Extruding opals: Self-assembling active soft nanophotonics on the kilometre scale

The authors concentrate on a new range of structural colour nanomaterials which can be mass produced as films on the kilometre scale. While most manmade (and natural) colours exploit dye absorption, there is strong interest in avoiding these carcinogenic and UV-bleached chemicals. Alternative structural colours are produced from periodic wavelength-scale-sized transparent components, and thus are benign, longlived, and possess new optical features. The authors create polymer photonics crystals made of cross-linked polymer spheres dispersed in a soft elastomeric matrix, using a novel industrially-scalable shear-based nano-assembly. Simply tuning the size of the spheres changes the colour across the entire visible spectrum, while optimised shearing creates single-domain opal films. The authors demonstrate a wide variety of new optical properties based on the resonant scattering phenomena.