Figure 2.

Characterization of nanostructured surface topography used in these experiments. Top row consists of helium ion micrographs at 68 000× magnification; middle row are the corresponding atomic force micrographs providing better topographical information; bottom row, cartoon representation of an edge-on view of nanoscale topography and contact angle information. (a,a′,a″) Au-coated glass cover slip/control, relatively featureless surface aside from occasional debris. (b,b′,b″) Au-coated wing of periodical cicada Magicicada septendecim displaying approximately hemispherical features with a mean diameter of 167 nm. (c,c′,c″) Au-coated wing of annual cicada Tibicen tibicen displaying spherically capped conical protrusions with a mean length of 183 nm and mean cap diameter of 57 nm. (d,d′,d″) Au-coated wing of common sanddragon dragonfly, Progomphus obscure, displaying high aspect ratio spherically capped cylindrical protrusions which appear to be bundles of three to five smaller protrusions with a mean length of 241 nm and a mean bundle diameter of about 50 nm at the cap. The bottom row shows the contact angle measurements of each NSS. Refer to table 1 for more details on geometry of these surfaces. (Online version in colour.)