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 (T_C) while it showed the PBG of the N∗LC-IOP composite structure when the temperature was above T_C.