Department of Physics, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda 278-8510, Japan.
J R Soc Interface. 2021 Nov;18(184):20210505. doi: 10.1098/rsif.2021.0505. Epub 2021 Nov 10.
The structural colours of certain insects are produced by three-dimensional periodic cuticle networks. The topology of the cuticle network is known to be based on the mathematically well-defined triply periodic minimal surface. In this paper, we report the discovery of an I-WP minimal-surface-based photonic crystal on the scale of a longhorn beetle. In contrast to gyroid or diamond surfaces, which are found in butterfly and weevil scales, respectively, the I-WP surface is an unbalanced minimal surface, wherein two subspaces separated by the surface are different in terms of shape and volume fraction. Furthermore, adjacent photonic crystal domains were observed to share a particular crystal plane as their domain boundary, indicating that they were developed as twin crystals. These structural features pose certain new questions regarding the development of biological photonic crystals. We also performed an optical analysis of the structural colour of the longhorn beetle and successfully explained the wavelength of reflection by the photonic bandgap of the I-WP photonic crystal.
某些昆虫的结构色是由三维周期性表皮网络产生的。已知表皮网络的拓扑结构基于数学上定义明确的三重周期性极小曲面。本文报道了在长角甲虫的尺度上发现了一种基于 I-WP 极小曲面的光子晶体。与分别在蝴蝶和象鼻虫鳞片中发现的回旋面或钻石面不同，I-WP 面是一种不平衡的极小曲面，其中由曲面隔开的两个子空间在形状和体积分数方面有所不同。此外，观察到相邻的光子晶体畴共享特定的晶面作为其畴边界，表明它们是作为孪晶发育的。这些结构特征对生物光子晶体的发育提出了一些新的问题。我们还对长角甲虫的结构色进行了光学分析，并成功地通过 I-WP 光子晶体的光子带隙解释了反射波长。
