Gravity enables self-assembly
Gravity enables self-assembly
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DOI：
10.1002/ntls.20220007
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发表时间：
2022-07-01
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影响因子：
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通讯作者：
Deshpande, Vikram S.
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文献类型：
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作者：
Grega, Ivan;Shaikeea, Angkur J. D.;Deshpande, Vikram S.
颗粒组装体的结晶对于快速和可扩展地产生具有从结构材料到微结构电池电极的应用的结构材料具有广泛的意义。虽然在纳米到微米尺度上对胶体自组装的理解已经取得了重大进展，但硬球干组装的组织机制仍然不清楚。在这里，我们调查结晶的单尺寸硬球和没有施加振动。使用X射线计算机断层扫描分析加上离散元模拟，我们解开重力和施加振动的干球的三维自组装的作用。我们使用这些见解介绍重力介导的外延晶体生长与缓慢倾倒球播种模板。与振动诱导结晶相反，这种方法可以形成具有密堆积和相当令人惊讶的非密堆积亚稳颗粒排列的大单晶。我们的研究结果为无缺陷颗粒组装体的可扩展制造提供了见解，这些组装体可用作空间保持模板来制造蜂窝材料，例如反蛋白石和其他相关拓扑结构。硬球的自组装是可规模化制造微结构固体的关键步骤。通过振动实验，3D X射线断层扫描观察和模拟的组合，我们阐明了引力在硬球自组装中的关键作用，设计了种子模板，不仅可以诱导硬球自组装成稳定的紧密结构，堆积晶体结构，但也相当违反直觉地转变为亚稳态单晶结构。
Crystallization of granular assemblies has broad implications for rapid and scalable creation of architected materials with applications ranging from structural materials to microarchitected battery electrodes. While significant advances have been made in understanding colloidal self-assembly at nano to micro scale, the governing mechanisms for organization of dry assemblies of hard spheres remain unclear. Here, we investigate crystallization of mono-size hard spheres with and without imposed vibration. Using X-ray computed tomographic analysis coupled with discrete-element simulations, we unravel the roles of gravity and imposed vibration on the three-dimensional self-assembly of the dry spheres. We use these insights to introduce gravity-mediated epitaxial crystal growth with slow pouring of balls on seeding templates. Contrary to vibration-induced crystallization, this method can form large single crystals with both close-packed and rather surprisingly, nonclose-packed metastable particle arrangements. Our results provide insight for the scalable manufacture of defect-free granular assemblies that can be used as space-holding templates to manufacture cellular materials, such as inverse opals and other related topologies.Key points:Self-assembly of hard spheres is a critical step for the scalable manufacture of micro-architected solids.Via a combination of vibration experiments, 3D X-ray tomographic observations, and simulations, we elucidate the critical role of gravity in the self-assembly of hard spheres.We design seeding templates that can not only induce the self-assembly into stable close-packed crystal structures but also rather counterintuitively into metastable single crystal structures.