The mesoscale order of nacreous pearls

Jiseok Gim; Alden Koch; Laura M Otter; Benjamin H Savitzky; Sveinung Erland; Lara A Estroff; Dorrit E Jacob; Robert Hovden

doi:10.1073/pnas.2107477118

The mesoscale order of nacreous pearls

Proc Natl Acad Sci U S A. 2021 Oct 19;118(42):e2107477118. doi: 10.1073/pnas.2107477118.

Authors

Jiseok Gim¹, Alden Koch², Laura M Otter³, Benjamin H Savitzky⁴, Sveinung Erland⁵, Lara A Estroff^{6

7}, Dorrit E Jacob³, Robert Hovden^{8

9}

Affiliations

¹ Department of Materials Science & Engineering, University of Michigan, Ann Arbor, MI 48109.
² Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109.
³ Research School of Earth Sciences, Australian National University, Canberra, ACT 2600, Australia.
⁴ National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
⁵ Department of Maritime Studies, Western Norway University of Applied Sciences, 5528 Haugesund, Norway.
⁶ Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853.
⁷ Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853.
⁸ Department of Materials Science & Engineering, University of Michigan, Ann Arbor, MI 48109; hovden@umich.edu.
⁹ Applied Physics Program, University of Michigan, Ann Arbor, MI 48109.

Abstract

A pearl's distinguished beauty and toughness are attributable to the periodic stacking of aragonite tablets known as nacre. Nacre has naturally occurring mesoscale periodicity that remarkably arises in the absence of discrete translational symmetry. Gleaning the inspiring biomineral design of a pearl requires quantifying its structural coherence and understanding the stochastic processes that influence formation. By characterizing the entire structure of pearls (∼3 mm) in a cross-section at high resolution, we show that nacre has medium-range mesoscale periodicity. Self-correcting growth mechanisms actively remedy disorder and topological defects of the tablets and act as a countervailing process to long-range disorder. Nacre has a correlation length of roughly 16 tablets (∼5.5 µm) despite persistent fluctuations and topological defects. For longer distances (>25 tablets , ∼8.5 µm), the frequency spectrum of nacre tablets follows [Formula: see text] behavior, suggesting that growth is coupled to external stochastic processes-a universality found across disparate natural phenomena, which now includes pearls.

Keywords: SEM; TEM; mesoscale; nacre; pearls.

Publication types

Research Support, Non-U.S. Gov't