Figure 1. Characterization of black silicon and D. bipunctata wings.

Scanning electron micrographs of the upper surface of (a) bSi and (b) dragonfly forewings at × 35,000 magnification demonstrate the surface patterns of the two samples. Scale bars, 200 nm. Micrographs tilted at an angle of 53° (inset) show sharper nanopillars of black silicon distinct from one another and approximately twice the height of those of the dragonfly wing. Optical profilometry shows the nanoprotrusions of (c) bSi and (d) dragonfly forewings. Scale bars, 50 μm; inset, 2 μm. Three-dimensional reconstructions based on a displacement map technique further highlight the differences and similarities of (e) bSi and (f) dragonfly forewings.