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Shells are tough: red abalone


Red abalone shell / degraffrob / LicenseCC-by-nc-nd - Attribution Non-commercial No Derivatives

The shell of the red abalone resists breakage due to a brick and mortar structure.

Abalone (Haliotis spp.) build their protective shells in seawater, at low-temperatures, using locally plentiful materials. Their shells are 3000 times stronger than their component parts that are 200% stronger than our toughest high-tech ceramics. These master builders layer elastic organic protein material between rigid inorganic calcium carbonate into a nanoscale "brick and mortar" structure. Any cracks that do form in the shell diffuse in intervening protein layers rather than propagate, a flexibility that makes the shell extremely resilient to breaking. (Courtesy of The Biomimicry Institute)
The shell of the red abalone, Haliotis rufescens, "is an example where nature has used readily available materials (e.g. Ca2+ and CO3-2 ions) in seawater in order to generate a multifunctional composite material. The shell is a ceramic/biopolymer hybrid composite structure with two microarchitecturally different sections. The ceramic component is CaCO3 (in two mineralogical forms constituting the two sections of the shell) and the organic is composed of proteins (and, also, likely to contain lipids and polysaccharides). The outer region of the shell has the prismatic section (P) in which the calcitic (rhombohedral CaCO3: R3m) crystallites are oriented perpendicular to the shell plane. The inner region has the nacreous section (N); here pseudohexagonal platelets (single crystals of microtiles) of aragonite (orthorhombic, Pmmm) are oriented parallel to the shell plane. The calcite crystallites are about a few micrometers in edge, and have an aspect ratio of about 5. The aragonite platelets have a thickness of 0.25– 0.4 micrometers, and an edge length of 5 micrometers (aspect ratio of < or = 0.1!)...While the prismatic layer provides the hardness, the nacreous layer, with alternating layers of aragonite platelets and organic film in between, provides the toughness to the shell. In both regions, the organic constitutes less than 5% by volume of the composites. This results in an "ideal" impact resistant material. (Graham and Sarikaya 2000:145-146)
About the inspiring organism
Med_4312570425_708e389c45_b red abalone
Haliotis rufescens Swainson, 1822
Common name: Red abalone

Learn more at
Some organism data provided by: ITIS: The Integrated Taxonomic Information System
Organism/taxonomy data provided by:
Species 2000 & ITIS Catalogue of Life: 2008 Annual Checklist

Threat Categories LONG_NE IUCN Red List Status: Not Evaluated

Bioinspired products and application ideas

Application Ideas: Building structures, composites, orthopedics, dentistry, bone repair, anti-fouling and anti-scaling agents

Industrial Sector(s) interested in this strategy: Manufacturing

Sarikaya Research Group
Mehmet Sarikaya
Materials Science and Engineering Center, University of Washington
Graham, T.; Sarikaya, M. 2000. Growth dynamics of red abalone shell: a biomimetic model. Materials Science and Engineering C. 11(2): 145-153.
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Mayer, G. 2006. New classes of tough composite materials-Lessons from natural rigid biological systems. Materials Science and Engineering C. 26(8): 1261-1268.
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