Temperature-Programmable Ultrathin Flexible and Brilliant-Colored 1D Photonic Crystal Films for Photonic Pigments and Sensing

1D photonic crystals (1DPCs) with bright structural colors are important in a variety of applications, such as sensing, bioimaging, and smart displays. However, the lack of methodologies to produce self-standing 1DPCs remains a challenge for their practical application. Here, we report a method for fabricating ultrathin flexible and brilliantly colored 1DPC films based on the temperature-programmable film-forming property of polymer nanoparticles. Nano poly(styrene-acrylic acid) (P(St-AA)) and TiO2 are used for 1DPC assembly to achieve high reflectivity and brilliancy. Based on the change of heating temperature and the microbubbles produced during dissolving of the SiO2 sacrificial layer, the size of the self-standing PCs can be facilely regulated, and the layer-by-layer microstructure remains unchanged. When heated at 85 °C, 1DPC fragments with various brilliant colors are prepared, and they can maintain brilliant structural color for more than one year, which is the first report using 1DPCs as photonic pigments. When heated at 200 °C, the whole 1DPC film can be released from the substrate and retains its mechanical integrity. With this designed method, an ultrathin dry self-standing 1DPC film with a thickness of only 557 nm is first obtained. The self-standing 1DPC films can be patterned easily and transferred to any surfaces such as curved glass bottles and flexible textile fabrics. Moreover, this method will not affect the response of PCs to benzene vapor, which provides a platform for a wearable sensor.