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

Abstract

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.

Easy-to-Manufacture In-Line 2D Nano Antenna for Enhanced Radiation-Cooled IR Camouflage

“…The manufactured nano antenna was well engineered with W 1 of 551 nm, W 4 of 673 nm, and T d of 100 nm showing a dimensional deviation of ∼20 nm (Figure e,f). The measurement results indicated that the manufactured PSO nano antenna was far superior to the previous reports. ,, In particular, it had broadband emission at 5–8 μm (ε̅ = 0.34), while simultaneously ensured low emission at 3–5 μm (ε̅ = 0.04) and 8–14 μm (ε̅ = 0.02) at a surface temperature of 300 K, which demonstrated good agreement with the simulation results. The certain deviation between the experimental measurements and the simulation was mainly ascribed to the manufacturing deviation.…”

“…Particle Swarm Optimization (PSO), an intelligent optimization algorithm that imitates animal foraging and shows remarkable advantages for multi-parameter design in many fields, , was used to optimize the in-line 2D architectures. The superiority of the PSO in-line 2D nano antenna structure was evidenced by the experiments, which demonstrated maximum 73.6% improvement of IR camouflage compared with the previous literatures. , Additionally, the in-line 2D configuration was expected for high-efficient direct-writing manufacturing, such as femtosecond laser to increase the productivity and tackle the industrial applications. This study coordinated high-performance design and manufacturing purposes, which was essential for developing future functional structures, including but certainly not limited to IR camouflage for hypersonic aircraft engine and funnels of naval ships.…”

“…Scale bars: 500 nm. (c) Measured IR absorbance/emittance of the manufactured PSO nano antenna for validation, and selective emitter 1 (SE1), selective emitter 2 (SE2), and selective emitter 3 (SE3) in (c) refer to the control samples from previous literatures. In-line 2D represents the unique configuration where antennas with consistent width are lined up in a column, while those with the same length are lined up in a row.…”

“…Other radiation-cooled IR camouflage structures, such as impedance matching multilayer structures, photonic crystal, − anodized alumina, etc., were mainly characterized by their easy-to-manufacture structures, especially for large area manufacturing. However, while achieving radiation heat dissipation, the infrared emittance of the structures was still high within the atmospheric window, indicating that there’s much room for improvements.…”

Luminescence‐Based Infrared Thermal Sensors: Comprehensive Insights

“…[ 330 ] Thermal imaging sensors, which can function in long range surveillance and in complete darkness without any light, are a great tool for spotting possible attackers, it provide a detailed vision relies on tiny temperature change or heat signals, even in smoke and fog. Thermal disparity is quite challenging to conceal, on thermal map, we can obviously observe and spot individuals attempting to camouflage [ 331 ] in along with their environment by hiding behind bushes, in the shadows, or in other ways. The development history of thermal imaging system models reveals considerable improvements made to the practical field over a 40 year period, which made them a valuable tool for defensive system assessments.…”