Fabrication of Super-hydrophobic Surfaces and Studies of Water Flow in Super-hydrophobic Micro-tubes

Abstract

Abstract Hierarchical alveolate structures of micro-nano scale were prepared on stainless steel substrates with chemical etching. Fine papillae stand on protuberances are found. After fluorination treatments, the surfaces exhibit super-hydrophobic properties, with water contact angles of 163°. Stainless-steel micro-tubes with super-hydrophilic and super-hydrophobic surface were fabricated with chemical etching and chemical etching-fluorination treatment respectively. The effect of surface wettability on the fluid flow in micro-tubes was investigated with water as the working fluid. The experimental setup was designed in such a way that the investigation of the pressure drop and friction factor was possible. It is found that friction factor in super-hydrophilic micro-tube is in good agreement with Hagen-Poiseuille theory at low Reynolds number (Re<600), while higher than classical values at higher Reynolds number. The pressure drop of water flowing in super-hydrophobic micro-tube decreases compared with that in super-hydrophilic micro-tube, with the maximal decrease of 39%, which indicates the prospective utilization in process industry.