Tuesday, June 14, 2011

Glass skeleton

This is the skeleton of a venus' flower basket sponge (Euplectella aspergillum), that I bought in Stanley on our recent trip up north. These are amazing creatures, in various ways. Wikipedia says:
... the sponge symbiotically houses two small shrimp, a male and a female, who live out their lives inside the sponge. They breed, and when their offspring are tiny, the offspring escape to find a Venus Flower Basket of their own. The shrimp inside of the basket clean it, and in return, the basket provides food for the shrimp by trapping it in its fiberglass-like strands, and then releasing it into the body of the sponge for the shrimp. It is also speculated that the bioluminescent light of bacteria harnessed by the sponge may attract other small organisms which the shrimp eat.
I first heard of these things on Theodore Gray's fabulous website the Wooden Periodic Table Table. Among his roughly 150 samples representing silicon, is one of these. He has a simply beautiful QTVR of it - if you give it a little while to load, you can rotate it with the mouse. Go on - I'll wait here while you give it a try.

Gray writes of the skeletal structure;
This is a sea creature, a sponge of sorts, that grows a glass skeleton. That's right, the skeleton is made of what amounts to fiberglass. Isn't that the most amazing thing you've ever heard of? I suppose it shouldn't be any more amazing than us growing a calcium phosphate (actually calcium phosphate foam) skeleton, but it is to me. Not only is the skeleton glass, the fibers it's made of are said to be superior in some ways to man-made fiber optics, and of course they are grown at low temperatures, something people, as of this writing, have no idea how to do.
If that isn't enough amazement for you, consider the engineering properties of the skeleton. According to these boffins at Bell Labs,
Each of the structural levels corresponds to a fundamental construction principle commonly used in civil engineering and sometimes product design, but on a scale 1,000 times smaller than a building. For example, the fibers that comprise the sponge’s skeleton are arranged in a lattice, or open criss-cross pattern, reinforced by fibers that run diagonally in both directions inside alternate squares in the lattice. This construction technique is often found in high-rise buildings and free-standing bookshelves to counteract shear stress, which can easily collapse a non-reinforced square structure. The team also discovered that when the diameter of the sponge’s skeleton increases beyond a certain point the outer structure is reinforced by ridges in a spiral pattern. The ridges counteract an effect known as “ovalization,” which makes cylindrical structures more prone to collapse, as demonstrated by the fact that it’s fairly easy to twist or flatten an empty aluminum can. By stabilizing its skeleton with external ridges, the sponge makes itself difficult to crush. Other hierarchical levels include highly stable laminated glass beams, fiber-reinforced cements, and bundled structural elements, to name a few.
 So - pretty great eh? A bit better than a blurry photo of Winston's nose, anyway.

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