Sea Sponge’s “structural principles” inspire the “design strategy”

Sponges are among the earliest multicellular animals in the fossil record. They seem at first glance randomly organized, full of holes, asymmetrical, and devoid of complex organs. Yet one sea sponge in particular has secrets that make engineers drool with envy. The basket of flowers of Venus (Euplectella aspergillum) mastered fiber optics and force-absorbing building materials long before physicists and architects dreamed of.

Researchers at Brown University and the Wyss Center for Biologically-Inspired Engineering at Harvard University published an article in PNAS with new discoveries on this sponge:

Adapt has a wide range of physically demanding environmental conditions, biological systems have evolved a diverse variety of robust skeletal architectures. Such an example, Euplectella aspergillum, is a marine sponge living in sediment which is anchored to the seabed by a flexible bilge device made up of thousands of anchor spicules (long vitreous fibers resembling hair). Each spicule is covered with curled beards and has a internal architecture consisting of a solid core of silica surrounded by a assembly of coaxial silica cylinders, each separated by a thin organic layer. The thickness of each silica cylinder gradually decreases from the nucleus of the spicule to its periphery, which we to state a hypothesis is an adaptation to redistribute internal constraints, So increase overall strength of each spicule. [Emphasis added.]

The researchers devised a mathematical model of this concentric arrangement, seeing which sequence of radii and thicknesses would produce the maximum force transmission to the rest of the skeleton. Then they marked the sponge by their model:

Compared to the measurements of these parameters in the spicules of native sponges, our modeling results are remarkably well correlated, highlighting the beneficial character of that elastically heterogeneous lamellar design strategy. The structural principles obtained from this study thus provide potential design ideas for the manufacture of high strength beams for carrier applications via the modification of their internal architecture, rather than their external geometry.

When engineers design buildings, they usually think of the external geometry. Common examples are steel I-beam, truss, and buttress. What if the materials were designed from the inside out instead? Imagine how skyscrapers built on this “design strategy” could withstand earthquakes. A press release from Brown describes the habitat of the sponge:

Life can seem precarious for the sea sponge known as the Venus Flower Basket. Tiny, hair-like appendages made mostly of glass are all that holds the creatures to their homes on the seabed. But don’t be afraid for these creatures of the depths. These tiny lifelines, called basalia spicules, are sharpened for strength, according to new research by engineers at Brown University.

The news reveals the “Aha!” when a member of the engineering team examined the structure under an electron microscope:

When Haneesh Kesari, assistant professor of engineering at Brown, first saw this structure, it didn’t know what to think. But the pattern of decreasing thickness caught his attention.

It was not at all clear to me what this model was for, but it looked like a figure from a math book“Kesari said.” He had such a mathematical regularity to what I thought it must be for something useful and important to the animal. “

Kesari reunited with James Weaver and Joanna Aizenberg of the Wyss Institute for Biologically Inspired Engineering at Harvard, “who have been working with this species of sponge for years.” Years ago, the two discovered that the glass fibers in the flower basket of Venus act like perfect little strands of fiber optics, performing even better than those made by humans. Their 2004 article stated:

The spicules can work like single-mode, few-mode or multimode fibers, with thorns serving as light points along the spike stem. The presence of a lens-like structure at the end fiber increases its light collecting efficiency. Although free-space coupling experiments emphasize the similarity of these spicules to commercial optical fibers, the absence of birefringence, the presence of technologically inaccessible dopants in fibers, and their improved mechanical properties highlight the advantages of low temperature synthesis used by biology To build these remarkable structures.

So here, more than a decade later, another spectacular design feature of these microscopic fibers is brought to light. “The researchers say this is the first time to their knowledge that someone has evaluated the mechanical advantage of this particular arrangement diapers, ”the press release read. So these tiny little fibers that could so easily be dismissed by the casual viewer as “simple” or “primitive” actually perform two independent functions exceptionally well – light transmission and anchoring. It’s like watching a strong man pull a semi-truck and solve differential equations at the same time.

Remarkable conclusions

It is interesting how many times the word “remarkable” is used in the press release and the document. The fibers are “remarkably strong.” They have one “remarkable internal structure“giving them”remarkable properties. “The results of the mathematical model correspond to the actual sponge spicules”remarkably well. “Since this sponge is so remarkable, let’s add a few remarks.

All the scientific data, observations and models in these studies depend entirely on design thinking. Sponge spicules have a mathematical structure that refines them for two independent functions, which they perform to specifications that human engineers cannot yet achieve. Why on earth would these traits be attributed to blind operations of chance? Remarkably, this is what these scientists and journalists do:

The life of these sponges depends on their ability to remain attached to the seabed. They maintain themselves by filtering nutrients from the water, which they cannot do if they are thrown by the current. So that would make sense, thought Kesari, that natural selection can I have molded the spike anchors of the creatures into models of force – and the thickness model could be a contributing factor. [From the press release.]

More important again, many biological elements of the skeleton are inherently multifunctional and have evolved the ability to perform a variety of tasks in addition to their mechanical duties. [From PNAS.]

These are disposable products that hide the details. Useful lines are those that provide inspiration, insight and application through the observation of remarkable design. The press release ends:

It could add to the list of useful works of art inspired by nature.

In the world of engineering, you see all kinds of cases where the external geometry of a structure is changed to improve its specific strength – I-beams are one example, ”Monn said.“ But you don’t see a huge effort focused on the internal mechanical design of these structures. “

However, this study suggests that the spicules of sponges could provide a plan for load-bearing beams made stronger from within.

Add to this that the Venus flower basket is not unique. Other creatures, unrelated to evolution, produce similar patterns of refined strength, such as mother-of-pearl in oyster shells, fish scales, and the structure of our own bones and teeth. Conceptions of nature have led to institutes dedicated to the study of “biologically inspired design”.

How do you assess good science? Sir Francis Bacon said you would recognize it by its fruits. If inspiration, understanding and application are good fruits, intelligent design is ripe for the picking.

Image courtesy of NOAA’s Office of Ocean Exploration (NOAA) [Public domain], via Wikimedia Commons.

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