Think of Edward Scissorhands with a body made out of Jello. How would he not cut himself to pieces? Researchers have long asked that question about squid—soft squishy creatures with hard, sharp beaks. As this ScienCentral News video explains, the answers could lead to a useful new class of materials.
When hundreds of Humboldt or “Jumbo” squid washed up on the Southern California shore in 2005, most people saw it as a mystery. But researcher Ali Miserez saw it as an opportunity to collect more specimens of squid beaks, which are soft as Jello on one end, but sharp as a knife on the other.
Miserez wanted to understand why having a sharp blade embedded in its body isn’t a problem for a squid. “Imagine if you had a knife, embedded in Jello, and you try to cut meat, you probably make as much damage to yourself and to the Jello, than to the meat itself,” he says. Yet squid make it work, using their razor sharp beaks to rend and devour fish and crustaceans every day.
Besides solving the mystery of how squid manage this trick, Miserez and his team at the University of California, Santa Barbara, have a very practical reason for studying squid beaks, one that ties in with Miserez’s background in engineering. “When you want to join dissimilar materials with very different mechanical properties, so very soft to very hard, usually it's tricky business in materials science,” Miserez explains.
For instance, one major problem in modern medical technology is how to make replacement implants, like artificial knees or hips, integrate with real bone and tissue. Because these implants are metal, or plastic, they can wear away at the organic material. “They create damage at the interface” says Miserez, “and over the years they, after 20 years maybe, the region in the body where they are wears down, so they have to replace it.” Obviously a new kind of material that seamlessly attaches to the body parts around it, and does no damage, would be a huge leap forward in medical technology. Miserez thinks that the structural secret of squid beaks might hold the answer.
Unlike teeth or bone, squid beaks are not made with minerals. Yet they are just as tough, despite being 100 percent organic. How can this be? What makes them so strong?
As they explained in the journal Science, the researchers analyzed the beaks’ chemical structure. They found that it’s a blend of protein, complex carbohydrates, and water, and the blend varies from tip to base. The key to this variation seems to be the interplay between those three ingredients, especially water. Moving from the tip to the base of the beak, water content grows and the beak becomes more and more pliable.
When the beaks were completely dried out for study in the lab, the beak was almost uniformly hard all over.
As Miserez explains, this gradation gives the squid the ability to sidestep the “jello-knife” problem. “You have a graded structure, so it evolves from soft to the hard and it allows to minimize the loads or the stresses where they meet, where the two materials meet. So it minimizes the damage to the structure.”
Miserez wants to apply his findings to creating new, graded materials. Such materials would mimic the mechanical principles of the squid beak, in that there would be a gradation in stiffness or hardness from one end of the material to the other. As he notes, “With this kind of structure, if you could copy it, that would be a good option.”
He hopes such materials could some day be used new types of prosthetics, medical implants, and even specialized glues or adhesives. But researchers still have a lot to learn about squid, and their beaks, before it can happen.
PUBLICATIONS: Science, March, 2008.
RESEARCH FUNDED BY: NIH, Materials Research Science and Engineering Center Program of NSF, NASA University Research and Technology Institute Award, and the Swiss National Science Foundation.