Porous Nanostructured Composite Film for Visible-to-Infrared Camouflage with Thermal Management.

Progressive advancement in modern detection technologies entails multispectral compatible camouflage. Previously, infrared camouflage materials, such as photonic crystals and metamaterials, have been developed, but improved multispectral compatibility, easy fabrication, and cost-effectiveness remain a challenge. Here, we report a nanostructured composite film based on oxalate-rich porous alumina (OPA) for visible-to-infrared compatible camouflage and simultaneous thermal management. The nanostructured composite film consists of a visible-transparent OPA layer, a composite layer of OPA/metal oxides, and an aluminum substrate. Each functional layer exhibits desirable reflection/emission properties for infrared and visible camouflage. Infrared camouflage is realized by the high reflection (low emission) of the metal substrate in both infrared-detected bands (3-5 and 8-14 μm). Meanwhile, radiative cooling arising from the intrinsic absorption of oxalate in the undetected band (5-8 μm) enhances surface heat dissipation. In addition, background-matching colors can be tuned by the metal oxides in the composite layer for visible camouflage, such as green for forest and brown for desert. This work provides a facile strategy to modulate multispectral absorption/emission properties with much flexibility and thus has great potential for energy conversion and stealth applications.