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How ‘Wandering Meatloaf’ Has Its Teeth So Hard

The gumboot chiton is not a charming creature. Massive mollusks creep along the waters of the Pacific coast. Haul up and down the coastline. Sometimes it is unreasonable to know that But the chiton’s unassuming body hid rows of tiny but majestic teeth, which creatures use to scrape algae from rocks. It is the hardest material known to exist in living things.

Now, a team of scientists has discovered a surprising ingredient in chiton’s hard teeth: a rare iron-rich mineral previously only found in real rock. Researchers reported Monday in the journal PNAS that the tiny particles of minerals that are strong but lightweight Helps to harden the teeth of mollusks

The discovery could help engineers design new types of materials. according to scientists which provides proof of principle by creating chiton-inspired ink for 3D printers.

The chiton feeds by sweeping its flexible, ribbon-like tongue, called a radula, along algae-covered rocks. The extra-hard teeth line the soft radula. A long hollow tube called a stylus. Attach each tooth to the redula.

Scientists have previously discovered that the tops of chiton teeth contain an iron mineral called magnetite. But little is known about the composition of the stylus. “We know there is iron in the top of the tooth,” said Linus Stegbauer, a materials scientist at the University of Stuttgart in Germany. “But in the root structure We don’t know what happened in there.”

In this new study The researchers analyzed chiton teeth using a variety of advanced imaging techniques. including many types of spectroscopy This allows scientists to learn about the chemical and physical properties of materials by observing how they react with light and other electromagnetic radiation.

They found that the stylus contained tiny particles of some kind of iron ore suspended in a softer matrix. (Matrix contains chitin which are compounds that make up the exoskeleton of insects and crustaceans)

After further analysis They were stunned to find that the mineral particles were santa barbarite. which are minerals that have never been seen in living things before “It was a surprise as a whole. And then they keep coming in,” said Derk Joster, senior author and materials scientist at Northwestern University.

Santa Barbarite is a hard mineral. But it has less iron and more water than magnetite. which makes it less dense Minerals may allow chitons to build strong, lightweight teeth while reducing their dependence on iron. “Steel is a physiologically scarce material,” says Dr. Joster.

The researchers also discovered that santa barbarite particles were not evenly distributed throughout the stylus. but was concentrated at the top closest to the tooth surface and scattered at the bottom where the stylus is connected to the soft redula This scatter pattern creates a gradient. This makes the stylus stiffer and stiffer at the top and more flexible at the bottom.

“Living organisms have enormous spatial control over where minerals go,” said Dr. Joster. “And that’s what made us think about how to use it to create the material. If living beings could simulate this Can we do the same?”

Researchers decided to try and create a new 3D printer “ink” inspired by chiton teeth. They started with a chitin-like compound and then added two liquids: one containing iron and the other containing phosphate. Mixing the ingredients together produces a thick paste with tiny particles. “Then it’s ready to print – you can transfer it to your 3D printer,” says Dr Stegbauer.

Ink hardens when it dries. But the final physical properties depend on the amount of iron and phosphate added to the mixture. the more you fill The more nanoparticles, the more they form. And the final material becomes harder and harder. by adjusting the formula in this way Researchers have been able to create flexible, rubbery objects like squids. or hard and hard like bone

“The ink should be mixed in a ratio that you can change immediately before printing,” says Dr. Joster. “And that will allow you to change the composition. nanoparticle quantity and the strength of the material immediately This means that you can print materials that vary greatly in strength over relatively short distances.”

This technique could be useful in the expanding field of soft robotics. This allows engineers to build rigid and rigid machines in certain places. And it is soft and flexible in other parts, Dr. Joster said. “I think it would be wonderful if you could print the whole job. of these gradations into the structure.”

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