The secret to better folding phones might hinge on mussels

Date:
Thu, 22 Jun 2023 18:00:00 +0000

Description:
The shell of a cockscomb pearl mussel, which pops open thanks to a protein cushion and biological wires. Prof. Yu's Team Materials scientists are studying why these shellfish are so great at opening and closing. The post
The secret to better folding phones might hinge on mussels appeared first on Popular Science .

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The shell of a cockscomb pearl mussel, which pops open thanks to a protein cushion and biological wires. Prof. Yu's Team

The function of folding phones and handheld game consoles like the Nintendo 3DS hinges on, well, their hinges. Open and shut such gadgets enough times that the hinges start to fail, and you might find yourself wishing for a far better joint.

As it happens, the animal realm may have fulfilled that wish. Sources of inspiration take the form of bivalves: clams, oysters, cockles, mussels, and
a whole host of other two-shelled organisms. Over a bivalves life, its shells can open and shut hundreds of thousands of times, seemingly without taking damage.

Now, a team of biologists and materials scientists have worked together to examine the case of one particular bivalve, Cristaria plicata , the cockscomb pearl mussel. In their paper, published in the journal Science today, theyve not only reverse-engineered a mussels hinge, theyve recreated it with glass fibers and other modern materials.

Cockscomb pearl mussels, the studys starring bivalves, are found in fresh waters across northeast Asia. Ancient Chinese craftspeople grew pearls within this mussels shells. By opening the mussel, inserting a small object like a bead or a tiny Buddha inside, closing the animal, and letting it be for a year, they could retrieve the object afterwardnow coated in iridescent mother-of-pearl.

Mother-of-pearl, also known as nacre, has long drawn the attention of materials scientists for far more than its beauty. Although nacre is made
from a brittle calcium carbonate mineral called aragonite, its structurearagonite bricks glued together by a protein mortargives the substance incredible strength and resilience .

A lot of researchers have replicated various aspects of its brick-and-mortar structure to try to create stiff, tough, and strong materials, says Rachel Crane , a biomechanist at the University of California, Davis, who was not an author of the new paper.

[Related: This new material is as strong as steelbut lighter ]

In the process of studying nacre, some scientists couldnt help notice the mussels hinge. Despite also being made from the same brittle aragonite, the hinge both bends and stretches without breaking. This exceptional performance impressed us greatly, and we decided to figure out the underlying reason,
says Shu-Hong Yu , a materials scientist at the University of Science and Technology of China, and one of the papers authors.

Biologists had studied hinges and the differences between them to classify bivalve species as early as the 19th century. But they didnt have the technology to peel apart these living joints inner structures. Yu and his colleagues, though, extracted the hinges and examined them under a battery of microscopes and analyzers.

They found that the bivalves hinge consists of two key parts. The first is at the hinges core: a folding part shaped like a paper fan. The fans ribs are an array of tiny aragonite wires, shrouded in a soft protein cushion. The second part is a ligament, an elastic layer over the fans outer edge.

As the hinge closes, the protein matrix helps keep the wires straight, preventing them from bending and breaking. Meanwhile, the outer ligament absorbs the tension from the hinge unfurling. Together, this configuration makes the hinge particularly hardy.

The authors placed hinges extracted from mussels in a machine that repeatedly forced them open and shut. This tested their prowess under long-term,
repeated stress. Even after 1.5 million cycles, the authors found no sign of damage. In other words, if the mussel opened and shut its shells once a minute, every minute, for three years on end, its hinge would stay perfectly functional.

This makes the mussels hinge super-resistant to what engineers call fatigue. Everything from nuts and bolts to bridge supports builds up wear and tear
from repeated use, just as your legs might feel tired if youve recently run a marathon. And, just like a pair of exhausted legs, a fatigued part is more likely to failwith crippling consequences. The bivalve shell hinge is particularly interesting not only for its fatigue resistance, but also for
its ability to bend, says Crane.

Its surely tempting to imagine bizarre biopunk doors that open and close on the backs of indefatigable mussel hinges. While thats almost certainly impractical, the authors believe that these hinges could inspire human-engineered parts that serve our purposes well.

[Related: Recycling one of the planets trickiest plastics just got a little easier ]

In fact, inspired by the structure they found, Yu and his colleagues
fashioned their own hinge from glass fibers embedded like fan ribs in a polymer matrix. They put their artificial hinge to the test, and found that
it held up like the genuine, organic articlewhile other hinges, one with disorganized glass fibers and another with glass spheres, began to break and crack

Yu says that their early effort isnt meant for regular human use. But it demonstrates that we could create a mussel-like bend if we needed to. For instance, what if a mobile phone designer wants to make a folding
touch-screen phone that needs a brittle material like glass?

The fan-shaped-region-inspired design strategy provides a promising way to address this challenge, Yu says. His group now plans to examine what those soft proteins do in the hinge.

But evolution and engineering play by different rules. It isnt necessarily easy to emulate materials that have evolved over millions of years. The finest-scale patterns in biological structures are often challenging and costly to replicate, says Crane.

The post The secret to better folding phones might hinge on mussels appeared first on Popular Science . Articles may contain affiliate links which enable us to share in the revenue of any purchases made.



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Link to news story:
https://www.popsci.com/science/mussels-hinge-engineering/


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