• DOI:10.1002/adfm.201001546
• Corpus ID: 96221597

Self‐Sharpening Mechanism of the Sea Urchin Tooth

@article{Killian2011SelfSharpeningMO,
  title={Self‐Sharpening Mechanism of the Sea Urchin Tooth},
  author={Christopher E. Killian and Rebecca A. Metzler and Yutao Gong and Tyler H. Churchill and Ian C. Olson and Vasily Trubetskoy and Matthew B. Christensen and John H. Fournelle and Francesco De Carlo and Sidney R. Cohen and Julia Mahamid and Andreas Scholl and Anthony T. Young and Andrew Doran and Fred H. Wilt and Susan N. Coppersmith and Pupa U.P.A. Gilbert},
  journal={Advanced Functional Materials},
  year={2011},
  volume={21}
}

• C. Killian, R. Metzler, +14 authors P. Gilbert
• Published 22 February 2011
• Materials Science
• Advanced Functional Materials

The sea urchin tooth is a mosaic of calcite crystals shaped precisely into plates and fibers, cemented together by a robust calcitic polycrystalline matrix. The tooth is formed continuously at one end, while it grinds and wears at the opposite end, the sharp tip. Remarkably, these teeth enable the sea urchin to scrape and bore holes into rock, yet the teeth remain sharp rather than dull with use. Here we describe the detailed structure of the tooth of the California purple sea urchin Strongylocentrotus purpuratus, and focus on the self‐sharpening mechanism. Using high‐resolution X‐ray photoelectron emission spectromicroscopy (X‐PEEM), scanning electron microscopy (SEM), EDX analysis, nanoindentation, and X‐ray micro‐tomography, we deduce that the sea urchin tooth self‐sharpens by fracturing at discontinuities in the material. These are organic layers surrounding plates and fibers that behave as the “fault lines” in the tooth structure, as shown by nanoindentation. Shedding of tooth components at these discontinuities exposes the robust central part of the tooth, aptly termed “the stone”, which becomes the grinding tip. The precise design and position of the plates and fibers determines the profile of the tooth tip, so as the tooth wears it maintains a tip that is continually renewed and remains sharp. This strategy may be used for the top‐down or bottom‐up fabrication of lamellar materials, to be used for mechanical functions at the nano‐ and micrometer scale.