Flexible and foldable devices have been the recent norm in technology. As more foldable devices appear in human lives, users seek long-term service where the folded parts can endure the damage of repeated deformation.
Screen cracks in smartphones are occasional occurrences that can happen for several reasons. Contrary to popular belief that scratch shatters the screen, the reasons include little falls, dropping heavy objects, or sitting on the phone. Once the smartphone screen is damaged, the quality of the display and the phone's ability to perform everyday functions are affected.
Saving the Screens from Cracks
A group of biologists and material scientists joined to investigate the potential of cockscomb pearl mussels (Cristaria plicata) in preventing brittle fracture. Lead author Professor Yu Shuhong from the University of Science and Technology of China proposed the development of smash-proof screens using the combination of design and materials inspired by the resistance of seashells against fatigue damage.
As early as the 19th century, biologists have already studied the nature of mussel hinges. Still, they do not have the right technology to investigate the inner structures of these living joints. Yu and his team could extract and analyze the hinges under microscopes and analyzers.
The researchers found out that the toughness of the bivalve's hinge relies on its core and an elastic ligament layer. From this discovery, Yu and his colleagues developed their hinges from glass fibers embedded in a polymer matrix like fan ribs.
After testing their artificial hinge, they observed that it could hold up like its natural counterpart while other versions of hinges started to break and crack. Shuhong believes their discovery can also be applied in other industries, such as aerospace and tissue engineering.
READ ALSO: Why Did the World's Largest Mollusk Grew Excessively?
Why are Molluscan Shells Resistant to Damage?
Oysters, scallops, mussels, and clams build an external shell made of a pair of domed valves joined together by a hinge. The valves open when the animal needs to feed and reproduce and close when it faces any safety threat.
The shells of mollusks are composed of 95% chalk which is known for being very brittle when present in its pure form. Even after 1,500,000 cycles, the tissue can still function without showing signs of fatigue behaviors. The inner shells are coated with nacre, a complex crystalline substance made of alternating layers of organic materials film. These layers act like miniature Lego blocks, making the shells extremely strong and tough. Because of its high flexibility, the nacre allows the shell to resist the impacts of repeated opening and closing without getting fractured.
Through microscopic observations, the scientists discovered the unique properties of its hinge using a structure that looks like a folding fan. Meanwhile, the ribs are aragonite produced from organic and inorganic substances. The aragonite contains hard nanowires that help provide rigidity and allows the distribution of stresses toward the circumference of the hinge. The twinning planes that develop in crystals strengthen the hinge. As the valve opens and closes, a soft matrix absorbs the compressive and shear stresses.
"The folding fan-shaped region in the hinge can sustain large deformation during repetitive opening-and-closing valve motions and maintain its structure and function for a long period," said Shuhong.
Meanwhile, the muscles inside the shell allow the mollusk to pull the valves together, ensuring the organism's safety as it closes.
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