Research carried out by Key Laboratory for Terrain Machine Bionics Engineering of Ministry of Education, Jilin University in Changchun, China, has shown that the co-coupling effect of scale biomaterial, micron-class shape and nanometer-class structure of vertical gibbosities of scale can induce surface hydrophobicity and self-cleaning function of the moth wing. The study is reported in Volume 54, Issue 4 (February, 2009) of Chinese Science Bulletin because of its significant research value.
The hydrophobicity, self-cleaning, anti-oxidation and pollution guarding characteristics on object surface have been found to have very wide applications to industrial, agricultural, domestic and military fields. Until now, the relationship between wetting characteristic on moth surface and scales arrangement pattern, ultrastructure and material has not been defined.
In this work, the surface shape, structure, biomaterial and wettability of moth wings (10 NOCTUIDAE species) from the northeast region of China were qualitatively and quantitatively studied. The observation shows that there are scales arranged like overlapping tiles on the surfaces of the moth wings. The shapes of the scales are different between species. They overlap horizontally and there is particular space vertically in the direction of the wing veins. The surface of the scale is structured by micron-class grooves and nanometer-class vertical gibbosities. The biomaterial components of the moth wing scale are mostly made up of protein, lipids and chitin. The observation also shows that the contact angle for wings with scales is in the range from 144.8° to 152.9°, while that for those without scales is from 90.0° to 115.9°. It indicates that the surfaces of the wings with scales are more hydrophobic. In addition, the equation of wettability on the NOCTUIDAE moth wing surface is established and the hydrophobic mechanism is analyzed.
This study presents that the hydrophobicity of the moth wings is induced by the multivariate coupling of the shapes, structures and biomaterials of the scales.The biomaterials are hydrophobic. And the hierarchical rough structure on moth wing surface enhances surface hydrophobicity. So the moth wing surface can not be adhered to by rainwater, dew and dust so that it keeps the flying balance, improves the flying speed and ensures flying safety. This work provides theoretical guidance to the design of perfect artificial superhydrophobic and self-cleaning materials.
The authors are affiliated to Key Laboratory for Terrain Machine Bionics Engineering of Ministry of Education. This laboratory is conducting research mainly in four respects: bionic walking of terrain machinery on soft terrain, biomimetic theory and technology on anti-adhesion and resistance reduction of terrain-machine, design on the machines to produce and process living creature and the technique of bionics, biomimetic tribology and biomimetic materials.
Funding is from the Key Research Project under the National Natural Science Foundation of China (Grant No. 50635030), Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20040183048)
Reference: Yuan Z Q, Chen H, Tang J X, etc. Facile method to fabricate stable superhydrophobic polystyrenesurface by adding ethanol. Surf Coat Tech, 2007(201): 7138―7142
Guo Z G, Liu W M. Biomimic from the superhydrophobic plant leaves in nature: Binary structure and unitary structure. Plant Sci, 2007(172): 1103―1112
Wang J D,Yu Y,Chen D R。Research progress on the ultra hydrophobic surface topography effect. Chinese Sci Bull, 2006, 51(19): 2297―2300
Blossey R. Self-cleaning surfaces-virtual realities. Nat Mater, 2003(2): 301―306
Ma M L, Randal M. Hill. Superhydrophobic surfaces. Curr Opin Colloid Interface Sci, 2006(11): 193v202
Bo H, Junghoon Lee, Neelesh A. Patankar. Contact angle hysteresis on rough hydrophobic surfaces.Colloid and Surface A: Physicochem. Eng. Aspects, 2004(248): 101―104
Abraham Marmur. The Lotus Effect: Superhydrophobicity and Metastability. Langmuir, 2004(20): 3517―3519
Barthlott W, Neinhuis C. Purity of the sacred lotus, or escape from contamination in biological surfaces. Planta, 1997, 202(1): 1―8
Neinhuis C, Barthlott W. Characterization and distribution of water-repellent, self-cleaning plant surfaces. Annals Botany, 1997, 79(6): 667―677
Fang Y, Sun G, Wang T Q, Cong Q. Hydrophobicity mechanism of non-smooth pattern on surface of butterfly wing. Chinese Sci Bull, 2007, 52(5): 711―716
Steve Herman. The wing of a butterfly. Global Cosm Ind, 2002, 170(8): 32―35
Cassie A, Baxter S. Wettability of porous surfaces. Trans Faraday Soc, 1944(40): 546―551
Michael Nosonovsky, Bharat Bhushan. Hierarchical roughness makes superhydrophobic states stable. Microelectron Eng, 2007(84): 382―386
Adamson A.W., Cast A.P..Physics chemistry of surfaces. New York: John Wiley ＆ Sons, 1997
Journal
Chinese Science Bulletin