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Proc Natl Acad Sci U S A. 2015 Jan 06;112(1):14-9. doi: 10.1073/pnas.1411559112. Epub 2014 Dec 22.

Wrinkling crystallography on spherical surfaces.

Proceedings of the National Academy of Sciences of the United States of America

Miha Brojan, Denis Terwagne, Romain Lagrange, Pedro M Reis

Affiliations

  1. Departments of Mechanical Engineering.
  2. Civil and Environmental Engineering, and.
  3. Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139.
  4. Departments of Mechanical Engineering, Civil and Environmental Engineering, and [email protected].

PMID: 25535355 PMCID: PMC4291636 DOI: 10.1073/pnas.1411559112

Abstract

We present the results of an experimental investigation on the crystallography of the dimpled patterns obtained through wrinkling of a curved elastic system. Our macroscopic samples comprise a thin hemispherical shell bound to an equally curved compliant substrate. Under compression, a crystalline pattern of dimples self-organizes on the surface of the shell. Stresses are relaxed by both out-of-surface buckling and the emergence of defects in the quasi-hexagonal pattern. Three-dimensional scanning is used to digitize the topography. Regarding the dimples as point-like packing units produces spherical Voronoi tessellations with cells that are polydisperse and distorted, away from their regular shapes. We analyze the structure of crystalline defects, as a function of system size. Disclinations are observed and, above a threshold value, dislocations proliferate rapidly with system size. Our samples exhibit striking similarities with other curved crystals of charged particles and colloids. Differences are also found and attributed to the far-from-equilibrium nature of our patterns due to the random and initially frozen material imperfections which act as nucleation points, the presence of a physical boundary which represents an additional source of stress, and the inability of dimples to rearrange during crystallization. Even if we do not have access to the exact form of the interdimple interaction, our experiments suggest a broader generality of previous results of curved crystallography and their robustness on the details of the interaction potential. Furthermore, our findings open the door to future studies on curved crystals far from equilibrium.

Keywords: curved surfaces; defects; mechanical instabilities; packing; pattern formation

References

  1. Phys Rev Lett. 2014 Jun 6;112(22):225502 - PubMed
  2. Phys Rev Lett. 2006 Jun 30;96(25):258001 - PubMed
  3. Proc Natl Acad Sci U S A. 2008 Dec 9;105(49):19132-5 - PubMed
  4. Science. 2003 Mar 14;299(5613):1716-8 - PubMed
  5. Phys Rev A Gen Phys. 1988 Jul 15;38(2):1005-1018 - PubMed
  6. Proc Natl Acad Sci U S A. 2013 Aug 6;110(32):12893-8 - PubMed
  7. Phys Rev Lett. 2011 Jun 10;106(23):234301 - PubMed
  8. Nature. 2010 Dec 16;468(7326):947-51 - PubMed
  9. Adv Mater. 2014 Oct;26(38):6608-11 - PubMed
  10. Proc Natl Acad Sci U S A. 2006 Aug 15;103(33):12323-8 - PubMed
  11. Nat Mater. 2012 Nov;11(11):948-51 - PubMed
  12. Phys Rev Lett. 2005 Feb 4;94(4):040601 - PubMed
  13. Science. 2002 Nov 1;298(5595):1006-9 - PubMed

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