The significance of the structural principles of six rayed sponge spicules to the field of architecture

Six rayed sponge spicules, also known as glass sponge spicules, are complex glass skeleton systems grown by hexactinellid sponges, known for their ability to synthesize unusually long and highly flexible fibrous spicules. The system of six rayed sponge spicules and their constituent elements have been a useful model system for the design and manufacture of strong and damage-resistant structures.

The skeletal system of six rayed sponge spicules can be very complex, and the most famous six rayed sponge is a species of Euplectella, known as the "Venus basket", whose skeleton is built in a way that it can synthesize a diagonally reinforced cage-like skeletal tube, forming an elaborate lattice structure composed of periodic open and closed spaces. Each major load-bearing spicule in this species exhibits a unique layered structure consisting of concentric silica cylinders separated by thin organic interlayers that radiate outward from the inner silica solid core. The thickness of the concentric silica cylinders decreases toward the periphery of the spicules.

The spicules are encased in a layer of layered silicate cement, making the entire composite stiffer. This layered design strategy significantly increases the toughness of each spicule, and when cracks travel through the composite, they propagate in a step-like manner, with the thinnest outer layers significantly limiting how deep newly formed cracks can propagate.

Wyss Institute Core Faculty Member Joanna Aizenberg, PhD, and Wyss Senior Research Fellow James Weaver, PhD, in collaboration with Daniel Morse of the University of California, Santa Barbara, and Peter Fratzl of the Max Planck Institute of Colloids and Interfaces, have been studying six rayed sponge spicules for more than a decade, discovering structural and optical properties that can be used to improve structures, designs, and fiber optic technologies.

Now, a new paper co-authored by Aizenberg and Weaver in the Proceedings of the National Academy of Sciences reveals more secrets of the internal structural properties of glass sponges: the design pattern of concentric silica layers decreasing not only improves fracture resistance, but also increases the ultimate load-bearing strength of each spicule.

In collaboration with Brown University, the team successfully simulated the internal structure of the layered spicules and compared it with the layer measurements of more than a hundred sponge spicules to predict their load-bearing capacity under different loads. The team's results show that the layered spicule structure with concentric thickness decreasing has multiple functions designed to prevent damage accumulation before and after cracking.

The structural principles obtained in this study can be used to design and manufacture high-strength beams in load-bearing applications, opening up the possibility of new building design strategies for safer and more structurally sound materials by modifying their internal structure rather than their external geometry.

In short, six rayed sponge spicules have evolved into today's magical structure through millions of years of natural evolution, providing a reference for humans to use bionic technology to manufacture building materials, etc.