An area of a radula from Crytochiton stelleri, revealing its tough, resilient teeth. Credit: Northwestern University
Rare Mineral From Rocks Found in Mollusk Teeth
Northwestern University scientists have, for the very first time, found an unusual mineral concealed inside the teeth of a chiton, a big mollusk discovered along rocky shorelines. Before this unusual surprise, the iron mineral, called santabarbaraite, just had actually been recorded in rocks.
The brand-new finding assists comprehend how the entire chiton tooth — not simply the ultrahard, resilient cusp — is developed to sustain chewing on rocks to feed. Based on minerals discovered in chiton teeth, the scientists established a bio-inspired ink for 3D printing ultrahard, stiff and resilient products.
“This mineral has only been observed in geological specimens in very tiny amounts and has never before been seen in a biological context,” stated Northwestern’s Derk Joester, the research study’s senior author. “It has high water content, which makes it strong with low density. We think this might toughen the teeth without adding a lot of weight.”
The research study will be released today in the Proceedings of the National Academy of Sciences.
Scanning electron microscropy picture of chiton teeth.
Joester is an associate teacher of products science and engineering in Northwestern’s McCormick School of Engineering and a member of the Chemistry of Life Processes Institute. Linus Stegbauer, a previous postdoctoral fellow in Joester’s lab, is the paper’s very first author. At Northwestern throughout the research study, Stegbauer is now a primary detective at the Institute of Interfacial Process Engineering and Plasma Technology of the University of Stuttgart in Germany.
Rendering of a virtual area of a single tooth head and upper stylus, created from a 3D restoration as figured out by synchrotron microcomputer tomography. Credit: Northwestern University
One of the hardest recognized products in nature, chiton teeth are connected to a soft, versatile, tongue-like radula, which scrapes over rocks to gather algae and other food. Having long studied chiton teeth, Joester and his group most just recently relied on Cryptochiton stelleri, a giant, reddish-brown chiton that is often passionately described as the “wandering meatloaf.”
To take a look at a tooth from Cryptochiton stelleri, Joester’s group worked together with Ercan Alp, a senior researcher at Argonne National Laboratory’s Advanced Photon Source, to utilize the center’s synchrotron Mössbauer spectroscopy in addition to with Paul Smeets to utilize transmission electron microscopy at the Northwestern University Atomic and Nanoscale Characterization and Experiment (NUANCE) Center. They discovered santabarbaraite distributed throughout the chiton’s upper stylus, a long, hollow structure that links the head of the tooth to the versatile radula membrane.
“The stylus is like the root of a human tooth, which connects the cusp of our tooth to our jaw,” Joester stated. “It’s a tough material composed of extremely small nanoparticles in a fibrous matrix made of biomacromolecules, similar to bones in our body.”
Joester’s group challenged itself to recreate this product in an ink developed for 3D printing. Stegbauer established a reactive ink consisting of iron and phosphate ions blended into a biopolymer stemmed from the chitin. Along with Shay Wallace, a Northwestern college student in Mark Hersam’s lab, Stegbauer discovered that the ink printed well when combined right away prior to printing.
Mouth and extending anterior end of radula. Credit: Northwestern University
“As the nanoparticles form in the biopolymer, it gets stronger and more viscous. This mixture can then be easily used for printing. Subsequent drying in air leads to the hard and stiff final material,” Joester stated.
“Mechanical structures are only as good as their weakest link, so it’s interesting to learn how the chiton solves the engineering problem of how to connect its ultrahard tooth to a soft underlying structure.”
— Derk Joester, products researcher
Joester thinks we can continue to gain from and establish products influenced by the chiton’s stylus, which links ultra-hard teeth to a soft radula.
“We’ve been fascinated by the chiton for a long time,” he stated. “Mechanical structures are only as good as their weakest link, so it’s interesting to learn how the chiton solves the engineering problem of how to connect its ultrahard tooth to a soft underlying structure. This remains a significant challenge in modern manufacturing, so we look to organisms like the chiton to understand how this is done in nature, which has had a couple hundred million years of lead time to develop.”
3D printing of bio-inspired composites. Credit: Northwestern University
The research study, “Persistent polyamorphism in the chiton tooth: From a new biomaterial to inks for additive manufacturing,” was supported by the National Science Foundation (award numbers DMR-1508399 and DMR-1905982), National Institutes of Health (award number NIH-DE026952), Air Force Research Laboratory (award number FA8650-15-2-5518) and Deutsche Forschungsgemeinschaft (award number STE2689/1-1).
