Hi I’m Dr. Sabrina Stierwalt, and I’m Everyday Einstein bringing you Quick and Dirty Tips to help you make sense of science.
Scientists and engineers find inspiration everywhere and now they are looking to mollusks for ways to build stronger airplanes as well as lighter, stronger race cars.
How can spineless, soft-bodied snails hold the key to strengthening our aircraft? A recent study has found that the mouths of limpets, a type of mollusk found in southern Europe, are actually home to the strongest biological material ever tested.
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The Spider and the Fly Can’t Make a Deal
Until recently, spider silk has held the title of the strongest material found in nature. Different spiders spin different kinds of silk and a single spider may make up to 7 different kinds of silk used for different purposes. All, however, are incredibly strong.
A single strand of spider silk is stronger than steel at only 1/10 the thickness of a human hair. The creators of Spiderman dramatically underestimated the strength of his web by depicting it as way thicker than it needed to be to sling his weight all over the city.
Spiders use their webs as lifelines, to flee from danger, and of course to spin webs to catch their prey. Spiders start with liquid proteins and spin them into solid webs through a very complicated and not completely understood process that involves applying a certain amount of pressure to the silk itself. Ongoing research is attempting to unlock the secrets of this process and recreate it in a lab. The resulting human-made material would be so versatile and so strong that it would have the potential to replace the many, many plastics we use in our everyday lives.
Lucky for us, spiders big enough to catch people in their webs only exist in the world of JRR Tolkien.
The Lives of Limpets
However, recently the spider has been dethroned as the keeper of nature’s strongest material. That title has been taken by limpets. Limpets are a type of mollusk, a soft-bodied invertebrate with an outer shell, that spend most of their time clinging onto large rocks along the seashore so as not to be washed away with the tide.
As the tide starts to ebb, the limpets, who have been moving around under the surface of the water looking for food, begin to scatter to find a place to anchor themselves to the rock so as not to be carried out to sea. Much like you may head to the same side of the bed each night and snuggle into the you-shaped indent waiting for you there, limpets return to familiar spots on the rock face where they have carved out a space that perfectly fits their shell.
While limpets are exposed to the air and sunlight at low tide, they retain as much of their moisture as possible by forming a seal against the rock. Their conical shapes most likely evolved from the need to have the largest surface area available to create that seal.
Once the tide washes back over the limpets, they can return to their lives as mollusks that find food by scraping algae off the rocky seabed surfaces. This scraping requires a very strong set of teeth. If we had to drag our teeth across rock in order to remove our dinner, our teeth would be quickly ground to nubs.
Limpets, however, have a long spiral-like tongue called a “radula” that is covered in very tiny (less than 1 millimeter long), super strong teeth.
How Can Limpet Teeth Help Engineers?
The marine biologists studying limpets have discovered that their teeth consist of a scaffold of protein reinforced by densely packed nanofibers of the iron-based mineral goethite. As a general rule of engineering, the larger something is, the more opportunities there are for flaws. With so many tiny components packed closely together, the limpet teeth are nearly flawless.
Dr. Asa Barber and his team put this effective strength in numbers to the test by measuring the tensile strength of the limpet teeth, or how much stress they can withstand until stretching the teeth causes them to snap. They tested a dental sample that was 100 times thinner than a human hair and found it could withstand pressures up to 6.5 gigapascals, a measure of force per unit area. Dr. Barber compared the pressure his team put on the limpet teeth to holding up over 3,300 pounds (or 1,500 kilograms) of sugar on a single string of spaghetti.
For comparison, the previous record holding natural material, spider silk, usually can only withstand up to 1.3 gigapascals of pressure, although some exotic spiders have woven webs that can hold their own to around 4.5 gigapascals.
The limpet teeth even hold up to many human-made materials. Kevlar comes in at only 3-3.5 gigapascals, although graphine is still stronger. By studying the make-up of the limpet teeth, and learning how to reproduce their structural format of many tiny fibers packed together, engineers and scientists have the potential to form new materials that are both lighter and stronger. We could use these materials to make stronger cars, lighter aircraft, and maybe even stronger dental fillings for ourselves.
So, are you ready to trade in your teeth?
Until next time, this is Dr. Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.
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Raw limpets and group of limpets images courtesy of Shutterstock.