Tunable reflectance of an inverse opal–chiral nematic liquid crystal multilayer device by electric- or thermal-control

A new type of electric- or thermal-responsive multilayer device composed of SiO2 bilayer inverse opal (IOP) and chiral nematic liquid crystals (N*LCs) was developed. Bilayer IOP was fabricated by layer-by-layer assembly of polystyrene (PS) spheres with two different sizes and showed a reflectance in an extended range of the near-infrared region. Furthermore, the electrically or thermally tunable reflectance of the bilayer-IOP–N*LC device was investigated. The device exhibited the photonic bandgap (PBG) of the N*LC–IOP composite structure with the application of an electric field (voltage-on), while it presented the reflectance of N*LCs without an electric field (voltage-off) and the electrically-responsive behaviour could be reversibly switched. Besides, the device exhibited a gradient redshift of reflectance as temperature increased below the clearing point (TC) while it showed the PBG of the N*LC–IOP composite structure when the temperature was above TC.