Abalone Shell—Designed for Strength

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Nature creates many materials far stronger than any human-made materials, diamonds for example. Scientists who study biomimicry have found another paragon of strength in nature: the marine invertebrate abalone. Abalone produces a shell five times more resistant to breakage than synthetic ceramics, but the shell’s composition is 3,000 times stronger than its main constituent, the mineral aragonite. Scientists have pondered how abalone manages this feat. “Its strength is very likely due to structure,” said the University of Wisconsin physicist Pupa Gilbert to the LiveScience correspondent Corey Binns in 2007. Abalone shell is composed of a small amount of organic matter in a calcium carbonate material called nacre, which the mollusk builds into an irregular tiled plate. The abalone
laminates the nacre plate within protein sheets; protein’s positive charge enables it to bind to the negatively charged nacre. This layered shell protects the abalone against direct impacts but also provides another safety mechanism: The protein layers slide against one another to absorb energy from indirect blows. A cement mixer can roll over an abalone shell without causing even one crack.

In 2005 the mechanical engineer Kenneth Vecchio of the University of California, San Diego, succeeded in making an aluminum-titanium material modeled after abalone shell. Vecchio’s formula has been used by the aerospace industry for providing steel-like strength to space vehicles while weighing much less. This same material may soon be used in military body
armor. The University of Washington materials scientist Mehmet Sarikaya explained to the New York Times some of nature’s mysteries: “Nobody knows all the details. Nature has designed an interface of organic and inorganic materials interpenetrating in ways that we cannot yet equal.” Vecchio pointed out, “When you think about it, an abalone shell is just
chalk.” The abalone shell provides one of many examples in nature in which strength comes from simplicity.