Seashells or spider silk: how nature could transform the structure of cities

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Seashells or spider silk: how nature could transform the structure of cities
British architect Jack Munro proposed a city in Egypt built from bricks made of sand and animal blood

In the race to replace concrete and steel, bioengineers and architects are experimenting with alternatives including blood, bone and eggshells

Ask the Cambridge bioengineer, Michelle Oyen, how the cities of the future might look, and she’ll reference termite mounds, along with the swirling architecture of Antoni Gaudí, whose buildings look like they’ve grown from organic matter rather than been built by human hands. Oyen and her contemporaries are currently striving to harness nature’s smart building techniques, investigating bone, eggshell, seashells and spider silk, as alternatives to unsustainable steel and concrete.

“As engineers,” she says, “we throw energy at problems to make things technologically better, but we don’t necessarily think about the consequences of what all of that energy input is doing.” The concrete industry, for example, produces 5% of global CO2 emissions. The beauty of the materials that Oyen and colleagues are developing is that they can be produced in gentle, low-energy conditions.

Eggshell is her favourite example. “If you look at a chicken, they go from zero to eggshell in 18 hours. It’s almost a millimetre thick, 95% ceramic, and it has this organic component that makes it very tough. The whole thing has been put down in an extremely short period of time, at an ambient pressure and at body temperature, barely above ambient temperatures.”

Manmade ceramics, on the other hand, are formed at thousands of degrees Celsius. The ceramic deposits on the protein in the eggshell membrane, and the protein’s presence makes it more durable than manmade ceramic. “So you have this paradigm,” says Oyen, “where nature does these things cleverly, using information, whereas engineers just throw energy at them.” […]

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