New Method for Structural Colors Production Using Melanin Nanoparticles

SpecialChem - October 6th, 2017
Scientists from The University of Akron, Northwestern University, and University of Ghent demonstrate a feasible solution for producing structural colors inspired by bird feathers. Their findings have been published on Science Advances, an open access online journal established by Science.

Structural Colors - Enable Creation of Nonfading Colors


Nature provides many spectacular examples of structural colors, such as duck wing feathers and wild turkey feathers. In continuation of their earlier research that unraveled the fundamental properties of melanin — a family of natural pigments found in skin, hair, eyes and the plumage of brightly colored birds — these examples served as bio-inspiration for the design of core-shell synthetic melanin nanoparticles for the production of bright structural colors.

Melanin – An Important Biomaterial

Melanin has been around for millions of years. “Melanin is an important biomaterial that has so far been underutilized in materials science and technological applications,” says UA’s Dr. Ali Dhinojwala, H.A. Morton Professor of Polymer Science and one of the principal investigators on the project.

In this most recent research, the team has found that tiny packets of synthetic melanin produce structural color when they are packed into semi-ordered spherical particles

Structural color occurs through the interaction of light with materials that have patterns on a sub-micron scale, which reflect light to make some wavelengths brighter and others darker

Full Spectrum of Colors Possible

“The chemistry we use to make these particles is based on the main ingredient that goes into making melanin,” notes Dhinojwala. “Then we take these melanin particles and self-assemble into a structure using a very straight forward process. It is similar to things we see in our homes, like mixing oil and water together creating emulsions. Those emulsions essentially allow us to assemble these particles into photonic inks which we call photonic supraballs.”

These supraballs could be directly added to paints, plastics, and coatings and also used as ultraviolet-resistant inks or cosmetics.

These nanoparticles were self-assembled using a one-pot reverse emulsion process, adds Ming Xiao, currently a postdoctoral research fellow. “It resulted in bright and non-iridescent supraballs. With the combination of only two ingredients, synthetic melanin and silica, we can generate a full spectrum of colors.”

“The use of melanin as the core material can increase the brightness and saturation of supraballs due to its unique combination of high RI and broadband absorption of lights. In addition, melanin is biocompatible and can dissipate almost 90% of the UV radiation into heat within a nanosecond, making those melanin-based supraballs suitable for cosmetics or UV-resistant inks.”

Source: The University of Akron
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