3D Printing Reveals Nanostructures That Create Color in the Blue Tarantula

The blue tarantula (Poecilotheria metallica) inspired researchers to produce non-iridescent structural colors. Credit: Tom Patterson

The search for new ways to create color is as old as mankind. The quest to create additions to the palette that would expand art and design beyond the whites, blacks, and browns most easily available has taken humanity down some odd pathways. For example, people dedicated significant amounts of time and resources towards extracting an excretion from the hermaphroditic murex snail that allowed them to create a range of purples and blues. Happily for the murex snail community, 10 to 12 thousand of which were required to produce a single gram of dye, there are now alternative ways to produce a whole range of these hues.

The story of modern pigments is the story of chemicals. Dow and Bayer both started their lives producing dyes and as synthetic dyes became more sophisticated, the leaders in fashion were determined by the brightest, boldest colors. Unfortunately, many of the chemicals required to create these dyes are extremely toxic and contribute to environmental degradation. Animals such as the peacock, however, manage to present the most dazzling array of colors, all without using a single drop of pigment.

The 3D print of the optimized flower structure is only 15 µm in dimension. A human hair is about three times as thick. Credit: Bill Hsiung, Universtiy of Akron

This method of creating color has been of interest for some time, but it is only with the development of 3D printing technology that it appears to be moving within the realm of reality. Imagine a pair of jeans that could be blue without the use of damaging pigments or dyes, but just as a result of their structure? Unfortunately, it’s not as easy as it might have sounded as many of these kinds of structures cause iridescence, meaning that the color perceived is dependent upon the angle at which it is viewed. That makes it cool for painting cars, but not so great for regular applications.

The synthetically generated flower structure inspired by the blue tarantula reflects light in the same color over a viewing angle of 160 degrees. Credit: Derek Miller

Enter the strikingly beautiful poecilotheria metallica, a type of tarantula that boasts a stunning blue coat. Given that this is an enormous spider, known to be aggressive and possessing a highly toxic venom, it might have previously been outside your idea of the beautiful. He wears his blue coat not because of an accident with a dye vat but because of a built-in nanostructure that causes that color to be the only reflected. All this with no damage to the environment…just a case of willies for arachnaphobes.

What is unusual about the cobalt tarantula’s color has been discovered by Radwanul Hasan Siddique, a researcher at the Karlsruhe Institute of Technology (KIT), in collaboration with international colleagues is that the color present in the tarantula does not exhibit iridescence. This is due to the unique nature of their nanostructure: flower-like and multi-layered. Variations in the size of the ‘flower’ cause the appearance of different colors, unchanging over a viewing angle of 160 degrees. Siddique, who published the results of his work in the Journal of Advanced Optical Materials, has explained his hope for this discovery:

“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.”

The ability to easily 3D print on this nanoscale brings this dream one step closer to everyday reality and could even impact the need for colored filaments. The enormous contribution began with an enormous spider and, while I’m not ready to give him a hug to say thanks, I can at least appreciate from a distance what the tarantula might eventually do for humankind. Discuss in the 3D Printed Nanostructures forum at 3DPB.com.