Black Silicon Surface Destroys Wide Range of Bacteria

The biomimetic analogue Black Silicon (bSi) could present a new generation of mechanoresponsive, antibacterial nanomaterials, according to a new study.

Researchers at the Swinburne Institute of Technology (Swinburne, Melbourne, Australia), the Melbourne Center for Nanofabrication (Australia), and other institutions observed that the wings of the cicada Psaltoda claripennis could shred certain types of rod-shaped bacteria via clusters of nanoprotrusions that created a mechanical bactericidal effect independent of their chemical composition. They also identified other insects with similar spike-like surface architectures, such as the wings of Diplacodes bipunctata (the Wandering Percher dragonfly) that are even more deadly.


This prompted them to examine if the same properties existed in bSi, a synthetic nanomaterial that contains high aspect ratio nanoprotrusions on its surface produced through a simple reactive-ion etching (RIE) technique used in photovoltaic applications. They found that both natural structures and synthetic material exhibit estimated average killing rates of ~450,000 cells min⁻¹ cm⁻². Among the variety of bacteria, the surfaces were able to kill were deadly strains of Staphylococcus aureus. The study was published on November 26, 2013, in Nature Communications.

“Mechanoresponsive surfaces could play in countering microbial contamination, suggesting that novel antimicrobial nanomaterials may open the way for new applications in the field of mechano-microbiology,” concluded lead Prof. Elena Ivanova, PhD, of the Swinburne faculty of life and social sciences, and colleagues. “A new generation of antibacterial nanomaterials could be applied to the surfaces of medical implants, making them far safer.”

Black silicon is a semiconductor material, a surface modification of silicon with very low reflectivity and correspondingly high absorption of visible and infrared (IR) light. The modification was discovered in the 1980s as an unwanted side effect of RIE. The surface structure is made of single-crystal silicon needles with a height above 10 µm and diameter less than 1 µm. While smooth to the human touch, the surface ruthlessly destroys Gram-negative and Gram-positive bacteria, as well as bacterial spores.

Related Links:
Swinburne Institute of Technology
Melbourne Centre for Nanofabrication