A Molecular‐Scale Understanding of Misorientation Toughening in Corals and Seashells

Year: 2023

Type: article

Abstract: Biominerals are organic–mineral composites formed by living organisms. They are the hardest and toughest tissues in those organisms, are often polycrystalline, and their mesostructure (which includes nano‐ and microscale crystallite size, shape, arrangement, and orientation) can vary dramatically. Marine biominerals may be aragonite, vaterite, or calcite, all calcium carbonate (CaCO3) polymorphs, differing in crystal structure. Unexpectedly, diverse CaCO3 biominerals such as coral skeletons and nacre share a similar characteristic: Adjacent crystals are slightly misoriented. This observation is documented quantitatively at the micro‐ and nanoscales, using polarization‐dependent imaging contrast mapping (PIC mapping), and the slight misorientations are consistently between 1° and 40°. Nanoindentation shows that both polycrystalline biominerals and abiotic synthetic spherulites are tougher than single‐crystalline geologic aragonite. Molecular dynamics (MD) simulations of bicrystals at the molecular scale reveal that aragonite, vaterite, and calcite exhibit toughness maxima when the bicrystals are misoriented by 10°, 20°, and 30°, respectively, demonstrating that slight misorientation alone can increase fracture toughness. Slight‐misorientation‐toughening can be harnessed for synthesis of bioinspired materials that only require one material, are not limited to specific top‐down architecture, and are easily achieved by self‐assembly of organic molecules (e.g., aspirin, chocolate), polymers, metals, and ceramics well beyond biominerals.

Source: Advanced Materials

DOI: 10.1002/adma.202300373

Authors: Andrew J. Lew, Cayla A. Stifler, Alexandra Tits, Connor A. Schmidt, Andreas Scholl, Astrid Cantamessa, Laura Müller, Yann Delaunois, Philippe Compère, Davide Ruffoni, Markus J. Buehler, Pupa U. P. A. Gilbert

Institutions: Massachusetts Institute of Technology, University of Wisconsin–Madison, University of Liège, Lawrence Berkeley National Laboratory, Advanced Light Source

Language: English

Topic: Calcium Carbonate Crystallization and Inhibition

Subfield: Biomaterials

Field: Materials Science

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $5,250

Funders: National Science Foundation, U.S. Department of Energy, Fonds De La Recherche Scientifique - FNRS, Office of Science, Multidisciplinary University Research Initiative, Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture, Office of Naval Research, Division of Materials Research, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Air Force Office of Scientific Research, Army Research Office

OpenAlex ID: W4322761115