Structural Coloured Surfaces
Colouring in nature mostly comes from the inherent colours of materials, but it sometimes has a purely physical origin, such as diffraction or interference of light. Some natural occurring structural colours originate from optical processes represented by thin-film interference, multilayer interference, a diffraction grating effect, photonic crystals, light scattering, and so on. An example of such natural structural colour is butterfly wings, which have been widely studied and artificially reproduced through modern nanofabrication techniques. The size of the unit cells of such passive diffractive elements is in the order of the wavelength of light usually in the sub micro meter range. Structural colours have attracted great interest because their applications have been rapidly progressing in many fields related to vision, such as the security printing, automobile, cosmetics, and textile industries. We provide tailored physical structural coloured surfaces which could provide true colour when viewed at a particular angle.