Radiative cooling, which normally requires relatively high infrared (IR) emissivity, is one of the insects’ effective thermoregulatory strategies to maintain their appropriate body temperature. Recently, the physical correlation between the delicate biological microstructures and IR emissivity for thermal radiation draws increased attention. Here, a scent patch region on the hindwing of Rapala dioetas butterfly is found to exhibit enhanced IR emissivity compared with the non-scent patch regions. A series of optical simulations are conducted to differentiate the effect of biological structures and material composition on the high IR emissivity. Besides the intrinsic IR absorption (emission) of chitin (the main composition of butterfly wings), the hierarchical microstructures of the scent patch scale further improve the IR absorption (emission) through the increased inner surface area and multi-scattering effect. This enhancement of IR emissivity enables the butterfly to efficiently radiate heat from the scent patch region to the environment with a limited volume of chitin. This study of the correlation between IR emissivity and microstructural designs may offer additional pathways to engineer bioinspired materials and systems for radiative cooling applications.

中文翻译：

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蝴蝶翼状鳞片的分级微观结构增强红外发射率

辐射冷却通常需要相对较高的红外（IR）发射率，是昆虫维持其适当体温的有效温度调节策略之一。近来，精致的生物微观结构与热辐射的IR发射率之间的物理相关性引起了越来越多的关注。在这里，在Rapala dioetas的后翅上有一个气味斑块区域发现蝴蝶与非气味斑块区域相比具有增强的红外发射率。进行了一系列光学模拟，以区分生物结构和材料成分对高红外发射率的影响。除了甲壳质（蝴蝶翅膀的主要成分）固有的红外吸收（发射），气味斑块鳞片的分层微结构通过增加的内表面积和多重散射效应进一步改善了红外吸收（发射）。IR发射率的这种增强使蝴蝶能够用有限体积的几丁质将蝴蝶结区域中的热量有效地辐射到环境中。