One source of the biological inspiration of the research – a Gooty Sapphire Ornamental tarantula (credit: Cathy Keifer, Dreamstime.com)A biomimetic research project has developed a new approach to producing structurally colored materials inspired by the vibrant iridescent hair of blue tarantulas. A team from the University of Akron, with colleagues from Ghent University, Karlsruhe Institute of Technology and the University of Nebraska-Lincoln, came up with a technique that shows consistent color from every viewing direction and which could lead to the scaling up and manufacture of such colors to replace pigments and dyes.
Structural colors are more vibrant and durable than the pigments used in most human-made products, and are produced through optical effects when light interacts with nanostructures around the same size as the wavelength of light. However, most structural colors are very iridescent, changing color when seen from different angles. This has benefits for anti-counterfeiting and security applications but is undesirable when used for screen displays or wall paint, for example.
Initially interested in using the principles of structural color to develop a colorant to replace pigments and dyes, they carried out a range of experiments to understand the best way to produce non-iridescent structural colors where the hue remains the same regardless of the viewing direction. They investigated nature for biological models that could help solve this challenge, finding there were many non-iridescent blue tarantulas.
In the study, as reported in the journal Advanced Optical Materials [Hsiung et al. Adv. Opt. Mater. (2017) DOI: 10.1002/adom.201600599], the researchers demonstrated that the hairs of some blue tarantulas had a flower-like shape that reduced the iridescent effect resulting from periodic structures. They tested this hypothesis with computer simulation and physical prototypes developed using specialized nano-3D printing technology, producing a color that offers a viewing angle of 160o, the largest viewing angle of any synthetic structural colors, overturning the belief that long-range order photonic structures are always iridescent.
“We are the first to demonstrate that non-iridescent structural colors can be produced by highly ordered and periodic photonic structures, as long as the structure is hierarchical, and most importantly with high degrees of rotational symmetries”Bill Hsiung
As lead author Bill Hsiung points out, “We are the first to demonstrate that non-iridescent structural colors can be produced by highly ordered and periodic photonic structures, as long as the structure is hierarchical, and most importantly with high degrees of rotational symmetries”.
The team now hopes to demonstrate their proposed non-iridescent structural colored material could be manufactured in an economically viable way using existing fabrication technologies. As well as in dyes and creating color for wide-angle viewing systems in devices such as mobile phones and televisions, the breakthrough could find applications in industries where color is the main feature of products, such as textiles, cosmetics, fashion and packaging.