Twenty-nine species of butterflies were collected for observation and determination of the wing surfaces using a Scanning Electron Microscope(SEM).Butterfly wing surface displays structural anisotropism in micro-,submicro- and nano-scales.The scales on butterfly wing surface arrange like overlapping roof tiles.There are submicrometric vertical gibbosities,horizontal links,and nano-protuberances on the scales.First-incline-then-drip method and first-drip-then-incline method were used to measure the Sliding Angle(SA)of droplet on butterfly wing surface by an optical Contact Angle(CA)measuring system. Relatively smaller sliding angles indicate that the butterfly wing surface has fine self-cleaning property.Significantly different SAs in various directions indicate the anisotropic self-cleaning property of butterfly wing surface.The SAs on the butterfly wing surface without scales are remarkably larger than those with scales,which proves the crucial role of scales in determining the self-cleaning property.Butterfly wing surface is a template for design and fabrication ofbiomimetic materials and self-cleaning substrates.This work may offer insights into how to design directional self-cleaning coatings and anisotropic wetting surface.
Gang Sun~(1,2), Yan Fang~(1,2), Qian Cong~1, Lu-quan Ren~11. Key Laboratory of Terrain-Machine Bionics Engineering (Ministry of Education, China), Jilin University,Changchun 130022, P. R. China2. School of Life Science, Changchun Normal University, Changchun 130032, P. R. China
The micromorphologies of surfaces of several typical plant leaves were investigated by scanning electron microscopy（SEM）. Different non-smooth surface characteristics were described and classified. The hydrophobicity and anti-adhesion of non-smooth leaf surfaces were quantitatively measured. Results show that the morphology of epidermal cells and the morphology and distribution density of epicuticular wax directly affect the hydrophobicity and anti-adhesion. The surface with uniformly distributed convex units shows the best anti-adhesion, and the surface with regularly arranged trellis units displays better anti-adhesion. In contrast, the surface with randomly distributed hair units performs relatively bad anti-adheslon. The hydrophobic models of papilla-ciliary and fold-setal non-smooth surfaces were set up to determine the impacts of geometric parameters on the hydrophobicity. This study may provide an insight into surface machine molding and apparent morphology design for biomimetics engineering.
Lu-quan Ren Shu-jie Wang Xi-mei Tian Zhi-wu Han Lin-na Yan Zhao-mei Qiu
Bionic alumina samples were fabricated on convex dome type aluminum alloy substrate using hard anodizing technique. The convex domes on the bionic sample were fabricated by compression molding under a compressive stress of 92.5 MPa. The water contact angles of the as-anodized bionic samples were measured using a contact angle meter （JC2000A） with the 3μL water drop at room temperature. The measurement of the wetting property showed that the water contact angle of the unmodi- fied as-anodized bionic alumina samples increases from 90° to 137° with the anodizing time. The increase in water contract angle with anodizing time arises from the gradual formation of hierarchical structure or composite structure. The structure is composed of the micro-scaled alumina columns and pores. The height of columns and the depth of pores depend on the ano- dizing time. The water contact angle increases significantly from 96° to 152° when the samples were modified with self-assembled monolayer of octadecanethiol （ODT）, showing a change in the wettability from hydrophobicity to su- per-hydrophobicity. This improvement in the wetting property chemical modification. is attributed to the decrease in the surface energy caused by the
