Tsukuba, Japan (PRWEB UK) 11 January 2012
A recent paper, — published in Science and Technology of Advanced Materials (STAM) — focuses on 'structural color'. The striking colors of butterfly wings and peacock feathers are examples of so-called ‘structural color’ in nature. You see these colors due to the strong reflection of certain wavelengths of light from the birds’ feathers. Nature’s ability to actively control color has led scientists to integrate structural color into the design of critical modern technologies such as low power displays and optical filters.
But how do scientists accurately mimic nature for such applications?
Hiroshi Fudouzi at National Institute for Materials Science (NIMS) in Japan describes the challenges facing materials scientists for the realization of photonic crystals based on design of bioinspired structural color.
Tunable structural color in nature
The physical mechanisms and role of refractive index can be considered by looking at the South American tropical fish known as ‘Neon Tetra’ which capable of changing color from green in the daytime to violet-blue at night.
Bioinspired materials for tunable structural materials
Mathematical models describe the reflection of light from 1D multilayers and 3D colloidal crystals. Specific examples include layer-by-layer synthesis of polymer-based Bragg reflectors; electrochemical tunable color of block copolymers between red and green; and stress/stain induced changes in the color hydrogel membrane from red to blue.
3D colloidal crystals and tunable structural color in opal composites
Opal is an example of a 3D photonic crystal with well understood diffraction properties. This section focuses on synthetic opal structures synthesized using 3D nanostructures of monodispersed polystyrene particles on silicon substrates; a highly stable new soft material consisting of a colloidal crystal embedded in a poly(N-isopropylacrylamide) hydrogel whose diffracted wavelength is thermally tunable across the entire visible spectrum; and recent reports on tuning the color of hydrogels by magnetic fields.
Technology using ‘bioinspired approaches’ already exist. Examples include a 3D opal photonic crystal- humidity sensor—color changes from blue to red at high humidity—based on nanoporous structure of the Hercules beetle. A high-performance optical gas sensor with a highly selective response based on Morpho butterfly wings and new, more complex materials design such gyroid and related phases.
 Hiroshi Fudouzi, ‘Tunable structural color in organisms and photonic materials for design of bioinspired materials’, Science and Technology of Advanced Materials 12 (2011) doi:10.1088/1468-6996/12/6/064704 Review paper in the focus issue on New Materials Mimicking Nature.
Affiliation: Photonic Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
PICTURES - full resolution pictures with captions may be found in the attached word document.
National Institute for Materials Science, Tsukuba, Japan