The sea urchin spines are mostly made of calcite, usually a very brittle and fragile material. In the case of the sea urchin, however, the spines are much more durable than the raw material alone. The reason for its strength is the way that nature optimises materials using a brick wall-style architecture. Scientists at the University of Konstanz have used the sea urchin pattern to synthesise cement at the nano-level.
“Our cement, which is significantly more fracture-resistant than anything that has been developed thus far, provides us with completely new construction possibilities”, Professor Helmut Cölfen, leader of the study, says. “A pillar made of this cement could be built 8,000 metres high, or ten times as high as the current tallest building in the world, before the material at its base would be destroyed by its weight. Normal steel, which has a value of 250 megapascals, could only reach 3,000 metres in height.”
A thin section of sea urchin spine reveals the structural principle: crystalline blocks in an orderly structure are surrounded by a softer amorphous area. In the sea urchin’s case, this material is calcium carbonate. Cement itself has a disordered structure – each component sticks to all the others. This means that in order for cement to truly profit from the increased stability provided by brick and mortar construction, its structure has to be reorganised at the nano-level.
See urchin spines and mussel shells are made of calcite, because large quantities of calcium are available in water. Helmut Cölfen explains: “People have much better construction materials than calcite. If we succeed in designing the structures of materials and reproduce nature’s blueprints, we will also be able to produce much more fracture-resistant materials – high-performance materials inspired by nature”.
Photo credit: Tim Nicholson