The Squid's Beak May Revolutionize Engineering

Ace905 writes "For years the razor-sharp beak that squid use to eat their prey has posed a puzzle to scientists. Squid are soft and fragile, but have a beak as dense as rock and sharp enough to break through hard shells. Scientists have long wondered why the beak doesn't injure the squid itself as is uses it. New research has just been published in the the journal Science that explains the phenomenon. One of the researchers 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.' Careful examination shows that the beak is formed in a gradient of density, becoming harder towards the tip end. Understanding how to make such hardness gradients could revolutionize engineering anywhere that 'interfaces between soft and hard materials [are required].' One of the first applications researchers envision is prosthetic limbs."

Beaks are neat

[RockModeNick]

Puffer fish also have a shell-crushing beak attached to a relatively soft base, but they have the advantage of a jaw bone(thought they lack skeletal structures like ribs) to propel it. It still always amazed me how they managed to have such soft lips and skin and yet chew apart snails and other hard shelled foods so fast.

Basically it mentions a hardness gradient

[Anonymous Coward]

Basically the article says something about a hardness gradient across the material is why the beak doesn't damage the squid itself. Then they say something about how this idea can be applied to manmade materials. Even that idea isn't entirely new anyways among manmade materials. The traditional samurai sword is forged in such a way that the edge is tempered and hardened to hold razor sharpness, yet the bulk of the blade is not hardened so that it doesn't shatter upon impact.

Re:Basically it mentions a hardness gradient

[dbIII]

The sword example is really just about a mixture. You have areas of soft stuff and areas of hard stuff to get properties between the two extremes for the whole. The tricky details are you have exclusively hard stuff on the cutting edge and exclusively soft stuff on the back edge - but the majority of it is just a lot of different layers of stuff that would be too hard or too soft to be useful on their own. A modern parallel is fibreglass - hard glass mixed in with soft plastic gives you something resonably strong that doesn't shatter like glass.

Re:Beaks are neat

[RockModeNick]

Check out the picture if you've got a strong stomach. http://floridakeystreasures.com/diving/puffer.shtml [floridakeystreasures.com] I can't think of a worse creature to make that particular request of... the blowjob hamster, while also terrible(and I hate hamsters, things bite me all the time at work) at least couldn't bite the thing clean off through a Kevlar condom. My green spotted puffer Shakespeare has nibbled my fingers on accident, too, he's only about an inch in length from being able to take bites of me.

Re:Basically it mentions a hardness gradient

[florescent_beige]

I'm not really familiar with swords but I know a little bit about steel. The Wikipedia description didn't make that much sense to me possibly because it's so brief.

Martensite and pearlite aren't two mutually exclusive phases as such. Pearlite is a combination of ferrite and cementite. Ferrite is alpha-iron, a particular crystal form of pure iron, and cementite is iron carbide Fe3C. So pearlite itself is actually two phases interspersed. In plain carbon steel, pearlite forms from eutectic (.77% carbon) austenite when it is slowly cooled through the eutectoid at 727C.

Less than .77%C and you get pearlite plus a phase of extra ferrite, more than .77%C and you get pearlite and a phase of extra cementite.

This is all for steel that is slowly cooled from austenite. If quenched quickly enough, pearlite formation is suppressed (note that pearlite, being two phases, requires diffusion for the C atoms to migrate out of the ferrite phase into the cementite phase). What you get instead is martensite, which is a metastable phase where the carbon atoms remain interspersed through the iron. It is metastable because the carbons don't really want to be where they are and if they can be made to diffuse (by raising the temperature, a process called annealing) the carbons will move and pearlite will form.

If the quench is not "fast", martensite does not form fully or at all. The result might be less martensite and some pearlite or another form called bainite.

With all that, you can see why I wonder about the statement that martensite and pearlite are "binary phases". Depending on the quench rate, you can get different ratios of finely interspersed zones of the two material forms. Evidently we would like to get martensite on the cutting edge for hardness and pearlite in the middle of the blade for toughness. That means slower cooling in the middle, which I would assume means coating the center of the blade with clay to insulate it and slow the cooling rate.

What the effect of putting "clay and iron" on the blade is a bit mysterious, for the iron to have any value I would think it would have to be allowed to diffuse into the blade during the heat treat process. Also it seems that different carbon contents are used in different parts of the blade which does make sense, higher carbon content causes martensite to form more easily.

What about Head Crabs?

[jameskojiro]

Does their beak work on the same principle? Does a ce-beaked squid grow it back like a missing fingernail?