Mimicking the properties of the wings of a South American butterfly could in future reduce the amount of light reflected from our smartphone displays and computer screens.
Greta Oro, or glasswing, is the name of a butterfly that possesses extraordinary properties, which are now being studied at the Karlsruhe Institute of Technology (KIT) in Germany. What makes this species of lepidoptera so different from others is the extreme anti-reflective properties of its wings. The wings are almost transparent, and consequently they reflect back hardly any light, which makes it almost impossible for predators to track them down. This transparency property is due to the structure of the butterfly’s wings, which the KIT researchers have been working to model.
When the Karlsruhe team studied the butterfly’s wings they observed an architecture which had already been identified in previous studies on other animals: nanostructures in the form of pillars, which result in low levels of light reflection. However, what is different about Greta Oro is that its nanostructures are of random height – between 400 and 600 nanometers – and arranged irregularly, with the distance between the pillars ranging from 100 to 140 nanometers.
Under the microscope: the irregular nanostructures on the butterfly’s wings
The researchers mathematically modelled this irregularity in the nanostructures, and were able to prove that the low reflection at variable view angles is caused by this irregularity. KIT doctoral student Radwanul Hasan Siddique, who discovered this effect, explains that: ‟In contrast to other natural phenomena, where regularity is of top priority, the glasswing butterfly uses an apparent chaos to achieve effects that are also fascinating for us humans.”
As any user knows, smartphone, tablet and other types of device screens are highly reflective. So the unique properties of the glasswing could perhaps be harnessed to reduce glare on our display screens. Due to the structure of the butterfly’s wings, specular reflection varies between 2 and 5% depending on the angle of view. By contrast a flat glass plane reflects at least 8% and sometimes as much as 100% of the incoming light. In addition, the butterfly wing not only exhibits a low reflection rate of the light spectrum visible to humans, it also suppresses the infrared and ultraviolet radiation that can be perceived by animals. These are vital factors for the butterfly’s survival.
The KIT findings open up a range of potential applications on our electronic devices wherever low-reflection surfaces are needed – e.g. lenses as well as mobile phone displays. Moreover, prototyping experiments have already revealed that an irregular nanostructure surface coating also has water-repellent and self-cleaning properties. Drawing on all these findings, the Karlsruhe Institute research team is currently developing a prototype for a screen coating.