Preparation Of (Super)-hydrophobic Materials By Imitating The Microstructure Of Canna Leaf

Recently, the super-hydrophobicity of solid surface has been an important research subject because of its promising application prospect. There are various kinds of methods to prepare super-hydrophobic materials, and template method is one of the easiest ways to realize the industrialized production. The earliest studies on super-hydrophobic materials are on cuticles of animals and plants. In order to copy these rough structures on nature, super-hydrophobic surfaces(coded as SHS) on plants or animals have been used as templates to prepare SHS on polymeric substrates.Generally, the polymeric substrates are of low surface energy; consequently,fluorochemicals, which are generally used in other SHS preparation methods to lower surface energy, are not required. These two factors, i.e., the rough structures copied from nature and the inherent low surface energy, play important roles in SHS preparation.In this thesis, the surface wettability of canna leaf was systematically studied and used as template to fabricate SHS. The morphology, chemical composition, and surface wettability of canna leaf was investigated by optical microscope / scanning electron microscope, attenuated total reflectance infrared spectroscope, and contact angle meter,respectively. Results showed that the surface of canna leaf was densely covered with micro-scale regular arrayed convex quadrangles with short edge size of 30 ?m~50 ?m and long edge size of 60 ?m~ 100 ?m. Both the surface of micro-structures and the intervals of micro-structures are covered with many nano-structures like little crumbs or sheets in average size of ~500 nm. So, it can be demonstrated that the canna leaf is multi-scale structured with micro-structures and nano-structures. The outermost surface of canna leaf is covered by hydrophobic wax, the main component of which is aliphatic compound. These two factors, i.e., the multi-scale surface structures and the low surface energy by wax, lead to super-hydrophobicity. The water contact angle(WCA) with a droplet of 5 ?l on the canna leaf is 160.3°±0.6°, sliding angle(SA) 6°±2°.Canna leaf was then used as template to prepare SHS on polymeric substrate by using a double replica method. Results showed that the micro-structures of canna leaf were successfully transferred into the artificial materials. PDMS/PVC(the first moulding material is PDMS and the second moulding material is PVC, simple as PDMS/PVC) duplicated the micro-structures most successfully. For PVA/PS andPDMS/LDPE, similar multi-scale structures were found(i.e., nano-structures with typical size of hundreds of nanometers in micro-structures), however, some nano-structures had been stretched. The WCA and SA of 5 ?l droplet on the surface of PVA/PS is 156.8°±1.8°and 47°±4°, respectively; for PDMS/LDPE, 141.5°±3.6° and 90°,respectively; for PDMS/PVC, 160.9°±1.0° and 7°±3°, respectively.