A Moth’s-eye Strategy to Eliminate Screen Glare

Thank the mundane moth for inspiring a new antireflection film that enhances the readability of smart phone and tablet screens in bright sunlight. The coating developed by University of Central Florida researchers is modeled after the nanostructures found on moth eyes.

The antireflection film, which is also scratch-resistant and self-cleaning, exhibits a surface reflection of just 0.23 percent, much lower than the iPhone’s surface reflection of 4.4 percent. Tiny dimples, each about 100 nm in diameter, cover the material.

Smart phones currently use a sensor to detect bright ambient light and then boost the screen’s brightness level to overcome the strong surface reflection. This improves readability but also drains battery power.

The researchers took a nature-based approach to this problem, focusing on the antireflective nanostructuresResearchers created a film of moth-eye-like nanostructures to improve the sunlight visibility of screens on mobile phones and tablets. (Image Credit: Shin-Tson Wu, College of Optics and Photonics, University of Central Florida) that cover the eyes of moths, allowing them to see in the dark and preventing eye reflections that might attract predators. Moth-eye-like nanostructures have been used by other researchers to reduce the sunlight reflected off the surface of solar cells.

A high-resolution, high-precision fabrication technique was developed that uses self-assembled nanospheres to form a precise template. The latter can be used to create the moth-eye-like structure on a coating, and the simplicity of this process allowed fabrication of the intricate structure in a film large enough to apply to a mobile screen.

A computational model devised to simulate the optical behavior of the coatings accurately represented experimental results and was applied to optimize the size of the moth-eye nanostructures to achieve the best performance.

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 are now working to further improve the film’s mechanical properties, including finding the best balance of surface hardness and flexibility to make the surface rugged enough for long-term use on touch screens.