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article imageNew insight into the strength of sea sponges

By Tim Sandle     Apr 8, 2015 in Science
The hair-like appendages that hold a sea sponge to the sea bed are fine-tuned for strength. The findings about the super-strong fibers could inform engineers about making load-bearing structures.
That engineering can learn from sea sponges isn’t as strange as it first seems. The tiny, hair-like appendages, called basalia spicules, that fix the creature to the floor are composed of a form of glass (silica). Scientists have been keen to find out what the secret is to the spicules' strength.
Sponges are animals of the phylum Porifera. Sea sponges fix themselves to the floor so that they can feed. Being in this position allows them to filter food. This is something that they could not do if they were free-floating. The multicellular organisms have bodies full of pores and channels, which allows water to circulate through them and for the animal to capture microscopic food.
New research indicates that the strength is due to the internal structure of the appendages. The spicules are only 50 microns in diameter, have a central core that is surrounded by between 10 to 50 concentric cylinders of glass. Each of these cylinders is separated by a very thin layer of an organic material. To provide structural support, the walls of each cylinder decrease in thickness moving outwards from the core toward the outside edge of the spicule. It is this pattern of decreasing thickness that is key.
Scientists found that the structure has a mathematical regularity. This led to a research team constructing their own mathematical models. Through this they found out that the organic layers between the glass cylinders allowed the cylinders to slide against each other. This enabled the sponge to harness its maximum load capacity.
Furthermore, it was found that the arrangement and thicknesses of the different layers was the main contributor to the spicules' strength.
This study, however, suggests that sponge spicules could provide a basis for load-bearing beams made stronger from the inside out. This would be useful in building construction.
The study has been conducted by researchers from Brown University. The findings have been published in the journal PNAS, in a research paper titled “New functional insights into the internal architecture of the laminated anchor spicules of Euplectella aspergillum.”
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