Reduction in kelp forests altered sea otter and sea urchin behavior, restructuring mechanisms of ecosystem control.
Image credit: Michael Langhans (photographer).
Edited by David A. Weitz, Harvard University, Cambridge, MA, and approved October 13, 2015 (received for review September 17, 2015)
Significance
Substantial experimental and theoretical work has been devoted to understand the equilibrium properties of curved crystals, but these crystals’ stability under mechanical forces remains largely unexplored and unknown. Understanding how curved crystals can adapt their shape and resist failure is of fundamental importance because these structures are at the forefront in the drive to fabricate new functionalized self-assembled materials. Here, we address these questions by numerical simulations of the deformation of colloidal crystalline shells. Our results highlight the fundamental role played by geometrically necessary crystal defects in controlling mechanical stability and plastic rearrangements of the shell.
Abstract
Designing and controlling particle self-assembly into robust and reliable high-performance smart materials often involves crystalline ordering in curved spaces. Examples include carbon allotropes like graphene, synthetic materials such as colloidosomes, or biological systems like lipid membranes, solid domains on vesicles, or viral capsids. Despite the relevance of these structures, the irreversible deformation and failure of curved crystals is still mostly unexplored. Here, we report simulation results of the mechanical deformation of colloidal crystalline shells that illustrate the subtle role played by geometrically necessary topological defects in controlling plastic yielding and failure. We observe plastic deformation attributable to the migration and reorientation of grain boundary scars, a collective process assisted by the intermittent proliferation of disclination pairs or abrupt structural failure induced by crack nucleating at defects. Our results provide general guiding principles to optimize the structural and mechanical stability of curved colloidal crystals.
Footnotes
- ↵1To whom correspondence should be addressed. Email: carmen.miguel{at}ub.edu.
Author contributions: C.N., A.L.S., S.Z., and M.C.M. designed research; C.N., A.L.S., S.Z., and M.C.M. performed research; C.N. and M.C.M. analyzed data; and S.Z. and M.C.M. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1518258112/-/DCSupplemental.
Freely available online through the PNAS open access option.
Deformation and failure of curved crystal shells
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- Physical Sciences
- Physics
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