Tuneable multicoloured patterns from photonic cross-communication between cholesteric liquid crystal droplets

Monodisperse droplets of planar-aligned cholesteric (N*) liquid crystal exhibit an intriguing capacity for photonic cross-communication, giving rise to colourful patterns that depend sensitively on the N* pitch, droplet positions and illuminated area. The phenomenon results from a combination of omnidirectional selective reflection of N* droplets-which thus act as spherically symmetric self-assembled photonic crystals-and total internal reflection at the continuous phase surface. We outline how the unique optical properties can be employed in numerous applications.