Impermeable Coating Material Inspired by Nacre

Innovation: Academia

University of Connecticut

2017

Image: Phil Shirley / Flickr / Some rights reserved

Protect From Fire

Depending on location, fire can be either predictable or unpredictable. In some areas, fires occur in cycles ranging from annual to hundreds of years. Where fire is cyclic, living systems must be able to not only survive fire, but to quickly recover following it. For example, pine trees that live in areas with periodic fires have thick bark that provides insulation, thereby protecting the tree’s living tissue.

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Manage Impact

An impact is a high force or mechanical shock that happens over a short period of time, such as a hammer hitting a nail rather than a hand pushing slowly against a wall. Because of their speed and force, impacts don’t allow materials to slowly adjust to the force, which can lead to cracks, ruptures, and complete breakage. Therefore, living systems have strategies that can absorb, dissipate, or otherwise survive that force without the need to add large amounts of material. For example, the Toco toucan’s large beak is very lightweight, yet can withstand impacts because it’s made of a composite material with rigid foam inside and layers of a hard, fibrous material outside.

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Manage Compression

When a living system is under compression, there is a force pushing on it, like a chair with a person sitting on it. When evenly applied to all sides of a living system, compression results in decreased volume. When applied on two sides, it results in deformation, such as when pushing on two sides of a balloon. This deformation can be temporary or permanent. Because living systems must retain their most efficient form, they must ensure that any deformation is temporary. Managing compression also provides an opportunity to lessen the effects of other forces. Living systems have strategies to help prevent compression or recover from it, while maintaining function. For example, African elephant adults weigh from 4,700 to 6,048 kilograms. Because they must hold all of that weight on their four feet, the tissues of their feet have features that enable compression to absorb and distribute forces.

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Coating from UConn is made of nanosheets in a polymer matrix that makes it nearly impermeable to air and other gases.

Benefits

Stronger
Eco-friendly
Scalable

Applications

Electronics
Packaging
Consumer goods

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure
Goal 12: Responsible Production & Consumption

The Challenge

Many electronics are susceptible to permanent damage from moisture. For example, the small components within cellphones require a waterproof barrier for protection. Making these small barriers is challenging, increasing the cost of the devices.

Innovation Details

The coating is made of a high concentration of nanosheets within a matrix. To make the coating, the nanosheets are pre-arranged in a series and the polymer flows between the sheets to lock them in place. The material forms the shape of the substrate it is laid on. It was shown to be 60 percent stronger than stainless steel and can be used on a variety of materials to protect from both fire and water.

Biomimicry Story

Nacre, or mother of pearl, forms the iridescent inner layer of the shells of some molluscs. It is a natural composite of plates of aragonite (a form of calcium carbonate) and natural polymers that coil around and through the plates. The polymer holds the plates together while allowing them to slip from side to side under stress, enabling the nacre to be both strong and flexible.

See Related Content

a macro image of a group of oyster brown, white, and black oyster shells

Biological Strategy

Protein Complex Guides Nacre Formation

Black-lip pearl shell

The protein, Pif, secreted by pearl oysters contributes to the strength and shape of the shell due to key amino acids that guide mineral crystal growth.

close up photograph of purple, blue, pink and green shell

Biological Strategy

Interlocking Increases Material’s Toughness

Mollusks (Snails, Octopuses)

Plates in nacre increase toughness by interlocking

Biological Strategy

Weak Interfaces Make Material Tough

Black-lip pearl shell

Layers of weak and stretchy organic material between brittle mineral layers in nacre make the whole composite tough by managing cracks.

References

Journal article

Biomimetic nanocoatings with exceptional mechanical, barrier, and flame-retardant properties from large-scale one-step coassembly

Science Advances

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