Hierarchical gecko-inspired nanohairs with a high aspect ratio induced by nanoyielding

We present a simple method for fabricating hierarchical polymeric nanohairs using a multi-branched anodic aluminum oxide (AAO) template prepared by two-step anodization and barrier layer thinning processes. Combined with nanohair yielding of a polymeric material during peeling-off from the hydrophobically modified AAO template, elongated hierarchical nanohairs with a high aspect ratio were fabricated without fiber collapse, which showed excellent adhesive and frictional properties compared to other structures such as single-level nanohairs and hierarchical nanohairs with a low aspect ratio. Furthermore, this surface showed remarkable superhydrophobic properties similar to those of natural gecko foot hairs.