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At the bottom of the Pacific Ocean, cylindrical clusters of Euplectella aspergillum glass sponge jut up like skyscrapers into the depths of the sea. Some are home to tiny shrimp, for which an 11-inch sponge is essentially a skyscraper. And the glass skeleton of the sponge is certainly an architectural feat, made up of a geometric lattice that gives the sponge the illusion of being wrapped in lace. Yet it is enduringly robust, able to stay rooted in the seabed and weather currents without breaking or shattering.
Such structural superpowers leave many scientists eager to unlock the secrets of this crystalline sponge. The answers could solve engineering problems, such as designing a large building that will not collapse in strong winds. A study published Wednesday in the Journal of the Royal Society Interface reveals how the ridges in the sponge’s skeleton suppress a destructive phenomenon called a vortex, which can cause catastrophic damage to structures like chimneys and chimneys.
“These works support the idea that the dynamic properties of the fluids of glass sponges could be no less remarkable than their structural characteristics,” wrote Giacomo Falcucci, a mechanical engineer at Tor Vergata University in Rome, who was not involved in research, in an e-mail.
Under the soft tissue of the glass sponge, a tubular skeleton protects and supports the animal. The central skeleton comprises bundles of necessary shapes called spicules which are oriented vertically, horizontally and diagonally and merged into a lattice structure that looks somewhat like a checkerboard. Around this network are protruding clockwise and counterclockwise helical ridges that resemble a series of fire escapes wrapped around the tubular sponge and under its fabric. All together, the ridges look like a maze.
“It has this very dense, highly consolidated system,” said James Weaver, senior scientist in the School of Engineering and Applied Sciences at Harvard University and author of the new article. The study was also conducted by Katia Bertoldi and Matheus Fernandes, researchers from the same school.
Dr Weaver began studying Euplectella aspergillum in the early 2000s. He initially focused on sponge skeletons, studying their various structures and mechanical properties.
For this article, the researchers looked at the sponge from a hydrodynamic perspective: how fluids act and move around its skeleton.
They pursued this question after noticing that the ridges of the sponge eerily resembled helical strakes, ridge-like protrusions often used to protect the structural integrity of towers and other cylinders. When a fluid such as air moves around a smooth cylinder, vortices are given off alternately from side to side on the leeward side of the cylinder. These alternating vortices can cause the cylinder to vibrate, causing noise and safety issues. In human architecture, helical strakes suppress vortices by disrupting the flow around the structure.
To understand whether the outer ridges of the glass sponge offered a similar hydrodynamic advantage, the researchers created a series of mechanical and computer models to visualize how the anatomy of the sponge affects the flow of surrounding fluids.
Their models showed that the sponge’s maze of ridges completely eliminated vortex loss. “What we find in the structure of the sponge is that it is able to remove it completely, rather than just delay or decrease it,” Fernandes said. One obvious application of the new research would be to design helical strakes inspired by sponges.
The authors hypothesize that this very complex skeleton helps keep the sponge anchored in the soft sediments of the seabed, which could be excavated by the swirling vortices. “The sponge could be crutch,” Dr. Weaver said.
“This sponge skeleton fascinates materials scientists,” wrote in an email Sally Leys, an invertebrate zoologist at the University of Alberta who was not involved in the research. “However – a big one though – they still neglect the animal’s tissues.”
Unlike previous research that only looked at the sponge skeleton, the new paper includes several models that attempt to reconstruct the soft, porous tissue of a living sponge.
To Dr. Leys, some of the models in the new paper that show flow through a porous sponge are unrealistic. “Water does not passively move through a glass sponge,” said Dr. Leys. “They control the flow.”
Ocean sponges use an internal pump to channel water to nanometer-sized openings where food and oxygen are exchanged and waste is excreted, then the water exits through other pores and eventually comes out. the top of the sponge, explained Dr Leys.
Dr Leys also found that the amount of flux the researchers chose to simulate around the sponge was “extremely unrealistic” as it was far greater than the highest flux a living Euplectella could experience, he said. she declared.
The researchers admitted that not all of their models were designed to mirror a living sponge in the wild. Instead, they simulated high flow rates to demonstrate the potential utility of the spongy structure for engineering.
Dr Leys is concerned that the models are misleading. “The true biology of these exotic animals needs to be taken into account a lot more by materials scientists,” she said.
While the precise vortex-suppressing qualities of living glass sponges may remain a mystery, the researchers’ findings shed light on the use of the internal skeleton as a proxy for man-made structures.
“It’s important to realize the power of drawing inspiration from nature,” Fernandes said.
In such a future, our terrestrial chimneys might start to look much more like a bustling metropolis of shrimp in the deep sea.
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