AVS 51st International Symposium
    Nanometer-scale Science and Technology Tuesday Sessions
       Session NS-TuP

Paper NS-TuP28
Behavior of Water Microdroplets on Nano-textured Surfaces Fabricated by a Focused Ion Beam Technique

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: M. Kouno, Nagoya University, Japan
Authors: M. Kouno, Nagoya University, Japan
Y. Wu, Nagoya University, Japan
N. Saito, Nagoya University, Japan
M. Koga, Nagoya University, Japan
Y. Inoue, Nagoya University, Japan
O. Takai, Nagoya University, Japan
Correspondent: Click to Email
Water repellency emerged on hydrophobic surfaces has attracted much attention due to fundamental and scientific interests. Surface nano-texture is a key factor for water repellency. Water repellency is generally evaluated by water contact angle. The water contact is usually evaluated in macrometer-scale. Environmental scanning electron microscopy (E-SEM) has the potential of the evaluation in micro-meter scale. In this study, we investigated the correlation between the surface structure and the water repellency based on the observation of water droplets in micro-scale using E-SEM. We prepared two types of samples with different nano-textured surface fabricated by a focused ion beam (FIB) technique. One was consisted of a fine array of concave structures with the center distances being 1 µm on Si(100) substrate. The other was composed of a similar array of convex structures. Their diameters were varied from 150 to 800 nm. All the sample surfaces were modified with the formation of a self-assembled monolayer from heptadecafuluoro-1,1,2,2-tetrahydro-decyl-1-trimethoxysilane [a type of fuloroalkylsilane, FAS, F@sub 3@C(CF@sub 2@)@sub 7@(CH@sub 2@)@sub 2@Si(OCH@sub 3@)@sub 3@] through chemical vapor deposition. These samples were observed by ESEM (Nikon, ESEM-2700). Water droplets were in situ formed on each sample surface by cooling the sample down to ca. 2.5 @super o@C, which is lower than the dew point under the condition of observation chamber. E-SEM images of the water droplets revealed that the water repellency of the sample depends on the shape and the array pattern on the surface in nanometer-scale.