Polymer Bragg stack as color tunable photonic paperElectronic supplementary information (ESI) available: FTIR spectra of the polymer films. See DOI: 10.1039/c2jm15943k

Polymer 1D photonic crystals with perfect optical tuning and distinctive brilliant colors are successfully fabricated through alternating thin films of PMMA and PNIPAM- co -PGMA, which can be easily processed as photonic paper by combining with top-down assisted photolithograph. The photonic paper is prewritten by ultraviolet light cross-linking with a photo mask and read with water as ink. The writing and erasing process is smoothly reversible by repeatedly exposing the material to water and air. The color of letters written on the paper can be modulated by tuning the cross-linking density and ink temperature. Moreover, multicolors can be integrated onto the photonic paper simultaneously by making the degree of cross-linking of different regions of the photonic paper different. The fabrication method is simple and low-cost, and the photonic paper can be easily manufactured in large areas. The integrated multicolor and its diverse change with external stimuli promises the photonic paper lots of potential applications, such as colorful sensors, security labels, full-color printing, displays and so on. A facile method to fabricate polymer Bragg stack photonic paper by selectively cross-linking the polymer multilayer film through UV irradiation is reported. Versatility in pattern generation, color tuning and integrating different colors together can be easily achieved in this photonic system.