Nov 24, 2016 | By Nick

A team of researchers at the Karlsruhe Institute of Technology has found a way to replicate the "structural colors" of blue tarantulas and peacocks using overlapping, 3D printed nanostructures that bend light to create dynamic color effects. The technology could eventually help to replace toxic pigments in packaging, industrial applications, and even cosmetics.

Structural coloration, different to pigment coloration, is the production of color through microscopically "structured" surfaces that interfere with natural light. Peacock feathers, for example, are actually of a brown pigment, but the patterns in their fine ridges make them reflect vivid blue and green. When produced using a new 3D printing method, structural colors appear more vibrant and last longer than traditional pigments, while also having the advantage of non-toxicity.

One fascinating yet often undesirable effect of structural colors is their ability to change hue and iridescence depending on the viewing angle, as with the underside of a CD. Manufacturers have frequently sought to minimize this effect in order to produce fixed colors, often unsuccessfully. In nature, however, the notoriously aggressive blue tarantula (as well as more sedate peacocks and kingfishers) can manage that feat effortlessly, and their incredible physiology has helped a group of Karlsruhe researchers to understand the secret to fixed structural colors. The researchers concentrated on the tarantula, and found that hairs on its body formed flower-like, multi-layered structures.

The team analyzed the reflective behavior of the spider’s structural color, before replicating the hairs with a nanoscale 3D printer. Not content to simply copy the blue tarantula’s color, however, Radwunal Hasan Siddique's team also wanted to find a 3D printable solution that could be made commercially viable across the whole color spectrum. Working with teams in Belgium and the USA, the scientists at KIT refined a model for producing any chosen structural color that is consistent through a viewing angle of 160 degrees. That’s the biggest viewing angle ever achieved with a synthetic color, and its flower-like structure, inspired by the blue tarantula, is now potentially commercially viable.

By changing the dimensions of the flower-like structure, which measures just 15µm across, the researchers found they were able to change the color at will. This is a big step in the world of material and color science, and could change the world of textiles and packaging. In the long run, it could even have a major impact on the cosmetics industry, although that is some way off. “This could be a key first step towards a future where structural colorants replace the toxic pigments currently used in textile, packaging, and cosmetic industries," said Siddique.

Now that the researchers have a workable model, there is still one major issue that means we’re not going to see structural color taking over just yet. Right now, there are just a handful of companies and institutions in the world that offer nanoscale 3D printing. KIT’s Dr Hendrick Holscher concedes that they couldn’t possibly service the potential demand for commercial applications, and even if they could, it simply wouldn't be cost effective right now.

Luckily, with the 3D printing industry moving so fast, the team sees the relative shortage of nanoscale 3D printing equipment as a temporary hurdle. Nanoscale 3D printing was a dream not so long ago, but now the likes of the US Department of Energy’s Oak Ridge laboratory are working on Focused Electron Beam Induced Deposition printing, Harvard University has the Center for Nanoscale Systems, and leading companies and universities around the world are working on their own solutions. It’s therefore a matter of when, not if, we get a commercially viable solution for nanoscale 3D printing, and this method of applying structural color is just waiting for technology to catch up.

According to the researchers, another potential solution for structural color is to create amorphous nanoscale structures, which could alter the refraction of the light depending on the viewing angle. It’s an intriguing prospect for the future, when the 3D printing industry can produce individual, nanoscale prints at a commercially acceptable price point. At the moment though, the team at KIT firmly believes that the flower-like structure derived from the blue tarantula offers the most cost-effective and feasible model for the commercial application of structural color.

So, even if you’re afraid of spiders, give a moment of thanks for the blue tarantula, as it could help us build a bright, colorful, vibrant world with the nanoscale 3D printers that are just around the corner.



Posted in 3D Printing Application



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