[Image above] Jiseok Gim, materials science and engineering Ph.D. candidate, loads a sample into the JEOL 3100R05 electron microscope in the Michigan Center for Materials. Gim and a group of scientists used electron microscopy to investigate the nanomechanics of nacre’s strength. Credit:Evan Dougherty, Michigan Engineering
NACRE是一种代表超过其部件总和的材料。
又称母亲珍珠，科学家们已经长期研究了这款彩虹物软体动物壳衬里来解锁其秘密，因为纳米是一种令人难以置信的强壮的生物材料。
For instance, scientists recently developed基于细菌的制造地球和超越合成珍珠的方法，以及纳克人的结构甚至灵感的技术3D印刷体护甲.
纳卡尔的结构和组合物都是已知的，纳加由碳酸钙或金属石的多边形血小板组成，它们与有机材料一起堆叠和砂浆。然而，作为一种材料，珍珠果比这些单独部件的性质所预测的更难度。
那么纳卡尔力量的秘诀是什么？
一个新的open-access paperdelves into the nanomechanics of nacre to unveil how its structure provides the biomaterial with such exceptional abilities.
“我们人类可以使用不自然环境制造更坚固的材料，例如极端热量和压力。但我们无法复制软体动物所取得的纳米工程，“罗伯特霍夫登，密歇根大学材料科学与工程的高级作者和助理教授university press release. “Combining the two approaches could lead to a spectacular new generation of materials, and this paper is a step in that direction.”
Hovden and a team of scientists from the University of Michigan (Ann Arbor, Mich.), Macquarie University (Sydney, Australia), Université de Bourgogne Franche-Comté (Dijon, France), and University Erlangen-Nürnberg (Erlangen, Germany) set out to track what happens to nacre’s nanostructure when stress is applied. Using high-resolution scanning/transmission electron microscopy (S/TEM), they watched in real-time how samples of nacre respond to nanoindentation.
结果表明，虽然珍珠菌的有机成分仅代表了少量的材料（2-5重量％），但它对其性能产生了不成比例的影响。
When the scientists compressed the nacre samples with a nanoidentor tip, they saw that individual aragonite bricks within nacre’s structure compressed together, squishing the organic mortar out of the way. With the organic material pushed to the side, individual bricks came into contact with one another, structurally locking with neighboring bricks.
The bricks joined together to form bulk aragonite, which can better distribute strain within the material compared to those individual bricks. This joining allows nacre to have better resilience under pressure, as the organic material absorbs the applied energy and helps prevent the hard biomaterial from cracking (or at least limiting crack propagation).
通过使其结构移位，珍珠虫可以吸收比单片金属岩更高的机械能量约为1-3倍。“所以局部变形和大规模变形之间的过渡是使珍珠变得如此艰难，”Hovden在下面的视频中说。
难以置信的是,整个过程是reversible-whenstrain is removed, the organic material squishes back into its mortar position between the bricks, setting the process up to repeat again. This reversibility provides nacre with exceptional resilience to repeated deformation, allowing the material to exhibit its impressive strength, hardness, and ductility.
The team’s S/TEM results open up the possibility of using similar experimental approaches to investigate a broad range of other materials. And, with a better understanding of how nacre’s structure makes the biomaterial so tough, the scientists think their results might inspire approaches to nanoengineer composite surfaces that are synthetically tough as well.
开放式纸张，发表于Nature Communications， 是 ”纳米级变形力学揭示了纳卡尔的韧性Pinna nobilis.shell“（DOI：10.1038 / S41467-019-12743-Z）。