Building Material Inspired by Marine Sponges

Innovation: Academia

Harvard

2020

Image: Dmitry Grigoriev / Shutterstock / CC BY SA - Creative Commons Attribution + ShareAlike

Manage Mechanical Wear

A living system is subject to mechanical wear when two parts rub against each other or when the living system comes in contact with abrasive components in its environment, such as sand or coral. Some abrasive components are a constant force, such as finger joints moving, while others occur infrequently, such as a sand storm moving across a desert. Living systems protect from mechanical wear using strategies appropriate to the level and frequency of the source, such as having abrasion-resistant surfaces, replaceable parts, or lubricants. For example, human joints like shoulders and knees move against each other all day, every day. To protect from mechanical wear, a lubricant reduces friction between the cartilage and the joint.

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Prevent Buckling

When a living system undergoes compression to the extent that it causes structural damage, it results in buckling. For example, if a person pushes down on the top or the side of a paper cup, the cup’s wall will eventually give way, or buckle. Although a living system could add material to strengthen a structure, this requires expending precious energy. Instead, it must use energy and materials conservatively to avoid buckling, strengthening structures through careful placement of materials to resist, absorb, or deflect compressive forces. For example, instead of one long, tubular stem, some plants like bamboo have stronger nodes scattered along their stems. When compressed, these nodes keep the round stems from taking on an oval shape that weakens the structure and could result in buckling.

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Prevent Deformation

When a living system undergoes compression, tension, shear, bending, or twisting, its internal inter-molecular forces can often resist these forces and even change shape temporarily, returning to the original shape when the forces stop. However, if the force is too strong or lasts too long, permanent deformation or structural failure can occur, resulting in death. Therefore, living systems have strategies to resist deformation or help ensure limited deformation. For example, bones have thin crystals and proteinaceous fibers that provide strength and flexibility, protecting them from forces that would otherwise cause deformation on a daily basis.

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Prevent Fracture/Rupture

High force impact or stress can cause materials that comprise living systems to separate into two or more pieces (called fracturing) or to break or burst suddenly (called rupturing). For example, a scallop prevents structural failure from fracture because its shell is comprised of two materials of varying stiffness. When a crack moves from the scallop’s stiff material to the less stiff one, the latter reduces the force at the tip of the crack, thereby stopping it from spreading farther.

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Structural material from Harvard University has a diagonally-reinforced square lattice structure that makes it strong and lightweight.

Benefits

Increased strength
Increased durability
Reduced materials
Lightweight

Applications

Building materials
Architecture

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure
Goal 11: Sustainable Cities & Communities

The Challenge

Buildings and bridges are usually made of very rigid materials such as concrete and steel. When an earthquake or other natural disaster hits, the inflexible structure can crack or break. If structural damage occurs, the repairs can be costly, or could lead to catastrophic failure of the overall structure.

Innovation Details

The material has a diagonally-reinforced square lattice-like skeletal structure, inspired by the Venus’ flower basket. The diagonal reinforcement increases the material’s resistance to buckling or breaking under a large force. The structure also has a high strength-to-weight ratio, meaning it can withstand heavy forces with less material than a typical lattice structure.

Biological Model

The Venus’ flower basket lives anchored to the deep ocean floor. Also known as glass sponges, their cylindrical skeletons are made out of silica, the main component of glass. The silica is arranged in concentric layers known as spicules. The spicules are arranged into a tube-shaped square lattice. Two separate but overlapping lattices make up the main frame, and because these lattices can still move relative to one another, the skeleton can be flexible while it’s growing. The squares of the lattice are reinforced by struts that run vertically, horizontally, and diagonally. These struts are made of bundles of spicules and further support the lattices against bending, sliding, and twisting forces.

See Related Strategy

Biological Strategy

Glass Skeleton Is Tough Yet Flexible

Venus's flower-basket

The silica skeleton of the Venus’s flower-basket sea sponge is tough and stable because multiple levels of organization each help to manage forces.

References

Journal article

Mechanically robust lattices inspired by deep-sea glass sponges

Nature materials

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