弹指神功# Animals - 动物园
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http://news.sciencemag.org/sciencenow/2012/06/mantis-shrimp-sma
Mantis Shrimp Smash!
by Gisela Telis on 7 June 2012, 2:24 PM
The peacock mantis shrimp packs a powerful punch. The crustacean uses its
hammerlike claws to smash through mollusk shells and even aquarium glass
without getting injured. Now, a new study reveals what makes its claws so
tough: a unique composition and structure that stops cracks in their tracks
—one that could help engineers design lighter, stronger materials for
military, medical, and other applications.
"This is an absolutely gorgeous study, a tour de force … that opens so many
new windows for biologists and engineers," says Sheila Patek, a biologist
at the University of Massachusetts, Amherst, who first measured the speed of
the mantis shrimp's blows. "Plus, I really wanted to know all this stuff,
and I'm glad someone did it."
Though mantis shrimp are relatively common, a lot about them isn't. The
colorful crustaceans have remarkable vision, unusually resilient armor, and
the fastest punch on earth. When they strike, they swing out their dactyl
clubs, armlike appendages normally held close to their bodies, at 80
kilometers per hour, accelerating faster than a .22-caliber bullet. Mantis
shrimp use this mechanism to smash their often hard-shelled prey, and can do
so as many as 50,000 times between molts without destroying their clubs.
David Kisailus, a chemical engineer at the University of California,
Riverside, and his team wondered how mantis shrimp could keep up their
hitting without catastrophic damage to their clubs. So they dissected the
clubs of 15 mantis shrimp (who just grow them back if they're removed).
Using everything from scanning electron microscopes to x-rays, the team
examined the club's inner structure and found a complex arrangement of
layers.
The impact region features a highly crystallized form of the mineral
hydroxyapatite, a key ingredient in human bones and teeth. Below that are
more layers of hydroxyapatite, this time in an amorphous, noncrystallized
form. The innermost region contains chitin, a less stiff material often
found in the exoskeletons of crustaceans stacked in helices with
hydroxyapatite filling in between the stacks. The differences in hardness,
stiffness and orientation between the three layers allow small cracks to
form but prevent them from growing or spreading, so the club stays intact,
the researchers report online today in Science.
"It's counterintuitive: Mother Nature prevents catastrophic failures by
allowing local failures," says Kisailus. "It's that architecture that makes
them so strong."
The team aims to use that architecture to build lighter and more effective
armor for soldiers, fortify cars and other vehicles, and even protect
athletes from concussions. Kisailus and colleagues are already developing
materials that mimic the structure of the mantis shrimp's club, and
preliminary tests show the materials are bulletproof, he says.
Mantis Shrimp Smash!
by Gisela Telis on 7 June 2012, 2:24 PM
The peacock mantis shrimp packs a powerful punch. The crustacean uses its
hammerlike claws to smash through mollusk shells and even aquarium glass
without getting injured. Now, a new study reveals what makes its claws so
tough: a unique composition and structure that stops cracks in their tracks
—one that could help engineers design lighter, stronger materials for
military, medical, and other applications.
"This is an absolutely gorgeous study, a tour de force … that opens so many
new windows for biologists and engineers," says Sheila Patek, a biologist
at the University of Massachusetts, Amherst, who first measured the speed of
the mantis shrimp's blows. "Plus, I really wanted to know all this stuff,
and I'm glad someone did it."
Though mantis shrimp are relatively common, a lot about them isn't. The
colorful crustaceans have remarkable vision, unusually resilient armor, and
the fastest punch on earth. When they strike, they swing out their dactyl
clubs, armlike appendages normally held close to their bodies, at 80
kilometers per hour, accelerating faster than a .22-caliber bullet. Mantis
shrimp use this mechanism to smash their often hard-shelled prey, and can do
so as many as 50,000 times between molts without destroying their clubs.
David Kisailus, a chemical engineer at the University of California,
Riverside, and his team wondered how mantis shrimp could keep up their
hitting without catastrophic damage to their clubs. So they dissected the
clubs of 15 mantis shrimp (who just grow them back if they're removed).
Using everything from scanning electron microscopes to x-rays, the team
examined the club's inner structure and found a complex arrangement of
layers.
The impact region features a highly crystallized form of the mineral
hydroxyapatite, a key ingredient in human bones and teeth. Below that are
more layers of hydroxyapatite, this time in an amorphous, noncrystallized
form. The innermost region contains chitin, a less stiff material often
found in the exoskeletons of crustaceans stacked in helices with
hydroxyapatite filling in between the stacks. The differences in hardness,
stiffness and orientation between the three layers allow small cracks to
form but prevent them from growing or spreading, so the club stays intact,
the researchers report online today in Science.
"It's counterintuitive: Mother Nature prevents catastrophic failures by
allowing local failures," says Kisailus. "It's that architecture that makes
them so strong."
The team aims to use that architecture to build lighter and more effective
armor for soldiers, fortify cars and other vehicles, and even protect
athletes from concussions. Kisailus and colleagues are already developing
materials that mimic the structure of the mantis shrimp's club, and
preliminary tests show the materials are bulletproof, he says.
