Flexible Thermocamouflage Materials in Supersonic Flowfields with Selective Energy Dissipation.

Camouflage refers to a creature's behavior to protect itself from predators by assimilating its signature with the environment. In particular, thermal camouflage materials in the infrared (IR) wave are attracting interest for energy, military, and space applications. To date, several types of camouflage materials such as photonic crystals and metal-dielectric-metal structures have been developed. However, flexible camouflage materials still face challenging issues because of the material's brittleness and anomalous dispersion. Herein, we propose flexible thermocamouflage materials (FTCM) for IR camouflage on an arbitrary surface without mechanical failure. Without using a polymer as a dielectric layer, we realized FTCM by changing the unit cell structure discretely. By imaging methods, we verified their flexibility, machinability, and IR camouflage performance. We also measured and calculated the spectral emissivity of FTCM; they showed electromagnetic behavior similar to a conventional emitter. We quantified the IR camouflage performance of FTCM that the emissivity in the undetected band (5-8 μm) is 0.27 and the emissivity values in detected bands are 0.12 (3-5 μm) and 0.16 (8-14 μm) in the detected bands, respectively. Finally, we confirmed the IR camouflage performance on an arbitrary surface in a supersonic flowfield. FTCM are expected to help to improve our basic understanding of metamaterials and find widespread application as IR camouflage materials.