Iron teeth? With the unusual nickname “wandering meatloaf,” a reddish-brown mollusk found along rocky shores with hard, magnetic teeth seen only in rocks and not in a living organism. This has been the find. published in the journal Proceedings of the National Academy of Sciences in which they examined the giant Pacific chiton ( Cryptochiton stelleri ) , the world’s largest chiton, reaching up to approximately 35 centimeters long.
It is equipped with several dozen rows of teeth in a thin, flexible, tongue-like appendage that it uses to scrape rocks. Researchers at Northwestern University (USA) have discovered that these teeth are covered in magnetite, the hardest and most rigid biomineral known to date: it is up to three times harder than human enamel and mollusk shells.
“This mineral has only been observed in geological samples in very small amounts and has never been seen in a biological context before,” says Derk Joester of Northwestern, lead author of the study. “It has a high water content, which makes it strong with low density. We think this could harden the teeth without adding a lot of weight. “
The experts examined a Cryptochiton steller i tooth, using Mössbauer synchrotron spectroscopy from Argonne National Laboratory’s Advanced Photon Source, as well as transmission electron microscopy at Northwestern Atomic University and Nanoscale Experimentation and Characterization Center (NUANCE). They found santabarbaraíta scattered throughout the upper stiletto of the chiton, a long, hollow structure that connects the head of the tooth with the flexible membrane of the radula . Santabarbaraite is a hard mineral but it has less iron and more water than magnetite, which makes it less dense.
“It is a resistant material composed of extremely small nanoparticles in a fibrous matrix made of biomacromolecules , similar to the bones in our body,” the authors comment.
These nanoparticles help tooth bases vary in hardness and stiffness by at least a factor of two over distances of just several hundred microns – a few times the average width of a human hair.
This finding helps to understand how absolutely the entire tooth of the animal is designed to withstand chewing on rocks for food. Based on the minerals found in chiton teeth, the researchers developed a bio-inspired ink for 3D printing of ultra-hard, rigid and durable materials. Ink includes iron and phosphate mixed into a natural substance produced by chiton. When the ink dries, it creates a stiff material.
“We’ve been fascinated with the chiton for a long time,” explains Joester. “The mechanical structures are only as good as their weakest link, so it is interesting to learn how the chiton solves the engineering problem of how to connect your ultra-hard tooth to an underlying soft structure. ” This remains a major challenge in modern manufacturing So we look to organisms like chiton to understand how this is done in nature , which has had a waiting time of a couple hundred million years to develop. “
“We can continue to learn and develop materials inspired by the chiton, which connects ultra-hard teeth with a soft radula,” conclude the experts. In fact, these compounds could be used in soft robotics , to go where conventional robots cannot go due to their hard parts.
Referencia: Linus Stegbauer et al. 2021. Persistent polyamorphism in the chiton tooth: From a new biomaterial to inks for additive manufacturing. PNAS, in press; doi: 10.1073/pnas.202016011
