An anti-reflective coating inspired by compound lenses in moth eyes. Source: WikipediaAn anti-reflective coating inspired by the compound lenses in moth eyes could help boost solar cell efficiency and sharpen the view of image sensors. Researchers in Singapore have developed a nanoscale pattern stamping method that could make manufacturing such coatings easier. The news was reported in Scientific American.

Nocturnal moths navigate in low-light conditions thanks to their eyes which are made of arrays of microsized lenses patterned with dome-shaped nanostructures. This design reduces reflection and also prevents water from beading up on the creatures' eyes. Re-creating this design in the lab, either by using moth eyes as tiny stamps or by plasma etching, has proved laborious.

Raut and Mohammad S. M. Saifullah from the Agency for Science, Technology & Research in Singapore turned to nanoimprint lithography—a method for stamping high-resolution, nanoscale patterns over large areas. To create a reusable stamp, they made two sets of nickel molds to pattern films of polycarbonate; one with 200-nanometer diameter domes and another with microlenses of 2 to 25 micrometer in diameter. First, they stamped the nanodomes and protected that pattern by spinning a thin coating of a sacrificial polymer on top. Second, they stamped the larger microlenses. Finally, they washed away the polymer, leaving a polycarbonate microlens array.

The moth-inspired arrays reflected 4.8% of light, compared with 8.7% typically reflected by simple microlenses. When the researchers varied the incident angle of light, the arrays continued to perform roughly twice as well. These nanodomes also repelled water.

Researchers say they are currently adapting the imprinting technique to a roller printer that should be able to pattern larger areas at high speeds.