Black silicon spacing effect on bactericidal efficacy against gram-positive bacteria

The morphology of regular and uniform arrays of black silicon structures was evaluated for bactericidal efficacy against gram-positive, non-motile Staphylococcus epidermidis (S. epidermidis). In this study, uniform and regular arrays of black silicon structures were fabricated using nanosphere lithography and deep reactive ion etching. The effects of nanomorphology on bacterial killing were systematically evaluated using silicon nanostructures with pitches ranging from 300 to 1400 nm pitch on spherical cocci approximately 500 to 1000 nm in diameter. Our results show that nanostructure morphology factors such as height and roughness do not directly determine bactericidal efficacy. Instead, the spacing between nanostructures plays a crucial role in determining how bacteria are stretched and lysed. Nanostructures with smaller pitches are more effective at killing bacteria, and an 82 +/- 3% enhancement in bactericidal efficacy was observed for 300 nm pitch nanoneedles surface compared to the flat control substrates.