Four‐State Photonic Crystal Device with Temperature and Ultraviolet Light Sensitivities

Abstract Responsive photonic crystals have garnered significant attention in recent years due to their remarkable capability of exhibiting dynamic color changes in response to external stimuli. Herein, a novel multistage anti‐counterfeiting photonic crystal device that integrates chemical (luminescent material) and physical (photonic crystal structure) elements is reported. Based on photochromic materials and thermochromic capsules, a four‐state thermochromic/photochromic photonic crystal (TPPC) composite film with dual responsiveness is developed through in situ emulsion polymerization and a straightforward roll shear technology. This innovative approach successfully resolved the issue of short‐range order and long‐range disorder in conventional photonic crystal films. Through the integration of a multilayer structure and a mask plate process, the dual effects of photochromic and thermochromic are seamlessly combined, enabling the film to exhibit four different optical states under the combined stimuli of temperature and UV light. Unlike tristate systems, the film integrates dual stimuli (UV + heat) for enhanced complexity. Notably, the film demonstrates multilevel responsiveness and dynamic decorative capabilities, allowing flexible switching between four optical states. Furthermore, the TPPC film boasts excellent mechanical properties (with a tensile strength exceeding 2 MPa), emphasizing its strong potential for applications in anti‐counterfeiting, information encryption, and dynamic display technologies.