Researchers at ETH Zurich have developed a full spectrum of colors by 3D printing artificially colored nanostructures, inspired by those of a butterfly.

Butterfly Cynandra opis is native to tropical Africa. The wings of the species are characterized by their brilliant colors. These colors are produced by complex surface structures in the size range of wavelength harnessed from visible light. By deflecting and refracting light rays, surface structures on the wings of the Cynandra opis either amplify or cancel out individual color components of the light, which results in a gemstone- esque shine.

Led by Andrew DeMello, the researchers of Biochemical Engineering, were able to replicate the naturally occurring structures of Cynandra opis using nano-3D printing. The outcome of the project resulted in a new easy-to-use principle that could be utilized for the production of structures that generates structural colors.

The leading author of the research, Xiaobao Cao explains, “The regular nanostructures on the wings of Cynandra opis were particularly well suited to reconstruction using 3D printing.”

Copying butterfly wings for the entire color palette

The wings of the Cynandra opis are composed of a two-dimensional grid of layers stacked on top of each other. The lattice spacing between these layers is between 0.5-1 micrometer.

The ETH researchers were able to produce 3D printed identical structures by varying the spacing and height between 250 nanometers and 1.2 micrometers. They discovered that it was possible to generate all the colors on the visible spectrum.

Many of the colors produced in the research were not recorded from the initial observations of the natural structure of the butterfly.

The 3D printed nanostructures were produced by using different materials, including a transparent polymer. “This made it possible to illuminate the structure from behind to bring out the color. This is the first time we’ve managed to produce all the colors of the visible spectrum as structural colors in a translucent material, explains Stavros Stavrakis, co-author of the study.

Where the technology can be used?

In an attempt to find the use of their technology, the researchers 3D printed a miniature image, made of structural color pixels measuring 2 by 2 micrometers.

According to the researchers, similar tiny images could be utilized in many industries for the authentication purposes such as banknotes and other documents.

Since the colors can be 3D printed using transparent materials, it’s also possible to manufacture color filters for optical technologies. This particular application fits well with the main research activity of deMello’s group, which develops microfluidic systems- miniaturized systems for chemical and biological experiments.

The researchers state that the large-scale production of nanostructures is also possible. That means it’s suitable for the manufacture of high-resolution color displays, such as flexible screens.

And finally, the researchers point out that structural colors could be an adequate alternative to the pigments used in printing and painting. The advantage of structural colors is that they last longer due to resistance to UV- induced fading and in most cases, they have a better environmental footprint.

Further details of the study can be found in the paper titled ‘Replicating the Cynandra opis Butterfly’s Structural Color for Bioinspired Bigrating Color Filters’.