Improvement of Hydrophobic Property of Stainless-Steel Plates by Forming Lens-Like Protrusions Similar to Oxalis Leaf Surfaces

Abstract

Leaves of an obscure plant “oxalis deppei” are so hydrophobic that showered water droplets are almost completely repelled and hardly remained on their surfaces. For this reason, surface configurations were investigated. On the live leaves, there formed protrusions somewhat similar to those observed on lotus leaves which are well known as super hydrophobic leaves. However, in winter, it was found that even dead leaves were hydrophobic also. Because leaf tissues were shriveled and dried half, heights of protrusions with sizes of 20-50 μm were low, and undulations of surfaces were gentle and smooth, and pitches of undulations were as large as 30-70 μm. It was thought that such gentle lens-like protrusions would be probably formed on versatile stainless-steel plates using lithography and wet chemical etching. For this reason, arrays of protrusions with a size of 20 μm, a pitch of 35 μm, and heights of 6-7 μm were formed, and change of hydrophobic properties were investigated. As a result, the hydrophobic properties were effectively improved by forming even such gentle and smooth protrusions. It was also clarified that contact angles were improved almost in proportion to etched depths.

Printing of Random Needle-like Resist Patterns Utilizing Laser Speckle Lithography

“…Some insects and plants have special functionality caused by minute surface structures on their body parts [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. For example, surfaces of lotus leaves and rose petals are water repellent [15][16][17][18][19][20].…”

Miniaturization of Scattered Random Patterns Formed by Lens·less Speckle Lithography

“…Owing to the research efforts, water repellency of plant leaves in nature [1][2][3][4][5][6][7], antireflection of moth eyes [8][9][10][11], and antibacterial properties of cicada wings are known [12][13][14], for example. It is believed that these characteristic surface functions can be reproduced by artificially forming similar microstructures on the surfaces of industrial materials [15][16][17][18][19].…”

Research on a New Lithography Method Utilizing Laser Speckles for Printing Random Patterns

“…Lotus leaves and rose petals have minute surface structures barely observable without using a microscope, and it causes their hydrophobic properties [1][2][3][4][5][6][7]. Similar hydrophobic performances have been discovered in various plants and insects though modified surface structures and the performances are different [8][9][10][11][12][13][14][15][16][17].…”