Lee Ken C, Yu Qi, Erb Uwe
Department of Materials Science and Engineering, University of Toronto, 184 College St. Toronto, Ontario, M5S3E4, Canada.
Sci Rep. 2016 Jun 22;6:28342. doi: 10.1038/srep28342.
Corneal nano-nipple structures consisting of hexagonally arranged protrusions with diameters around 200 nm have long been known for their antireflection capability and have served as biological blueprint for solar cell, optical lens and other surface designs. However, little is known about the global arrangement of these nipples on the ommatidial surface and their growth during the eye development. This study provides new insights based on the analysis of nano-nipple arrangements on the mesoscale across entire ommatidia, which has never been done before. The most important feature in the nipple structures are topological 5- and 7-fold coordination defects, which align to form dislocations and interconnected networks of grain boundaries that divide the ommatidia into crystalline domains in different orientations. Furthermore, the domain size distribution might be log-normal, and the domains demonstrate no preference in crystal orientation. Both observations suggest that the nipple growth process may be similar to the nucleation and growth mechanisms during the formation of other crystal structures. Our results are also consistent with the most recently proposed Turing-type reaction-diffusion process. In fact, we were able to produce the key structural characteristics of the nipple arrangements using Turing analysis from the nucleation to the final structure development.
由直径约200纳米的六边形排列突起组成的角膜纳米乳头结构，长期以来因其抗反射能力而闻名，并一直作为太阳能电池、光学透镜和其他表面设计的生物蓝图。然而，对于这些乳头在小眼表面的整体排列及其在眼睛发育过程中的生长情况，人们知之甚少。本研究基于对整个小眼中尺度上纳米乳头排列的分析提供了新的见解，这在以前从未做过。乳头结构中最重要的特征是拓扑5重和7重配位缺陷，它们排列形成位错和相互连接的晶界网络，将小眼分成不同取向的晶体域。此外，域尺寸分布可能呈对数正态分布，并且这些域在晶体取向上没有偏好。这两个观察结果表明，乳头生长过程可能类似于其他晶体结构形成过程中的成核和生长机制。我们的结果也与最近提出的图灵型反应扩散过程一致。事实上，我们能够使用从成核到最终结构发育的图灵分析来产生乳头排列的关键结构特征。
