From a whale shark keeping unwanted freeloaders off its skin to water droplets rolling off a duck’s feathers, nature has many ingenious ways of keeping surfaces clean.
The science of biomimicry, or biomimetics, seeks to harness nature’s cleverest capabilities which have taken aeons to evolve.
Scientists at AkzoNobel, a global paints and coatings company, are using principles derived from nature to develop coatings that protect surfaces such as the hulls of cargo ships. And other heavy industries such as rail are experimenting with biomimicry too. The designers of Western Japan Railway’s bullet trains looked to the kingfisher for solutions on how the train could adjust its speed more efficiently when approaching a tunnel, modelling its front on the diving bird’s beak. At motion and control technologies company Parker Hannifin, scientists modelled a new hose on snake skin to make it more durable than earlier models.
“Evolution has given us a lot of potential solutions that we can adapt,” says Gareth Crapper, research director, performance coatings, at AkzoNobel. “In terms of resisting attack by the environment, nature faces that problem all the time. Imagine the first fish crawling onto the shore, and the UV radiation challenges they faced.”
Intelligent biocides
Fouling — the buildup of dirt, bacteria, weed and shellfish — adds weight and resistance to vessels. The right anti-fouling coating can save fuel, sometimes up to 40%, and consequently reduce carbon emissions.
Among AkzoNobel’s innovations is a coating inspired by the venus flytrap, a carnivorous plant which releases a sticky substance and closes its “jaws” once an insect lands on its petals.
Current coatings typically contain biocides — substances that are toxic to particular pests — which are most effective soon after the coating is applied. New so-called intelligent biocides are designed to only release their chemicals when the surface is damaged, or a harmful organism is attached.
“You encapsulate materials inside microspheres in the paint, so they sit there doing nothing until the moment the paint is damaged,” Crapper says.
Efficient fouling prevention also helps keep maintenance low and adds to the longevity of shipping fleets, adds Crapper.
While biocides can be harmful to the marine environment, coatings that contain them are commonly perceived as performing better than non-biocidal solutions, especially when the ship is inactive — which is when much of the fouling builds up.
However, biocides are highly regulated and new products can cost between €6-9m to bring to market. Crapper says he expects to see regulation on biocides tightening still further, making it more practical, cost-effective and environmentally friendly for ship owners to find a new solution.
Non-biocidal solutions
AkzoNobel, which has marketed the leading non-biocidal brand, Intersleek for 21 years, is now experimenting with biomimetic solutions as well. These mimic how sharks and ducks stop organisms from attaching themselves to their skin or feathers. The coatings repel organisms without releasing chemicals and make them easier to shake off.
“We welcome the legislative pressure, and we are trying to be ahead of the game,” says Crapper.
Their sharklet technology, also known as riblets, is currently in trials with clients. Inspired by the texture of a shark’s ribbed skin, a natural non-stick surface, the coatings can also be used for aerodynamic drag reduction, and are being tested by two of the world’s largest commercial aircraft manufacturers.
Research into the ways penguins move in cold waters has shown that they create air pockets of bubbles when swimming through icy waters at speed — “air lubrication”. Similarly, bubbles piped beneath a vessel function like a cushion. This “penguin cushion” method can help ships reduce drag and save fuel.
Like water off a duck’s back
AkzoNobel’s work with superhydrophobic coatings involves mimicking how water falls off a duck’s back, or rolls off the leaves of a lotus flower.
“Thanks to a combination of factors, the water does not wet the surface, or rolls off very easily,” explains Crapper. Applications for these coatings include preventing water from settling on the blades at wind farms, keeping them productive in all weathers.
“If the wind turbine ices up, you have to switch it off for the winter, because if you keep running you run the potential of flinging kilogram sized blocks of ice long distances from the blade,” he adds.
A leap into the future
AkzoNobel’s team of biologists, physicists, and materials scientists, who collaborate with institutions such as the Natural History Museum, are now taking a leap into the future, combining biomimicry with futuristic inspiration.
It’s still early days, but the result could be anything from microelectronic sensors detecting corrosion to integrating LEDs into coatings and using microelectronics to prevent fouling.
Muses Crapper, “We ask ourselves, what would a coating look like in Star Trek?”
