Broadband and Ultrathin Infrared Stealth Sheets

Abstract

To effectively hide objects and render them invisible to thermographic detectors, their thermal signatures in the infrared (IR) region of the spectrum may be concealed. However, to conceal broadband spontaneous thermal emission of objects, covering the mid-and long-IR is a major obstacle. Here, metallic-dielectric nanostructures and microscale IR emitters are integrated and transferred onto thin flexible substrates to realize IR stealth sheets. The nanostructures absorb and scatter a broad band of IR wavelengths to reduce both reflection and transmission to below 5% across a wide range from 2.5 to 15.5 μm, and thus significantly attenuate the amount of IR signals propagating toward the detectors. Results show that the nanostructures with their unique properties can almost completely conceal the thermal emission from objects and blend them into their surroundings. In addition, micro-emitters thermally isolated from the broadband absorbers can present false thermography to deceive IR detectors and heat-sensing cameras.

Carbon Vesicles: A Symmetry‐Breaking Strategy for Wide‐Band and Solvent‐Processable Ultrablack Coating Materials

“…Ultrablack materials, which are featured by their excellent light‐absorption properties, play important roles in applications, such as high‐resolution optical sensing, [ 1–4 ] solar energy harvesting, [ 5–8 ] infrared light source, [ 9,10 ] and infrared stealth. [ 11,12 ] Various ultrablack structures constructed of carbon, [ 13–17 ] metal, [ 18,19 ] and semiconductor [ 20–23 ] have been reported. Among these structures vertically aligned carbon nanotube arrays (VA‐CNT arrays) exhibit the lowest hemispherical reflectance of 0.045%.…”

Beyond the Visible: Bioinspired Infrared Adaptive Materials

“…Moghimi et al developed remarkable IR stealth sheets based on metallic silver nanoparticles with high extinction coefficients and silicon dielectric nanowires with high indexes of refraction, combined with an array of addressable microemitters and a network of air-channels, as shown in Figure 5b. [48] The stealth sheets, with such unique architectures, absorbed and scattered incident light, thereby obstructing the propagation of IR radiation. Importantly, the heat dissipated through the nanostructures and cooling air-channels instead of accumulating inside the hidden areas.…”

High-temperature infrared camouflage with efficient thermal management

“…To control the surface emittance, nanostructure-based surfaces (e.g., metasurfaces 3,8 and metallic-dielectric nanowires 9 ) or films (metal 10 , semiconductor 11,12 , and multilayer films [13][14][15][16][17] ) are demonstrated with low-surface emittance over the whole IR range, and yet the radiative heat transfer is blocked, causing severe heat instability 18 . Wavelength-selective emitters [19][20][21][22][23][24][25] with radiative cooling [26][27][28][29][30][31] in the non-atmospheric window (5-8 μm) 18,20,32 are adopted to mitigate the heat instability without influencing the IR camouflage.…”