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Nanowrinkled Coatings Reduce Marine Biofouling

Chemists from the University of Sydney have developed nano­structured surface coatings that have anti-fouling properties without using any toxic components.

The build-up of biological material costs the aquaculture and shipping industries billions of dollars per year in maintenance and extra fuel usage. It is estimated that the increased drag on ship hulls due to biofouling costs the shipping industry in Australia $320 million per year.

Since the toxic anti-fouling agent tributyltin was banned, the need for new non-toxic methods to stop marine biofouling has been pressing.

“We are keen to understand how these surfaces work and also push the boundaries of their application, especially for energy efficiency. Slippery coatings are expected to be drag-reducing, which means that objects such as ships could move through water with much less energy required,” said team leader A/Prof Chiara Neto.

The new coating creates “nanowrinkles” inspired by the carnivorous Nepenthes pitcher plant, which traps a layer of water on the tiny structures around the rim of its opening. This creates a slippery layer that causes insects to aquaplane along the surface before they slip into the pitcher and are digested.

Biofouling can occur on any surface that is wet for a long period of time, such as aquaculture nets, marine sensors and ship hulls. The slippery surface developed by Neto’s group stops the initial adhesion of bacteria, inhibiting the formation of a biofilm from which larger marine organisms can grow.

In Neto’s lab, the slippery surfaces resisted almost all fouling from a common species of marine bacteria. In contrast, control Teflon samples without a lubricating layer were completely fouled.

Not satisfied with testing the surfaces under highly controlled lab conditions with only one type of bacteria, the team also tested the surfaces in the ocean by attaching them to swimming nets at Watsons Bay baths in Sydney Harbour for a period of 7 weeks. Despite the much harsher marine environment, the slippery surfaces were still very efficient at resisting fouling.

The antifouling coatings are mouldable and transparent, making their application ideal for underwater cameras and sensors.

The research has been published in ACS Applied Materials & Interfaces.