Abstract
Abstract Thermal camouflage, which is used to conceal objects in the infrared vision for confrontation with infrared detection in civilian or military applications, has garnered increasing attraction and interest recently. Compared with conductive thermal camouflage, that is to tune heat conduction to achieve equivalent temperature fields, radiative thermal camouflage, based on emissivity engineering, is more promising and shows much superiority in the pursuit of dynamic camouflage technology when resorting to stimuli-responsive materials. In this paper, we demonstrate the emissivity-engineered radiative metasurface to realize dynamic thermal camouflage functionality via a flying laser heat source on the metal-liquid-crystal-metal (MLCM) platform. We employ a rigorous coupled-wave algorithm to calculate the surface emissivity of Au/LC/Au microstructures, where the LC-orientation angle distribution is quantified by minimizing the emitted thermal energy standard deviation throughout the whole plate. Emissivity engineering on the MCLM platform is attributed to multiple magnetic polariton resonance, and agrees well with the equivalent electric circuit analysis. Through this electrical modulation strategy, the moving hot spot in the original temperature field is erased and a uniform temperature field is observed in the infrared camera instead, demonstrating the very good dynamic thermal camouflage functionality. The present MLCM-based radiative metasurface may open avenues for high-resolution emissivity engineering to realize novel thermal functionality and develop new applications for thermal metamaterials and meta-devices.
Highlights
The dynamic structural colors in the skin of chameleons and cephalopods enable them to blend into the background environment adaptively, they are known as the camouflage masters in the natural world [1,2,3]
We propose a general strategy to dynamically tune the thermal emission from a metal-liquidcrystal-metal (MLCM) radiative metasurface for dynamic thermal camouflage
We demonstrate the feasibility of a radiative MLCM metasurface consisting of Au/liquid crystals (LCs)/Au gratings to realize thermal camouflage by structuring the surface emissivity
Summary
The dynamic structural colors in the skin of chameleons and cephalopods enable them to blend into the background environment adaptively, they are known as the camouflage masters in the natural world [1,2,3]. The sophisticated architecture of the dynamic color-changing system has inspired the engineering of various adaptive artificial materials and devices, like optoelectronic displays, soft robots, and camouflage systems, and their working spectra have been extended beyond the visible light with many civilian and military applications [1,2,3,4,5]. Thermal camouflage, with the aim of concealing objects from infrared (IR) imaging, has attracted increasing attention, and can be used to incapacitate IR detection [6,7,8,9,10,11,12]. One way is to change the target temperature as close as possible to approximate the background temperature when their surface emissivities are comparable, and the other way is to change the target surface emissivity to generate the same amount of emitted thermal energy as the
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