Water-droplet adhesiveness was freely controlled on a single platform of superhydrophobic anodized aluminum oxide (AAO) within the range from highly adhesive to self-cleanable. Changing the structure from nanopore to nanopillar arrays at the surface caused a dramatic increase in the receding angle and a decrease in the hysteresis of water contact angles. The presence of dead-end nanopores but not through nanoholes was recognized as one of the main causes of the adhesiveness of superhydrophobic surfaces. The adhesiveness-controllable superhydrophobic AAO can be an excellent platform on which to elucidate the physical nature of the wetting phenomenon related to the nanostructure and has promising potential in technological applications.

, the bottom area of , the top area of , and the bottom area of .Controlling the wetting property of a surface to be superhydrophobic has been an attractive subject in science and technology.1-4 Self-cleanable superhydrophobic surfaces promise not only the self-removal of undesired contaminants from the surfaces of high-end products, but also a decrease in the surface energy of the mother molds for the easy departure of a replica pattern in template base lithography.Anodized aluminum oxide (AAO) is a well-defined nanoporous template to produce ordered pillar patterns 5-7 or rod-type nanostructures, [8][9][10][11][12][13][14] because the pore size, depth and ordering regime of the resulting pattern can be tuned in the nanometer scale.15-17 Fabrication of organized molecular assembly (selfassembled monolayer, SAM) on a micro-or nano-scale structured surface with a low free energy material is an effective approach for obtaining a hydrophobic or a superhydrophobic surface. One technical detail that should be considered in the coating of a SAM on nanoporous surface is the dehydration of nanopores. Because the AAOs are obtained from acidic aqueous solutions and the pore-depth to diameter aspect ratio strongly affects the hysteresis in the permeability and capillary pressure, 18 dehydration of the water-filled nanopores is crucial for fabricating a well-defined SAM in the pores. This paper suggests an effective process for fabricating a heptadecafluoro-1,1,2,2-tetrahydrodecyl-trichlorosilane (HDFS) monolayer to reduce the surface energy of porous AAO focusing on its superhydrophobicity and its use as a nanoimprinting template. An ultrapure aluminum plate (Goodfellow, UK) was laser cut into 2 × 5 cm 2 pieces. A well-ordered oxalic AAO (OAAO) mold was fabricated by two-step anodizing in an oxalic acid solution (0.3 M) at 40 V followed by post-etching for 25 min. The phosphoric AAO (PAAO) mold also was obtained with phosphoric acid (0.1 M) at 193 V. Dehydration of the AAOs was carried out in two different ways. One was 'simple drying' with a gentle stream of N2 gas (OAAO-sd and PAAO-sd), and the other was the more effective 'MeOH-exchange dehydration' (OAAO-md and PAAO-md) with soaking in methanol for more than 1 hour followed by drying in a vacuum desiccator. The plates were then soaked into a 1 mM solution of HSFS (Gelest Inc., Penn.) in n-hexane for 1 hour.The cross-section FE-SEM image of OAAO in Figure 1 (a) shows well-ordered straight nanometer-scale holes (several tens nanometer of the diameter) with a micrometer-scale depth a These authors contributed equally.(3.32 µm). The fabrication of a self-assembled HDFS monolayer on the surface with the two different dehydrations was investigated using wavelength dispersed spectroscopy (WDS) and contact angle (CA) measurements. The WDS of the OAAOs were obtained by JXA-8500F electron probe micro analyzer (EPMA, Jeol, Japan). The silicon peak, which is due to the HDFS molecular layer, was detected with discrete peaks at both the lower and upper regions of the grown oxide in...