Application of projection lithography using a gradient-index lens array and wet etching to texturing for control of the hydrophobic properties of stainless-steel plates

Abstract

The effectiveness of line-and-space (L&S) textures grooved onto stainless-steel SUS 304 plates for improving hydrophobic properties was investigated. The textures were grooved using a scan-projection exposure system with a gradient-index lens array as a projection lens and wet chemical etching in ferric chloride aqueous solution. The lithography system was applied because it was developed for printing rough patterns of larger than 15 μm in a large exposure field of 50 mm square. On the other hand, it was expected that textured protrusions with considerably sharper peaks might be formed by the undercut phenomenon during wet etching. When the contact angles of 2 μl pure-water droplets which had been dropped down onto 20 μm L&S textures were measured, it was found that contact angles measured by observing a droplet from the L&S direction were larger than those measured from the direction perpendicular to the L&S, and contact angles were changeable by grooving textures of different sizes.