Spiky surface, destructive to bacteria

Originally discovered by accident in the 1980s, black silicon is silicon with a surface that has been modified to feature nanoscale spike structures which give the material very low reflectivity. Researchers have now found that these spikes can also destroy a wide range of bacteria, potentially paving the way for a new generation of antibacterial surfaces…

Surface structures similar to black silicon can be found in nature. Earlier this year, researchers at the Swinburne Institute of Technology in Australia led by Professor Elena Ivanova and Professor Russell Crawford found that the wings of the cicada Psaltoda claripennis could shred certain types of rod-shaped bacteria.

This prompted them to seek out other insects with similar spike-like surface architectures. They found that the wings of the Diplacodes bipunctata or Wandering Percher dragonfly were even more deadly, killing both rod-shaped and spherical bacteria.

“This structure generates a mechanical bacteria killing effect which is unrelated to the chemical composition of the surface,” says Professor Russell Crawford, who is Dean of the Faculty of Life and Social Sciences at Swinburne.

The team then set out to mimic the surface structure of the Wandering Percher dragonfly wing in an effort to create a surface with similar bacteria-killing properties. They then compared the bacteria-killing capacity of their black silicon creation to the dragonfly wing.

“Both surfaces were found to be highly effective against a range of bacteria, as well as endospores,” says Professor Crawford. “They exhibited estimated average bacteria killing rates of up to 450,000 cells per minute of exposure, for every square centimeter of available surface.”

Among the variety of bacteria the surfaces were able to kill were the deadly strains of the Staphylococcus aureus or golden staph bacterium.

“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,” he adds.

Some of the results flowing from nanomaterials research is incredible in the range of unpredictable findings. Especially in a case like this one where the effect is directly caused by physical structure alone. Wow.