Effect of Physical Properties on Micro-Structured Surfaces for Hydrophilic Control

The wettability of solid surfaces can be caused artificially by chemical or structural effects. Property control by the former chemical effect has been applied to various products and has been put into practical use. However, it is not suitable for permanent use due to the possibility of chemical property changes over time. In other words, it is necessary to repeat the treatment again, and cost is one of the issues. For this reason, the attention is being paid to the structural effects of this wettability, which are manifested by micro-structured surfaces. However, the appropriate microstructure to achieve the desired wettability is not well understood. Therefore, many studies have been carried out worldwide to control wettability, i.e. hydrophobicity and hydrophilicity, by using microstructures. This study focused our investigations on the hydrophilicity among these properties. In this study, regular micro-structured surfaces with a regular arrangement of cylinders on a solid surface were fabricated using photolithography and reactive ion etching (RIE). The vertical tilt and height of the cylinders were adjusted by controlling the RIE processing conditions using single crystal silicon and glass as working materials. The effects of these changes on hydrophilicity and droplet shape were investigated. As a specific implementation method, patterning was carried out by photolithography using SU8 resist on single crystal silicon or glass substrates, and using this as a mask, a mixture of CF4, SF6 and O2 gas were used in the etching process. The similarities and differences in fabrication methods and properties such as hydrophilicity of micro-textures on single crystal silicon and glass substrates were investigated.

Keywords: Wettability, Hydrophilicity, Microstructure, Si substrate, Glass substrates.

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