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Moth-inspired film makes reading in sunlight a lot easier
DECCAN CHRONICLE.
Published Jun 27, 2017, 1:27 pm IST
Updated Jun 27, 2017, 1:27 pm IST
Nature-inspired film is scratch resistant, self-cleaning and could be used on flexible displays.
Inspired
by the nanostructures found on moth eyes, researchers have developed a
new antireflection film that could keep people from having to run to the
shade to look at their mobile devices. (Representational image)
Screens on even the newest phones and tablets can be hard to read
outside in bright sunlight. Inspired by the nanostructures found on moth
eyes, researchers have developed a new antireflection film that could
keep people from having to run to the shade to look at their mobile
devices.
The antireflection film exhibits a surface reflection of just .23 percent, much lower than the iPhone’s surface reflection of 4.4 percent, for example. Reflection is the major reason it’s difficult to read a phone screen in bright sunlight, as the strong light reflecting off the screen’s surface washes out the display. Researchers led by Shin-Tson Wu of the College of Optics and Photonics, University of Central Florida (CREOL), report on their new antireflection coating in Optica, The Optical Society's journal for high impact research.
“Using our flexible anti-reflection film on smartphones and tablets will make the screen bright and sharp, even when viewed outside,” said Wu. “In addition to exhibiting low reflection, our nature-inspired film is also scratch resistant and self-cleaning, which would protect touch screens from dust and fingerprints.”
The new film contains tiny uniform dimples, each about 100 nanometers in diameter (about one one-thousandth of the width of a human hair). The coating can also be used with flexible display applications such as phones with screens that fold like a book, which are expected to hit the market as soon as next year.
Inspired by nature
Many of today’s smartphones use a sensor to detect bright ambient light and then boost the screen’s brightness level enough to overcome the strong surface reflection. Although this type of adaptive brightness control can help improve readability, it also drains battery power. Other methods for solving the sunlight visibility problem have proved difficult to implement.
Looking for a simpler approach to improve screen readability outside, the researchers turned to nature. The eyes of moths are covered with a pattern of antireflective nanostructures that allow moths to see in the dark and prevent eye reflections that might be seen by predators. Because other research groups have experimented with using moth-eye-like nanostructures to reduce the sunlight reflected off the surface of solar cells, Wu and his team thought the same technique might also work on mobile screens.
“Although it is known that moth-eye structures can reduce surface reflection, it is relatively difficult to fabricate an antireflection film with this nanostructure that is large enough to use on a mobile phone or tablet,” said Guanjan Tan, first author of the paper. “Because the structures are so small, a high-resolution and high-precision fabrication technique is necessary.”
The researchers developed a fabrication technique that uses self-assembled nanospheres to form a precise template that can be used to create the moth-eye-like structure on a coating. The simplicity and precision of this process allowed fabrication of the intricate structure in a film large enough to apply to a mobile screen.
The researchers also created a computational model to simulate the optical behavior of the coatings. After showing that the model accurately represented experimental results, the researchers used it to optimize the size of the moth-eye nanostructures to achieve the best performance.
Seeing in the sunlight
Tests of the film after optimization showed that when viewed in sunlight, glass covered with the new film exhibited a more than four-fold improvement in contrast ratio — the difference between the brightest white and darkest black. When viewed in the shade, glass with the new film showed about a ten-fold improvement in contrast ratio. The researchers also used standard industrial procedures to test its flexibility as well as its anti-scratch and self-cleaning capabilities.
“Our measured results indicate the moth-eye-like antireflection film shows excellent optical behavior and mechanical strength,” said Jun-Haw Lee of National Taiwan University, a key member of the research team. “Our film provides an efficient and low-cost method to reduce the surface reflection and improve the sunlight readability of mobile devices.”
The researchers are now working to further improve the anti-reflection film’s mechanical properties, including finding the best balance of surface hardness and flexibility, to make the film surface rugged enough for long-term use on touch screens. They are also using the simulation model to further optimize the moth-eye structure’s shape and size to obtain even better optical performance than ever thought possible.
The antireflection film exhibits a surface reflection of just .23 percent, much lower than the iPhone’s surface reflection of 4.4 percent, for example. Reflection is the major reason it’s difficult to read a phone screen in bright sunlight, as the strong light reflecting off the screen’s surface washes out the display. Researchers led by Shin-Tson Wu of the College of Optics and Photonics, University of Central Florida (CREOL), report on their new antireflection coating in Optica, The Optical Society's journal for high impact research.
“Using our flexible anti-reflection film on smartphones and tablets will make the screen bright and sharp, even when viewed outside,” said Wu. “In addition to exhibiting low reflection, our nature-inspired film is also scratch resistant and self-cleaning, which would protect touch screens from dust and fingerprints.”
The new film contains tiny uniform dimples, each about 100 nanometers in diameter (about one one-thousandth of the width of a human hair). The coating can also be used with flexible display applications such as phones with screens that fold like a book, which are expected to hit the market as soon as next year.
Inspired by nature
Many of today’s smartphones use a sensor to detect bright ambient light and then boost the screen’s brightness level enough to overcome the strong surface reflection. Although this type of adaptive brightness control can help improve readability, it also drains battery power. Other methods for solving the sunlight visibility problem have proved difficult to implement.
Looking for a simpler approach to improve screen readability outside, the researchers turned to nature. The eyes of moths are covered with a pattern of antireflective nanostructures that allow moths to see in the dark and prevent eye reflections that might be seen by predators. Because other research groups have experimented with using moth-eye-like nanostructures to reduce the sunlight reflected off the surface of solar cells, Wu and his team thought the same technique might also work on mobile screens.
“Although it is known that moth-eye structures can reduce surface reflection, it is relatively difficult to fabricate an antireflection film with this nanostructure that is large enough to use on a mobile phone or tablet,” said Guanjan Tan, first author of the paper. “Because the structures are so small, a high-resolution and high-precision fabrication technique is necessary.”
The researchers developed a fabrication technique that uses self-assembled nanospheres to form a precise template that can be used to create the moth-eye-like structure on a coating. The simplicity and precision of this process allowed fabrication of the intricate structure in a film large enough to apply to a mobile screen.
The researchers also created a computational model to simulate the optical behavior of the coatings. After showing that the model accurately represented experimental results, the researchers used it to optimize the size of the moth-eye nanostructures to achieve the best performance.
Seeing in the sunlight
Tests of the film after optimization showed that when viewed in sunlight, glass covered with the new film exhibited a more than four-fold improvement in contrast ratio — the difference between the brightest white and darkest black. When viewed in the shade, glass with the new film showed about a ten-fold improvement in contrast ratio. The researchers also used standard industrial procedures to test its flexibility as well as its anti-scratch and self-cleaning capabilities.
“Our measured results indicate the moth-eye-like antireflection film shows excellent optical behavior and mechanical strength,” said Jun-Haw Lee of National Taiwan University, a key member of the research team. “Our film provides an efficient and low-cost method to reduce the surface reflection and improve the sunlight readability of mobile devices.”
The researchers are now working to further improve the anti-reflection film’s mechanical properties, including finding the best balance of surface hardness and flexibility, to make the film surface rugged enough for long-term use on touch screens. They are also using the simulation model to further optimize the moth-eye structure’s shape and size to obtain even better optical performance than ever thought possible.
Dead Galaxy Discovered By Hubble Leads To More Questions Than Answers
What they saw was totally unexpected. It's enough to challenge a widely accepted assumption about the evolution of galaxies.
As reported in the June 22 issue of the journal Nature, Hubble was able to photograph a dead disk-shaped galaxy that stopped forming stars just a few billion years after the Big Bang. What’s special about the find is that it revealed something unexpected. Instead of seeing a chaotic star formation resulting from the merging of galaxies, what the astronomers saw were stars formed in a pancake-shaped disk. Apparently, this is the first evidence showing that dead galaxies could evolve from a Milky Way-shaped disk into a giant elliptical galaxy.
Elliptical galaxies have older stars while spiral-shaped galaxies have young blue stars. The theory now is that older dead disk galaxies must have undergone major changes that eventually resulted in forming an elliptical galaxy.
Previously, it was widely believed that dead galaxies had a structure that was similar with the elliptical galaxies they would later evolve into. Proving this ideally requires more powerful telescopes than what we currently have. With the help of gravitational lensing, however, it became possible to see into the core of the dead galaxy being studied.
Gravitational lensing is one of the predictions of Einstein’s General Theory of Relativity. It takes off from the concept that massive objects can curve or warp the space surrounding it. As light travels along this curvature, it is deflected toward the massive object. For instance, light from a far-off object like a dead galaxy, could be deflected as it passes through a cluster of galaxies, focusing the dead galaxy’s light in our direction — magnifying it so that it appears larger, brighter, and easier to observe.
By combining all available data (including those from the Hubble and what gravitational lensing provided), astronomers studying the dead galaxy in focus were able to determine that it’s about half the size of our galaxy, is three times as massive, and is spinning more than double the rate at which our own galaxy is spinning. They were also able to figure out the ages of its stars, the rate at which the stars were formed, and the stellar mass.
What remains to be determined now are the following: Why did the galaxy stop forming stars? And how do such galaxies evolve into the elliptical galaxies we have today? According to lead study author Sune Toft from the University of Copenhagen’s Niels Bohr Institute, it’s probably through mergers.
As he described it in a press statement: “If these galaxies grow through merging with minor companions, and these minor companions come in large numbers and from all sorts of different angles onto the galaxy, this would eventually randomize the orbits of stars in the galaxies. You could also imagine major mergers. This would definitely also destroy the ordered motion of the stars.”
Like we mentioned, it’s an amazing discovery. But unfortunately, now there are more questions than answers.
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