Marine sponges could inform structure of future buildings

In a paper published in Nature Materials, the researchers showed that the diagonally-reinforced square lattice-like skeletal structure of Euplectella aspergillum has a higher strength-to-weight ratio than the traditional lattice designs that have been used for centuries in the construction of buildings and bridges.

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"We found that the sponge's diagonal reinforcement strategy achieves the highest buckling resistance for a given amount of material, which means that we can build stronger and more resilient structures by intelligently rearranging existing material within the structure," said Matheus Fernandes, a graduate student at Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and first author of the paper.

"In many fields, such as aerospace engineering, the strength-to-weight ratio of a structure is critically important," said James Weaver, a Senior Scientist at SEAS and one of the corresponding authors of the paper. "This biologically-inspired geometry could provide a roadmap for designing lighter, stronger structures for a wide range of applications."

Diagonal lattices in structures use small, closely spaced diagonal beams to evenly distribute applied loads. This geometry was patented in 1820 by the architect and civil engineer, Ithiel Town.

"Town developed a simple, cost-effective way to stabilise square lattice structures, which is used to this very day," Fernandes said in a statement. "It gets the job done, but it's not optimal, leading to wasted or redundant material and a cap on how tall we can build. One of the main questions driving this research was, can we make these structures more efficient from a material allocation perspective, ultimately using less material to achieve the same strength?"

To answer this question the team looked to Euplectella aspergillum’s tubular body, which employs two sets of parallel diagonal skeletal struts that intersect and are fused to an underlying square grid.

"We've been studying structure-function relationships in sponge skeletal systems for more than 20 years, and these species continue to surprise us," said Weaver.

In simulations and experiments, the researchers are said to have replicated this design and compared the sponge's skeletal architecture to existing lattice geometries. The sponge design outperformed them all, withstanding heavier loads without buckling. The researchers showed that the paired parallel crossed-diagonal structure improved overall structural strength by over 20 per cent, without the need to add additional material.

"Our research demonstrates that lessons learned from the study of sponge skeletal systems can be exploited to build structures that are geometrically optimized to delay buckling, with huge implications for improved material use in modern infrastructural applications," said Katia Bertoldi, the William and Ami Kuan Danoff Professor of Applied Mechanics at SEAS and a corresponding author of the study.