Figure 4. Bactericidal efficiency of black silicon and dragonfly wings.

The bactericidal efficiency of both the bSi and D. bipunctata wing surfaces over the first 3 h of incubation was calculated as the number of cells killed per square centimetre of projected sample surface area, per minute of incubation time. The number of cells killed was determined by subtracting the number of surviving cells from the number of cells remaining in controls at the corresponding time interval. The uncertainty values represent the natural variability associated with biological systems, and were calculated based on standard deviations in colony forming units. Error bars are based on s.d. values.