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Squid Beaks for a Better Prosthetic Fit? The razor-sharp beaks that giant squids use to
attack whales--and maybe even Captain Nemo's submarine--might one
day lead to improved artificial limbs for people, according to an
article by the Associated Press (AP). That deadly beak may be a
surprise to many people, and has long posed a puzzle for
scientists. They wonder how a creature without any bones can
operate it without hurting itself.
Now, researchers at the University of California, Santa Barbara
(UCSB), report in the journal Science that they have an
explanation. The beak, made of hard chitin and other materials,
changes density gradually from the hard tip to a softer, more
flexible base where it attaches to the muscle around the squid's
mouth, the researchers found. That means the tough beak can chomp
away at fish for dinner, but the hard material doesn't press or rub
directly against the squid's softer tissues.
Herbert Waite, a professor in the university's Department of
Molecular, Cellular & Developmental Biology and co-author of
the paper ("Jumbo Squid Beaks: Inspiration for design of robust
organic composites," A. Miserez, Y. Li, J.H. Waite, and F. Zok,
2007, Acta Biomaterialia 3: 139-149), described the squid
beak as like placing an X-Acto blade in a block of fairly firm
Jell-O and then trying to use it to chop celery. The base of the
blade would damage the gelatin, but because of the change in
density the base of the beak doesn't damage the squid, he pointed
out. The squid solves the problem by changing the beak composition
progressively, rather than abruptly, so that its tip can pierce
prey without harming the squid in the process.
The researchers calculated the changes by carefully measuring
the ratios of chitin--the material in insect shells--water and
proteins in the beaks of Humboldt squid, showing gradual changes
from tip to base. Waite said it was the first time this had been
measured. He said he was surprised that the main difference in
density resulted from the amount of water included in each part of
the beak.
Waite noted that such graduated materials could have broad
applications in biomedical materials. "Lots of useful information
could come out of this for implant materials, for example," Waite
told the AP. "Interfaces between soft and hard materials occur
everywhere."
Frank Zok, professor and associate chair of the UCSB's
Department of Materials, said he had always been skeptical of
whether there is any real advantage to materials that change their
properties gradually from one part to another, "but the squid beak
turned me into a believer.
"If we could reproduce the property gradients that we find in
squid beak, it would open new possibilities for joining materials,"
Zok said in a statement. "For example, if you graded an adhesive to
make its properties match one material on one side and the other
material on the other side, you could potentially form a much more
robust bond."
The researchers are learning lessons that can be applied to
medical materials in the future, said Phillip B. Messersmith of the
Department of Biomedical Engineering at Northwestern University,
Evanston, Illinois. Messersmith, who was not part of the research
team, noted that hard medical implants made of metal or ceramic are
often imbedded in soft tissues. "The lessons here from nature might
be useful in transitions between devices and the tissues they are
imbedded in," he told the AP.
Ali Miserez, a UCSB researcher and co-author of the paper,
suggested the research could point the way to new types of medical
materials. "We could maybe imagine creating a full prosthesis that
mimics the chemistry of the beak, so that it matches the elasticity
of cartilage on one side and, on the other side, you could create a
material which is very stiff and abrasion resistant," he said in an
interview provided by Science.
The research was funded by the National Institutes of Health,
National Science Foundation, NASA and the Swiss National Science
Foundation.
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