Revealing invisible photonic printing: colorful pattern shown by water

Patterning and displaying of photonic crystals are critical for building advanced photonic materials. We developed a monolayered colloidal crystal (MCC) based photonic material through a mask-assistant photo-polymerization process. Polystyrene (PS) nanoparticles were firstly assembled on the glass slide to form highly ordered MCC, this template is invisible and could diffract visible light when infiltrated by solvent. This reversibly displaying property was successfully maintained after the MCC was surrounding by a polymer layer via photo-polymerization, meanwhile a pattern could also be printed on the polymer with the help of a mask. Such photonic printing could be reversibly shown and hidden, revealing the colorful pattern was mainly due to the non-uniform cross-linking density of the polymer.