Anisotropic property of the multiple-dimensional rough surface on moth wing

The micro-morphology, superhydrophobicity, self-cleaning property and chemical composition of the moth wing surface were investigated by a Scanning Electron Microscope (SEM), a contact angle meter and a Fourier transform infrared spectrometer (FT-IR). The wetting mechanism of the moth wing was discussed from the perspective of biological coupling. The moth wing displays multiple-dimensional structural anisotropism. The micrometric scales constitute the primary structure, the submicrometric vertical ribs and horizontal bridges on the scales constitute the secondary structure, and the nano stripes on the vertical ribs and horizontal bridges constitute the tertiary structure. The moth wing surface is of superhydrophobicity (contact angle 150.5 similar to 158.4 degrees) and low adhesion (sliding angle 1 similar to 3 degrees). In addition, the water droplet exhibits anisotropic sliding behavior on the wing surface. The scale plays a crucial role in determining the self-cleaning property of the moth wing. The coupling effect of material element and structural element contributes to the special wettability of the wing surface. The moth wing can be potentially used as a template for biomimetic design of functional surface with complex wettability. This work may offer insights into the preparation of smart interfacial material and directional self-cleaning coatings.