursts of the laser lasting a femtosecond, or a millionth of a billionth of a second.

But Guo is optimistic about ramping up the process for industrial use, and he says the goal for the sanitation project is to “really push the technology out” in the next two or three years.

And then?

“I do believe down the line we will be able to make it accessible to everyday life,” he said.

Watch out, water.

The scientists’ paper was published in the Journal of Applied Physics. The project was also funded by the U.S. Air Force Office of Scientific Research.

http://www.cnn.com/2015/01/22/us/feat-metal-repels-water-rochester/index.html

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Doctoral student Joseph Choi demonstrates a multidirectional ‘perfect paraxial’ cloak using 4 lenses.


Choi uses his hand to further demonstrate his device.


A laser shows the paths that light rays travel through the system, showing regions that can be used for cloaking an object.

Scientists at the University of Rochester have discovered a way to hide large objects from sight using inexpensive and readily available lenses.

Cloaking is the process by which an object becomes hidden from view, while everything else around the cloaked object appears undisturbed.

“A lot of people have worked on a lot of different aspects of optical cloaking for years,” John Howell, a professor of physics at the upstate New York school, said on Friday.

The so-called Rochester Cloak is not really a tangible cloak at all. Rather the device looks like equipment used by an optometrist. When an object is placed behind the layered lenses it seems to disappear.

Previous cloaking methods have been complicated, expensive, and not able to hide objects in three dimensions when viewed at varying angles, they say.

“From what, we know this is the first cloaking device that provides three-dimensional, continuously multidirectional cloaking,” said Joseph Choi, a graduate student who helped develop the method at Rochester, which is renowned for its optical research.

In their tests, the researchers have cloaked a hand, a face, and a ruler – making each object appear “invisible” while the image behind the hidden object remains in view. The implications for the discovery are endless, they say.

“I imagine this could be used to cloak a trailer on the back of a semi-truck so the driver can see directly behind him,” Choi said. “It can be used for surgery, in the military, in interior design, art.”

Howell said the Rochester Cloak, like the fictitious cloak described in the pages of the Harry Potter series, causes no distortion of the background object.

Building the device does not break the bank either. It cost Howell and Choi a little over $US1000 ($1140) in materials to create it and they believe it can be done even cheaper.

Although a patent is pending, they have released simple instructions on how to create a Rochester Cloak at home for under $US100 (114).

There is also a one-minute video about the project on YouTube.

http://www.smh.com.au/technology/sci-tech/scientists-unveil-invisibility-cloak-to-rival-harry-potters-20140927-10n1dp.html