Strong glass and fiber-optics occuring in nature

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The tube, tapered to a close at one end and festooned with a cluster of curious white fibers at the tip, resembles an upturned dog’s tail. It is, in fact, the skeleton of a deep-sea sponge, she reveals, made entirely out of a natural glass. The tube acts as a kind of high-rise apartment building for shrimp that live symbiotically in the sponge’s tissue.

The glass, drawn thinly into lacy threads, looks astonishingly fragile for a structure that withstands thousands of pounds of pressure per square inch at depths exceeding 500 meters below the ocean surface.

Aizenberg agrees. “It’s incredibly strong — but why? What mechanical principles make this particular design work so well?”

As the Gordon McKay Professor of Materials Science in Harvard’s School of Engineering and Applied Sciences, one of Aizenberg’s current projects is to use synthetic materials to model and modify the sea-sponge structure. Tinkering with the glass lattice design allows her to see exactly what each geometric element — whether it is the tube’s foundational mesh of squares with diagonals, or its helical external ridges — contributes to the strength and flexibility of the whole.

“Nature builds structures, and it builds them better than we do. There are new design principles to be taken from nature. My job,” says Aizenberg, the Susan S. and Kenneth L. Wallach Professor at the Radcliffe Institute for Advanced Study, “is to find out what they are and how to use them.”

Finding natural structures to study is the first order of business, and much of the initial stage of Aizenberg’s research sounds like a good ocean-side summer holiday in disguise: rummaging in bins and dark corners of curiosity shops, beachcombing, and even snorkeling.

As a Ph.D. student in Israel, Aizenberg went on regular diving expeditions in the Red Sea, collecting whatever she could from the sea floor. When she’s at the beach, she keeps an eye out for shells with unusual changes in their design.

Her analytical instinct in this regard is as restless as her search. “I try to think of what’s responsible for the change,” she says, “whether it’s a protein or the local salinity, or even a mechanical principle that might result in some interesting aberration.”

Sometimes the search for specimens can be as revealing as the analysis itself. When Aizenberg found the sea sponge in a curiosity shop, it had been lying in a dark corner on the lowest shelf.

“It was unusually bright — surprisingly bright, which gave me the idea that these hairs on the end are optical fibers that light up the whole structure,” she says. “We think we just now invented fiber optics for telecommunications, but this sponge has benefited from it for millennia.”

The sponge, she speculates, uses the fibers for its own communication purposes: The fibers direct light from bioluminescent bacteria into the glass structure. Small deep-sea organisms flock to the glowing glass — a useful perk in a low-food-density zone for preying shrimp. ...

It's amazing how perfect these things are, isn't it?