Thermal-Responsive Photonic Crystal with Function of Color Switch Based on Thermochromic System

Responsive photonic crystals have attracted considerable attention. The responsiveness is usually achieved through the variation of reflection wavelengths based on Bragg diffraction. However, distinguishing external stimuli from intrinsic angle dependence is a challenge. Herein, a novel thermal-responsive photonic crystal was constructed based on the synergistic effect of the low-angle dependence of SnO₂ inverse opals and a thermochromic phase change system. The organic thermochromic phase change system was obtained by mixing the fluoran dye (heat-sensitive red TF-R₂), bisphenol A, and aliphatic alcohols in a certain proportion. By filling the thermochromic phase change system into SnO₂ inverse opals, the thermal-responsive photonic crystal was fabricated. Through simple external thermal stimulation, the mutual transformation of low-angle-dependent structural color and pigmentary color is realized and inverse opal patterns can be displayed and hidden. The proposed system, while preventing the interference of the observation angle to the thermal stimulation, shows potential application prospect in the fields of anti-counterfeiting and information encryption fields.