posted on 2021-08-12, 13:14authored byZiying Hu, Nathan P. Bradshaw, Bram Vanthournout, Chris Forman, Karthikeyan Gnanasekaran, Matthew P. Thompson, Paul Smeets, Ali Dhinojwala, Matthew D. Shawkey, Mark C. Hersam, Nathan C. Gianneschi
Melanin
is a natural pigment with a high refractive index and strong
light absorption across the visible spectrum, making it an ideal material
for producing structural colors. Here, we report non-iridescent structural
color control via inkjet printing of self-assembled
synthetic melanin nanoparticles (SMNPs). Adding silica shells to SMNPs
allows for further tuning of both the hue and brightness of the resulting
structural colors. The peak wavelengths show a linear dependence with
the diameter of the nanoparticles, allowing correlation between ink
composition and structural color using the Bragg–Snell law.
Additionally, mixtures of SMNPs of different sizes result in colors
with peak wavelengths that vary linearly with the mixing ratio in
the ink, leading to diverse and predictable colors from one type of
material. The morphology of the self-assembled SMNP structures is
further controlled by the hydrophilicity of the substrate, providing
another means for tailoring the structure and properties. Since structural
colors are less susceptible to degradation than organic dyes, this
work has implications for emerging sensing, display, and security
applications.