The Nepenthes pitcher plant (left) and its nanowrinkled 'mouth' (centre) inspired the engineered polymer nanomaterial (right). Image: Sydney Nano.
The Nepenthes pitcher plant (left) and its nanowrinkled 'mouth' (centre) inspired the engineered polymer nanomaterial (right). Image: Sydney Nano.

A team of chemistry researchers from the University of Sydney Nano Institute in Australia has developed nanostructured surface coatings that possess anti-fouling properties, without using any toxic components.

Biofouling – the build-up of damaging biological material – is a huge economic issue, costing the aquaculture and shipping industries billions of dollars a 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 around Aus$320 million a year. The banning of the toxic anti-fouling agent tributyltin has led to a pressing need for new non-toxic methods to stop marine biofouling.

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

The team tested the new nanostructured coatings by attaching them to shark netting in Sydney's Watson Bay, showing that the nanomaterials were efficient at resisting biofouling in a marine environment. The researchers report their findings in a paper in ACS Applied Materials & Interfaces.

The new coating employs polymer 'nanowrinkles' inspired by the carnivorous Nepenthes pitcher plant, which traps a layer of water on tiny structures around the rim of its opening. This layer is slippery, causing insects to aquaplane on the surface before they slip into the pitcher to be digested.

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

In the lab, the slippery surfaces resisted almost all fouling from a common species of marine bacteria, while control Teflon samples without the lubricating layer became 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, with the help of marine biologist Ross Coleman. Test surfaces were attached to swimming nets at Watsons Bay baths in Sydney Harbour for a period of seven weeks. In this 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 interdisciplinary University of Sydney team included biofouling expert Truis Smith-Palmer of St Francis Xavier University in Nova Scotia, Canada, who was on sabbatical visit to the Neto group for a year.

This story is adapted from material from the University of Sydney, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.