Coccospheres confer mechanical protection: New evidence for an old hypothesis
Coccospheres confer mechanical protection: New evidence for an old hypothesis
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DOI：
10.1016/j.actbio.2016.07.036
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发表时间：
2016-09-15
影响因子：
9.7
通讯作者：
Langer, G.
中科院分区：
文献类型：
--
作者：
Jaya, B. N.;Hoffmann, R.;Langer, G.
埃米利亚·赫胥黎进化出了极其复杂的球球结构。球球由嵌在多糖基质中的互锁球粒组成。在这项工作中，我们进行了基于原位扫描电子显微镜的压缩测试，并得出结论，球球具有机械保护功能。球球在非弹性变形、恢复和突变断裂前的稳定裂纹扩展方面表现出优异的损伤容忍度，这是单片陶瓷结构所没有的。球球的一些力学特性是由其结构决定的，特别是多糖基质作为一种生物粘合剂。我们的数据为球石团钙化的机械保护假说提供了强有力的证据，没有排除钙化的其他功能，如文献中讨论的各种生化作用。虽然在过去的十年中，人们对珍珠质等壳结构的生物力学进行了研究，但球球的结构是非常独特和复杂的。它是一种多孔的细胞结构，是为了保护海洋中活的藻类细胞而进化出来的，承受着巨大的静水压力。尽管球粒球是由非常脆的成分如碳酸钙制成的，但我们的研究发现，球粒球具有显著的损伤容忍度，特别是由于其互锁的球粒结构。这将对仿生设计产生影响，特别是与高压应用有关的设计。(C) 2016材料学报Elsevier Ltd.出版。版权所有。
Emiliania huxleyi has evolved an extremely intricate coccosphere architecture. The coccosphere is comprised of interlocking coccoliths embedded in a polysaccharide matrix. In this work, we performed in situ scanning electron microscopy based compression tests and conclude that coccospheres have a mechanical protection function. The coccosphere exhibits exceptional damage tolerance in terms of inelastic deformation, recovery and stable crack growth before catastrophic fracture, a feature, which is not found in monolithic ceramic structures. Some of the mechanical features of the coccospheres are due to their architecture, especially polysaccharide matrix that acts as a kind of bio-adhesive. Our data provide strong evidence for the mechanical protection-hypothesis of coccolithophore calcification, without excluding other functions of calcification such as various biochemical roles discussed in the literature.Statement of SignificanceAlthough bio-mechanics of shell structures like nacre have been studied over the past decade, coccospheres present an architecture that is quite distinct and complex. It is a porous cell structure evolved to protect the living algae cell inside it in the oceans, subjected to significant hydrostatic pressure. Despite being made of extremely brittle constituents like calcium carbonate, our study finds that coccospheres possess significant damage tolerance especially due to their interlocking coccolith architecture. This will have consequences in bio-mimetic design, especially relating to high pressure applications. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.