Hierarchical Metamaterials for Multispectral Camouflage of Infrared and Microwaves

TLDR

Metamaterials enable camouflage by manipulating electromagnetic radiation, but most studies focus on single‑band performance, while multispectral camouflage is difficult due to the large disparity in unit‑cell dimensions. The authors aim to demonstrate hierarchical metamaterials that control multiple spectral bands by converting absorbed microwave energy into selective infrared emission. They integrate an infrared selective emitter with a microwave selective absorber in a large‑unit‑cell structure up to 10 cm, enabling simultaneous control of microwave absorption and infrared emission. The hierarchical metamaterial increases emissive power in the 5–8 µm band by 1570 % relative to gold, suppresses thermal instability, and reduces infrared (8–12 µm) and microwave (2.5–3.8 cm) signatures by up to 95 % and 99 % respectively.

Abstract

Abstract Camouflage is an emerging application of metamaterials owing to their exotic electromagnetic radiative properties. Based on the use of a selective emitter and an absorber as the metamaterials, most reported articles have suggested the use of single‐band camouflage, however, multispectral camouflage is a challenging issue owing to a difference of several orders of magnitude in the unit cell structure. Herein, hierarchical metamaterials (HMMs) for multispectral signal control when dissipating the absorbed energy of microwaves through the selective emission of infrared (IR) waves from the unit cell structure of the HMM are demonstrated. Integrating an IR selective emitter (IRE) with a microwave selective absorber, multispectral signal control with the large‐sized unit cell structures of up to 10 cm are realized. With an IRE, the emissive power from the HMM toward 5–8 µm is 1570% higher than the Au surface, which is preventing the occurrence of thermal instability. Furthermore, we determine that the signature levels of targeted IR waves (8–12 µm) and microwaves (2.5–3.8 cm) are reduced by up to 95% and 99%, respectively, when applying the HMM.