Gradient‐Impedance‐Regulated Multispectral Metamaterial: Broadband Microwave Low Scattering and Infrared Information Encryption

ABSTRACT The radiative properties of macroscopic devices are dominated by the intrinsic characteristics of metamaterials and the dimension of their primitives, paving the way for promising applications in multispectral compatible camouflage. In this work, we propose a layered metamaterial via the integration of a porous microwave‐absorbing metamaterial and an infrared‐stealth metasurface. This design achieves ultra‐broadband microwave absorption and low infrared emissivity. The design strategy adopts a carbonyl iron particle (CIP)/polyurethane (PU) composite as the microwave‐absorbing coating: patterning a porous structure enables the fabrication of a polarization‐insensitive metamaterial with broadband absorption. Furthermore, hierarchical coatings with gradient mass fractions optimize impedance matching, whereas a performance‐optimized infrared shielding layer guarantees excellent multispectral compatibility. Theoretical and experimental investigations clarify the microwave absorption mechanism and structural focusing behavior of the proposed metamaterial. The fabricated multiscale hierarchical metamaterial exhibits an ultra‐wide effective absorption bandwidth (4.7–18 GHz), low infrared emissivity (<0.3), and outstanding environmental stability, as corroborated by both simulations and experiments. Notably, this metamaterial also demonstrates great potential in thermal imaging information encryption. These results provide a novel strategy for the design of multi‐band compatible camouflage devices.