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Dragonfly wing model for antibacterial material

25 Feb, 2014

Australian scientists have developed a novel synthetic antibacterial coating inspired by dragonfly and cicada wings. The black silicon surface has nanoscale spikes or ‘nanopillars’, which literally stab and kill bacteria that try to settle on the surface – all without the need for antibacterial sprays, heat or ultraviolet radiation.

Wings have an unusual physical structure

Early in 2013, a team of researchers led by Swinburne University microbiologist Professor Elena Ivanova and Dean of the Faculty of Life and Social Sciences Professor Russell Crawford discovered that the wing of the cicada (Psaltoda claripennis) had an unusual physical structure that can shred certain types of rod-shaped bacteria.

“Based on this discovery, we investigated other insects that may possess similar surface architectures that might kill more bacteria, in particular the deadly strains of the Staphylococcus aureus or golden staph bacterium,” Professor Ivanova said in a press release from Swinburne.

Spike-like nanostructures pop and kill bacteria

Using scanning electron microscopy, they found that the wandering percher dragonfly (Diplacodes bipunctata) had a wing surface with spike-like nanostructures, some 240 nanometres tall, that can pop and kill both rod-shaped and spherical bacteria. The team then set about seeing if they could recreate the effect synthetically.

Working with Swinburne Professor of Nanophotonics Saulius Juodkazis, the team found that, by etching black silicon, a cheap material used in solar panels and light sensors, they could create long narrow nanoprotrusions on its surface that mimicked the surface structure of a dragonfly wing. When comparing the etched black silicon with the dragonfly wing surface, it was found to be just as effective at killing bacteria. The researchers stressed that this type of antibacterial surface doesn’t need to be black silicon – any material that could be similarly etched should have a similar result.

“This structure generates a mechanical bacteria killing effect which is unrelated to the chemical composition of the surface,” says Professor Crawford.

“Both surfaces [dragonfly wing and black silicon] were found to be highly effective against a range of bacteria, as well as endospores. They exhibited estimated average bacteria killing rates of up to 450,000 cells per minute of exposure, for every square centimetre of available surface.”

Potential uses in medical and food industries

“This represents an exciting prospect for the development of a new generation of antibacterial nanomaterials that could be applied to the surfaces of medical implants, making them far safer.”

There are a myriad of potential uses for the coating, including antibacterial surfaces for hospitals, medical equipment, food processing equipment and kitchens.

The research team also included researchers from the Melbourne Centre for Nanofabrication, the University of Melbourne, the Universitat Rovira i Virgili in Spain and James Cook University in Queensland.

The research was published online on 26 November 2013 in Nature Communications.

References

Ivanova, E. P. et al. (2013). Bactericidal activity of black silicon. Nature Communications 4, Article number: 2838 doi:10.1038/ncomms3838. Published online 26 November 2013. Retrieved 28 January 2014 from www.nature.com/ncomms/2013/131126/ncomms3838/full/ncomms3838.html

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