Moth-inspired film makes it easier to read screens in sunlight
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A scratch-proof, self-cleaning and anti-reflective film of nanostructures developed at the University of Central Florida has shown promise in making it easier to read devices in the sunlight.
The reflection of light is the main reason why it is difficult to read the screen of a phone on a sunny day, as the light “washes out” the display. Many smartphones today use a sensor to detect bright light and turn up screen brightness in response. While this can improve readability, it also drains battery power.
A team of researchers in the College of Optics and Photonics at the University of Central Florida turned to moths for inspiration to solve this problem. Moths’ eyes are covered with antireflective nanostructures which prevent eye reflections that may be noticed by predators.
Other researchers have attempted to replicate this structure to reduce reflection from solar cells and improve their performance.
“Although it is known that moth-eye structures can reduce surface reflection, it is relatively difficult to fabricate an anti-reflection film with this nanostructure that is large enough to use on a mobile phone or tablet,” said Professor Guanjan Tan, first author of the study. “Because the structures are so small, a high-resolution and high-precision fabrication technique is necessary.”
The University of Central Florida team developed a simple new technique – using self-assembled nanospheres to form a template to create the moth-inspired structures on a coating – which allowed for fabrication of the nanostructures on a sufficiently large film.
The film contains uniform “dimples” of 100 nanometres across. This is approximately one-thousandth the width of a human hair. The film has a surface reflection of 0.23 per cent; far lower than an iPhone’s surface reflection of 4.4 per cent, for example.
After testing their new product, the researchers found that glass covered with the film showed a more than fourfold improvement in contrast ratio in sunlight and a tenfold improvement in the shade.
“Using our flexible anti-reflection film on smartphones and tablets will make the screen bright and sharp, even when viewed outside,” said Professor Shin-Tson Wu, who led the team. “In addition to exhibition low reflection, our nature-inspired film is also scratch resistant and self-cleaning, which would protect touch screens from dust and fingerprints.”
Next, the researchers will work to improve the mechanical properties of the film, such as by finding the ideal balance of hardness and flexibility to render it tough enough for constant handling on a touchscreen. They hope that the flexibility of the film will allow it to be used with novel applications such as foldable phones, which could become widely commercially available in the following years.