Bioinspired Fabrication of Bi/Tridirectionally Anisotropic Sliding Superhydrophobic PDMS Surfaces by Femtosecond Laser

Precisely arranged multiscale microstructures in living systems provide inspirations for the fabrication of artificial advanced materials and devices. Recently, uni-bioinspired surfaces with anisotropic wettability are built for various applications. Here, a kind of bi-bioinspired (rice leaf and butterfly wing) tridirectionally anisotropic sliding superhydrophobic surface for the first time is reported. First, a microgroove array structured polydimethylsiloxane surface is constructed by selective femtosecond laser ablation. The as-prepared surface shows bidirectional anisotropy which can be easily tuned by the width (L) and the depth of the microgrooves. A steps structure is further introduced into the microgrooves. Interestingly, tridirectionally anisotropic sliding superhydrophobicity that combined the rice-leaf-like and butterfly-wing-like anisotropy is achieved on such surface. The tridirectional anisotropy is demonstrated to result from the directional steps structures and the uneven distribution of rough structures. The bi/tridirectionally anisotropic sliding property will provide a fresh cognition of anisotropic wettability for researchers and have enormous potential applications in smart microfluidic systems.