Transparent and iridescent photonic films with intelligent responsive ability based on electrospun core-shell nanofibrous membranes

The fabrication of transparent and iridescent photonic films that possess intelligent responsiveness by membrane electrospinning is challenging due to the lack of periodic changes in the refractive index (RI) of electrospun membranes. Herein, transparent and iridescent photonic films are prepared through electrospinning core-shell polyacrylonitrile/glucose-containing polyvinyl alcohol (PAN/PVA@GLU) membranes, infiltrated with a cellulose nanocrystal/polyvinyl alcohol/glucose (CNC/PVA/GLU) suspension, followed by evaporation-induced co-assembling. The as-prepared transparent and iridescent photonic films exhibited reversible changes in selective reflection wavelengths ranging from the visible light to the near-infrared region in response to alternate changes in the relative humidity (RH). Thus, the films could be used as an alcohol dipstick by choosing solvents with different polarities such as alcohol-water mixtures of different ratios. Moreover, the films were highly deformable with a strain at failure up to 14.91% without a compromise of strength. In sum, the current work demonstrates a strategy for the design and fabrication of transparent and iridescent photonic films with intelligent responsiveness using electrospinning, and a soft material platform for developing scalable colorimetric sensors and optically active components.