Reversible Optical Control Film Using Hydrogel-Perfluoropolyether Double-Layered Structures

초록

Recent efforts to mimic diverse micro/nanostructures found in nature have enabled the development of functional surfaces that can dynamically modulate optical properties in response to external stimuli. However, conventional single-material-based fabrication techniques have limitations in simultaneously implementing structural optical properties and stimulus responsiveness. In this paper, we propose a fabrication method for tunable optical control surfaces by laminating a hydrophilic hydrogel onto optical nanostructures. We fabricated 1000 nm-sized nanostructures exhibiting structural color in the visible wavelength range using conventional microelectromechanical systems (MEMS) and soft lithography processes. The hydrogel was applied over the nanostructured surface to form a double layer by copolymerization using a partial curing method. We fabricated a double-layered hydrogel-perfluoropolyether (PFPE) (DHP) film that exhibited structural color in dry conditions while becoming transparent under wet conditions. Optical properties were analyzed through the grating equation for light reflection and diffraction under dry and wet conditions. The DHP showed structural robustness and reliability of the optical properties. Finally, we demonstrate the potential applications of reversible optical control films for moisture-responsive encryption.

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