Black silicon could become chemical-free germ killer

23rd of December 2013
Black silicon could become chemical-free germ killer

A substance that kills bacteria by ripping open their cell walls may be used to destroy germs in hygiene-critical environments such as hospitals.

The surface of black silicon, discovered by accident in the 1990s, is made up of a forest of tiny spikes or 'nanopillars'. Last year a team of scientists in Melbourne, Australia, were stunned to find that the wings of a cicada had a similar structure and that its regularly-spaced nanopillars were potent killers that sliced bacteria to shreds when they settled on the surface.

The scientists took the discovery further by examining the forewings of a red-bodied Australian dragonfly which were also found to be made up of bactericidal spikes. The team then looked at black silicon to see whether its own "nanopillars" had a similar bactericidal effect.

Both the black silicon and the dragonfly's wings were found to be able to destroy spores as well as Gram-negative and Gram-positive bacteria. The three bugs targeted were P. aeruginosa, Staphylococcus aureus and Bacillus subtilis, a wide-ranging soil germ related to anthrax. The killing rate was found to be 450,000 bacterial cells per square centimetre per minute over the first three hours of exposure.

The scientists are now looking at the possibilities of using black silicon as a bactericide in hygiene-critical environments such as hospitals and food preparation areas. And if the cost of producing it is an obstacle, there are options for making other nano-scale germ-killing surfaces, say the scientists.

"Synthetic antibacterial nano-materials that exhibit a similar effectiveness can be readily fabricated over large areas," they write.



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