Geon Hwee Kim and Geunbae Lim from the department of mechanical engineering at Pohang University of Science and Technology, and Taechang An from the department of mechanical design engineering at Andong National University recently published their work in the American Chemical Society’s journal of Applied Materials & Interfaces. The Korean scientists’ research article is entitled, Bioinspired Structural Colors Fabricated with ZnO Quasi-Ordered Nanostructures.
In it, they outline how lab-fabricated zinc oxide nanostructures can replicate the structural color changing effect found in beetles.
"The shells, or exoskeletons, of beetles are covered with stacks of crystalline-like shapes that scatter light and produce dazzling colors,” explains the American Chemical Society in a media release about the newly published research.
The ACS goes on to note that “in some cases, these colors can change with just a slight shift of the viewing angle. Known as structural colors, scientists have long been interested in replicating them for use in paints, dyes, cosmetics and other products.”
Structural color, as synthesized in a lab, has been expensive to make and not very flexible. As the ACS describes it, “once they are attached to a surface, it is hard to modify them.”
These are the challenges that Kim, Lin, and An set out to address. And they certainly aren’t the first. Scientists at L’Oréal have been working at scalable structural color for some time, as this Cosmetics Design article from April notes. And another team of researchers boasted having found a commercially scalable way to mimic structural color in 2015, as discussed in this CD Buzz video news segment from Cosmetics Design.
Kim, Lin, and An have documented a “method [that] combines the advantages of top–down and bottom–up synthetic approaches in that the structural color can be continuously modified once fabricated,” the team explains in the article abstract.
Through hydrothermal growth, the team created zinc oxide nanostructures in water that was between 40 degrees Celsius and 80 degrees Celsius. It was, according to the ACS release, quick and easy. And, “the method also allowed them to better control the size and spacing of the nanostructures.”
In the abstract of their published article, Kim, Lin, and An explain further, writing, “this fabricated nanostructure has a thickness on the order of 103 nm and a diameter on the order of 102 nm. The thickness and diameter increase in proportion with the synthesis time….[and] the shape of the nanostructure can be easily tuned by simply adjusting the synthesis and etching times.”