Innovative Marine Coating Inspired by the Salvinia Water Fern

Innovation: Industry

AIRCOAT project

Image: Le.Loup.Gris / Wikimedia / CC BY SA - Creative Commons Attribution + ShareAlike

Protect From Dirt/solids

When dirt and other small solids adhere to living systems, they can slow them down, create blockages, reduce their ability to carry out vital functions, or cause surface wear and tear. Due to electrostatic forces, it’s easy for dirt and other solids to adhere to surfaces, so living systems must overcome those forces. An earthworm, for example, uses a small electric current to keep soil particles from adhering to its body as it moves through the soil. This enables it to move more efficiently by reducing drag.

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Protect From Excess Liquids

While water is essential to life, too much water or other liquids can overwhelm living systems. Excess liquids can, for example, decrease a living system’s access to oxygen, promote excessive bacterial or fungal growth, or strip away soil and nutrients. To prevent the accumulation of excess liquids, living systems must control the movement of liquids across their boundaries or surfaces. They do so using waterproofing materials or structures, slowing flow, and/or facilitating flow to move the liquid away. Plant leaves, for example, commonly have waxy surfaces comprised of water-repelling chemicals to keep water from engorging the leaves or facilitating bacterial and fungal growth.

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Protect From Microbes

In living systems, microbes play important roles, such as breaking down organic matter and maintaining personal and system health. But they also pose threats. Bacteria can be pathogens that cause diseases. Some bacteria create colonies called biofilms that can coat surfaces, reducing their effectiveness–for example, inhibiting a leaf’s ability to photosynthesize. Living systems must have strategies for protecting from microbes that cause disease or become so numerous that they create an imbalance in the system. At the same time, living systems must continue living in harmony with other microbes. Some living systems kill microbes. Others repel without killing to reduce the chances that microbes will adapt to the lethal strategy and become resistant to it. For example, some pea seedlings exude a chemical that inhibits biofilm buildup.

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Protect From Fungi

Fungi–which include molds and mushrooms, amongst others–play important roles in every ecosystem, but can also create diseases in plants and animals. Fungi can rapidly reproduce, so living systems must fend them off early to avoid their spread and potential, physical harm. Living systems use both physical and chemical strategies to protect from fungi, and must ensure that these strategies don’t harm the threatened living system itself. For example, a pumpkin’s skin has antifungal proteins to prevent fungal growth without harming the pumpkin itself.

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Move in/on Liquids

Water is not only the most abundant liquid on earth, but it’s vital to life–so it’s no surprise that the majority of life has evolved to thrive on and under its surface. Moving efficiently in and on this dense and dynamic substance presents unique challenges and opportunities for living systems. As a result, they have evolved countless solutions to optimize drag, utilize surface tension, fine tune buoyancy, and take advantage of various types of currents and fluid dynamics. For example, sharks can slide through water by reducing drag due to their streamlined shape and specially shaped features on their skin.

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AIRCOAT is a marine coating that prevents biofouling and reduces friction by creating a layer of air along the hull.

Benefits

Reduced fuel consumption
Reduced energy use
Reduced emissions
Reduced biofouling

Applications

Maritime transportation
Maritime shipping

UN Sustainable Development Goals Addressed

Goal 11: Sustainable Cities & Communities
Goal 12: Responsible Production & Consumption

The Challenge

The shipping industry is one of the largest sources of greenhouse gas emissions due to the huge amount of fuel consumption from barges that transport containers across the ocean. When marine organisms attach to the bottom of the vessels it slows the ships down, requiring more fuel to travel the same distance. The emissions from this additional fuel consumption impact many elements of our daily lives, including increased air and water pollution.

Innovation Details

The Air Induced friction Reducing ship COATing (AIRCOAT) project aims to develop a passive air lubrication technology that utilizes the “Salvinia effect” to trap air underwater. The material is made up of micro and nanostructures with hydrophobic surfaces and hydrophilic tips that trap a layer of air. This material is then applied to a self-adhesive foil that can be attached to boat hulls, where it helps to protect the ship from biofouling and decreases the friction along the hull.

The AIRCOAT material mimics the Salvinia effect by creating a hydrophobic surface with hydrophilic tips that trap a layer of air.

The AIRCOAT material is then applied to a self-adhesive foil, known as the AIRCOAT foil.

Biological Model

The floating water fern, Salvinia, is a unique plant in that it retains pockets of air when fully submerged underwater. This capability, which provides the plant with buoyancy, is due to the surface structure of its leaves. The leaves are covered in tiny hairs, and each hair is coated in hydrophobic (water-repelling) wax crystals from its base almost to the tip. The very tip of each hair lacks the hydrophobic wax and is instead hydrophilic, which means it attracts water molecules. It is these hydrophilic tips that help retain air pockets when the plant is submerged. They enable the trapping of a thin layer of air between the leaf surface and the water that they attract, also known as the “Salvinia effect”.

See Related Strategy

close up photo of a green plant in water

Biological Strategy

Leaf Structure Retains Air Layer Underwater

Giant salvinia

The leaf structure of the Salvinia water fern retains a layer of air when submerged in water due to water-resistant hairs that possess water-attracting tips.

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