Structural colour materials and methods for their manufacture

A composite material has a periodic arrangement of particles distributed in a matrix. The refractive index of the material of the particles is different to the refractive index of the material of the matrix and the periodicity is such that, when illuminated with white light, the periodic arrangement provides structural colour. A method of manufacturing the material includes the steps of: (i) forming the periodic arrangement by applying an electric field across a distribution of the particles in a curable liquid; and (ii) curing the curable liquid to form the matrix and thereby fixing the periodic arrangement of the particles. Also disclosed is a structural colour printing system suitable for carrying out the method of manufacture of the material