title: Theoretical Explanation of the Lotus Effect: Superhydrophobic Property Changes by Removal of Nanostructures from the Surface of a Lotus Leaf.
abstract: Theoretical study is presented on the wetting behaviors of water droplets over a lotus leaf. Experimental results are interpreted to clarify the trade-offs among the potential energy change, the local pinning energy, and the adhesion energy. The theoretical parameters, calculated from the experimental results, are used to qualitatively explain the relations among surface fractal dimension, surface morphology, and dynamic wetting behaviors. The surface of a lotus leaf, which shows the superhydrophobic lotus effect, was dipped in ethanol to remove the plant waxes. As a result, the lotus effect is lost. The contact angle of a water drop decreased dramatically from 161° of the original surface to 122°. The water droplet was pinned on the surface. From the fractal analysis, the fractal region of the original surface was divided into two regions: a smaller-sized roughness region of 0.3-1.7 μm with D of 1.48 and a region of 1.7-19 μm with D of 1.36. By dipping the leaf in ethanol, the former fractal region, characterized by wax tubes, was lost, and only the latter large fractal region remained. The lotus effect is attributed to a surface structure that is covered with needle-shaped wax tubes, and the remaining surface allows invasion of the water droplet and enlarges the interaction with water.
authors.affiliation: †Department of Materials Chemistry, Faculty of Science and Technology, Ryukoku University, Seta, Otsu 520-2194, Japan.
authors.forename: Minehide
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: ‡Mitsuboshi Belting Ltd., 4-1-21 Hamazoe-dori, Nagata-ku, Kobe 653-0024, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Nishikawa
authors.affiliation: §Research Institute for Electronic Science, Hokkaido University, N21, W10 Kita-ku, Sapporo 001-0021, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mayama
authors.affiliation: ∥Department of Biochemical Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16, Jonan, Yonezawa, Yamagata 992-8510, Japan.
authors.forename: Yoshimune
authors.initials: Y
authors.lastname: Nonomura
authors.affiliation: ⊥RIKEN Research Cluster for Innovation, Nakamura Laboratory, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.|#School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yokojima
authors.affiliation: ⊥RIKEN Research Cluster for Innovation, Nakamura Laboratory, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: †Department of Materials Chemistry, Faculty of Science and Technology, Ryukoku University, Seta, Otsu 520-2194, Japan.
authors.forename: Kingo
authors.initials: K
authors.lastname: Uchida
mesh_terms: D000268:Adhesiveness; D000431:Ethanol / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D000070116:Lotus / Q000737:chemistry*; D008958:Models, Molecular; D049329:Nanostructures / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014885:Waxes / Q000737:chemistry
chemical_list: D014885:Waxes; D014867:Water; D000431:Ethanol