Squid beaks and materials science

Clive Thompson's got a fascinating rumination on what a revelation about the composition of the Humboldt squid's razor-sharp beak means for materials science:
There are many weird things about the giant Humboldt squid, but here’s one of the strangest: Its beak. The squid’s beak is one of the hardest organic substances in existence – such that the sharp point can slice through a fish or whale like a Ginsu knife. Yet the beak is attached to squid flesh that itself is the texture of jello. How precisely does a gelatinous animal safely wield such a razor-sharp weapon? Why doesn’t it just sort of, y’know, rip off? It’s as if you tried to carve a roast with a knife that doesn’t have a handle: It would cut into your fingers as much as the roast.

This question has haunted many a marine biologist. So recently a team of materials scientists at the University of California decided to carefully examine the physical properties of the beak. Their discovery? The beak contains a huge gradation of stiffness: The tip of the beak is 100 times more rigid than the base of the beak – so the base can blend easily with the surrounding flesh. Water is the key to the proper functioning of this gradient: If the beak is dried out, the soft base calcifies until it’s nearly as dense and rigid as the peak. (You can read their paper – “The Transition from Stiff to Compliant Materials in Squid Beaks” in PDF format here.)

Now the scientists are trying to figure out how to artificially replicate this remarkable gradient, because it’s so radically different from the way we humans traditionally develop materials. We know how to create materials that are really stiff or really soft, but not ones that slide gradually from one to the other extreme.

The Humboldt squid beak: Diamond-sharp mystery of the briny deep


  1. Cory wrote: “We know how to create materials that are really stiff or really soft, but not ones that slide gradually from one to the other extreme.”

    That’s not entirely true. The Vikings made swords that were soft iron inside the blade, but hard steel on the edges, with a gradual transition.

    Their method was quite simple: Place a rod of soft iron between two rods of steel. Heat the ensemble and twist it into a spiral. Hammer it flat, heat and twist again. Repeat this process several times, and you end with a blade that had graded hardness.

    – Klaus

  2. Screw the jet-packs and hover-cars! I didn’t want those anyway…

    Clearly not only do I have built-in optical binoculars in my future, I also have Wolverine-style claws.

  3. #1, Erm, pattern-welded steel doesn’t actually do what you are describing. If you take two ingredients and fold them together over and over again, you wind up with a consistent mix of both inredients across the whole.

    If you do exactly what you describe, you wind up with a conistent cross section.

    If you want to test this theory, grab two diff colors of playdough and try it yourself.

    If you want a softer spine and harder edge then you need to weld iron (softer) to steel (harder) without mixing the two so that you have a much higher percentage of steel in the places you want hardness (and thus sharpness) and a much higher percentage of iron in the places you want flexibility (softness).

    Pattern welded steel has some great properties, to be sure, but more so than the pattern welding it’s the TEMPERING process that makes metal hard, and thus it’s the tempering process that needs to be modified to make some parts harder then others.

    The Japanese did this by packing clay around the back of the blade during heating, which changed the amount of heat which got into different parts of the metal.

    I don’t know how the vikings did it, but they were very good, wouldn’t be surprised to find they had similar methods.

    However, I think this has little to do with the squids beak, which is cool.

  4. A Japanese sword is made from two pieces of metal. A higher carbon steel is forged around an inner core of lower carbon steel. Tempering is not what makes metal hard. Rapidly cooling metals from a relatively high temperature is called quenching and this is what produces hardness. Tempering is a second step where the metal is reheated to a lower temperature to reduce brittleness. When tempering, the steel can be quenched or allowed to cool slowly. The clay does not affect how heat is applied, but changes the rate of cooling when the blade is quenched. IIRC, Case knives were originally marked with one X after quenching and a second X after tempering.

  5. #4,

    The way I was taught was to heat the blade to red heat, then quench. This results in a very brittle blade. Then, by applying heat with a torch along the spine of the blade, you gradually soften the metal. This is evident in the colors that move across the polished steel surface. When done properly, the edge of the blade will be a straw color, and the spine of the blade will be a violet blue, and the steel will go from extremely hard (and brittle) along the edge to soft and relatively flexible along the spine and a very durable blade overall that needs minimal sharpening.

  6. All this sword nonsense is irrelevant. The difference in stiffness of various forms of steel is minuscule compared to the difference in the squid’s beak- its ONE HUNDRED TIMES as stiff at the tip! A similar difference to that between steel and plastic (according to the table of Young’s moduluses in front of me).

  7. Travelina, I loved the link, thanks. One minor correction before our resident cephlapod rises.

    Scuba SM, that is essentially good advice. To fine tune your results you will also want to time the soak at temperature before quenching. The soak time is critical, this allows the material to fully change to a martensitic structure. Whether air quenching or using water or oil, maintaining the temperature of the quenching medium is important for consistent results. Try using quenching oil as the quenching medium. Preheated oil cools more slowly, producing fewer microscopic cracks and less internal stress. The colors you have noted are oxides and are temperature dependent. The old boys used color to consistently determine temperature. Color Chart It is also important to closely control the temperature and soak time when tempering. I kept kitchen timers near the furnace. I often used a nitrogen purge to control oxidation in the furnace. If you do this a lot, buy a good hardness tester if you haven’t already. After hundreds of tests, I can safely say, you’ll be amazed how small changes in time and temperature of any part of this process affects the hardness and brittleness of the final product.

    Another interesting bit of info, you can tell the type of steel by observing the sparks thrown of by a grinding wheel.

    However, as much as I enjoy working with steel, we don’t even come close to producing any material with these numbers, as Beanolini reminds us.

  8. Any SubGenius will tell you that, as far as the Humboldt’s land-dwelling cousin the prairie squid goes, you’ve got to rip those things off before attempting copulation. I’m not sure how the two species’ beaks compare for sharpness and rigidity, but it is certainly good practice to rip the beaks off of anything you see, ever. Pliers are usually a good tool for this.

  9. PeterNBiddle @2, the catch is that you need the regenerative powers along with them.

    Avraamov @11, creme brulee is relatively trivial. Our highest achievements along these lines in dessert technology:

    1. The slipped custard pie, where you bake a crisp crust and then slip the preformed colloidal custard filling into it

    2. The Pavlova (1, 2), which combines a crisp meringue shell with a fluffy non-crisp meringue interior.

    3. Pretzel Jello, which either originated in, or has been adopted by, la cuisine de Nouvelle Zion.

    None of them are a patch on the gradient from stiff to rubbery in squid beaks.

  10. OK guys, you all know an awful lot about swords, we’re all totally impressed.

    Back on subject, I don’t think the question is about combining different properties in the same material so much as a material of a single consistency with easily mutable properties.

    In your “sword” analogy, the only way to make the metal soft and pliable is with extreme heat. You can imagine how crafting techniques would change if all it took was some salt water.

  11. This would have huge applications in orthopedic surgery. As I understand it the biggest problem with replacing hips and such isn’t making artificial bones that are sturdy enough (titanium is quite sufficient for most non-mutants) but matching the hardness of the graft site so the metal replacement doesn’t grind away the bone it’s butted up against.

    Also, I want one of those theoretical carving knives with a razor sharp blade that transitions into a comfortable handle. Sounds neat!

  12. I’m reminded of Teflon cookware.

    Teflon is non-stick, so … how does it stick to the pan? My layman’s understanding is that Teflon works like this:

    * Start with a bare metal pan.

    * Spray on a coating of 1% Teflon plus 99% sticky stuff. The sticky stuff sticks to the pan; the one percent of Teflon sticks to the sticky stuff.

    * Spray on a coating of 2% Teflon, 98% sticky stuff.

    * … and so on, until you reach 100% Teflon, 0% sticky stuff.

    We might build up our synthetic cephalopod tooth in a similar manner: build by layers across a spectrum of chemistries. Nice little project for the rapid-prototype hobbyist ….

  13. I look forward someday to research into this field to provide specially engineered fasteners that will allow me to nail Jello to the wall.

  14. Steve at Work: yeah, that’s a cut-n-paste of the article text. Click through to click on their link.

    And never add ‘here’ to a sentence to use as a link, just link the name, we all get that links go places and that we can click on them.

  15. #15 Teresa Nielsen Hayden / Moderator:

    i wince shame-faced in the blinding glare of your dessert/physics magnificence.

  16. The gradual transition from hard to soft seems like a very useful property to incorporate into stuff like body armor, helmets, and gloves for sports that tend to beat you up, like mountain biking or rioting at political conventions.

    “We know how to create materials that are really stiff or really soft, but not ones that slide gradually from one to the other extreme.”

    We may not know how to create them yet, but I have something that does that. It’s nowhere near as hard as a squid’s beak, but sometimes it seems like it is.

  17. #8:

    >The difference in stiffness of various forms of steel is minuscule

    As a matter of fact, it’s almost zero. “Stiffness” is technically “modulus of elasticity”, which is the same regardless of temper. Quenching etc. only changes the yield strength, toughness, etc. of the material…i.e., things that happen at higher stress than you would use to ascertain stiffness.

    It should be straightforward to vulcanize rubber such that there’s a gradient of stiffness. As an extreme example, silicone ranges in stiffness from breast implants to something approaching glass (my folks have some old bowls made of hard silicone resin), and the chemistry of producing a gradient from one to the other is absolutely trivial.

    Also, if you leave Tygon tubing (like for an aquarium) in a particular sort of solvent, plasticizers will leach out of the end, and you’ll have a hard PVC tube that gradually transitions to plasticized PVC. This was frustrating when it happened by accident, but you might find it fun.

    #19: It’s simpler than all that. Perfluorosiloxanes are nifty little molecules that have partly unsatisfied silicone-forming groups with a long tail of Teflon-like polymer. A low-temperature process allows this sort of chemical to bond to the oxide on a metal surface in much the same way enamelware does, but the tail groups form a separate phase. The molecule is a similar idea to soap, but the chemistry is more extreme, and more permanent. Presumably, the reaction is all finished by the time you cook with it…

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