Structural color refers to coloration in materials that is not caused by pigments or dyes but is instead a result of the physical structure of the material. In structural color, the interaction of light with the microscopic or nanoscopic structure of the material produces color through interference, diffraction, or other optical effects. This is in contrast to pigments, which achieve color by selectively absorbing certain wavelengths of light.
Key characteristics of structural color include:
Microscopic/nanoscopic structure: The coloration is due to the specific arrangement of structures at a microscopic or nanoscopic scale within the material. These structures are typically on the order of the wavelength of visible light.
Interference and diffraction: Structural color often involves interference or diffraction of light waves as they interact with the periodic structures in the material. This interaction results in certain wavelengths reinforcing each other (constructive interference) and others canceling out (destructive interference), producing a specific color.
Angle dependence: The perceived color may change with the viewing angle due to the interference or diffraction effects. This angle dependence is a characteristic feature of many structural color phenomena.
No pigments or dyes: Unlike traditional coloration, which relies on pigments or dyes that absorb specific colors of light, structural color does not involve the absorption of light by pigments. Instead, it relies on the manipulation of light through the material's structure.
Examples of structural color in nature include the vibrant colors of certain butterfly wings, bird feathers, and iridescent beetles. These organisms achieve their coloration through the microscopic or nanoscopic structures present in their tissues rather than through pigments.
Artificially engineered structural color is also an area of scientific research and technological development. Researchers and engineers have designed materials with nanostructures to produce specific colors without the use of pigments, leading to potential applications in displays, sensors, and coatings.
Overall, structural color provides an alternative approach to achieving vivid and iridescent colors in both natural and engineered materials by leveraging the principles of optics and wave interference.