Parrotfish Teeth: Stiff Biominerals Whose Microstructure Makes Them Tough and Abrasion-Resistant To Bite Stony Corals
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
- Nanyang Technological Univ. (Singapore)
- Univ. of Wisconsin, Madison, WI (United States)
- Biological and Biomimetic Material Laboratory, School of Materials Science and Engineering, Nanyang Technological University, 637553 Singapore
Parrotfish (Scaridae) feed by biting stony corals. To investigate how their teeth endure the associated contact stresses, we examine the chemical composition, nano- and microscale structure, and the mechanical properties of the steephead parrotfish Chlorurus microrhinos tooth. Its enameloid is a fluorapatite (Ca5(PO4)3F) biomineral with outstanding mechanical characteristics: the mean elastic modulus is 124 GPa, and the mean hardness near the biting surface is 7.3 GPa, making this one of the stiffest and hardest biominerals measured; the mean indentation yield strength is above 6 GPa, and the mean fracture toughness is ~.5 MPa·m1/2 , relatively high for a highly mineralized material. This combination of properties results in high abrasion resistance. Fluorapatite X-ray absorption spectroscopy exhibits linear dichroism at the Ca L-edge, an effect that makes peak intensities vary with crystal orientation, under linearly polarized X-ray illumination. This observation enables polarization-dependent imaging contrast mapping of apatite, a method to quantitatively measure and display nanocrystal orientations in large, pristine arrays of nano- and microcrystalline structures. Parrotfish enameloid consists of 100 nm-wide, microns long crystals co-oriented and assembled into bundles interwoven as the warp and the weave in fabric and therefore termed fibers here. These fibers gradually decrease in average diameter from 5 μm at the back to 2 μm at the tip of the tooth. Intriguingly, this size decrease is spatially correlated with an increase in hardness.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Grant/Contract Number:
- AC02-05CH11231
- OSTI ID:
- 1439227
- Journal Information:
- ACS Nano, Journal Name: ACS Nano Journal Issue: 12 Vol. 11; ISSN 1936-0851
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
The hidden structure of human enamel
|
journal | September 2019 |
Residual Strain and Stress in Biocrystals
|
journal | May 2018 |
Synchronous biological feedbacks in parrotfishes associated with pantropical coral bleaching
|
journal | December 2019 |
Diversity and Structure of Parrotfish Assemblages across the Northern Great Barrier Reef
|
journal | January 2019 |
Evidence of friction reduction in laterally graded materials
|
journal | January 2018 |
| Residual strain and stress in biocrystals | text | January 2019 |
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