Design of hydrophobic surfaces for liquid droplet control

Technologies related to hydrophobic coatings have been applied to various industrial items for droplet formation and removal from solid surfaces. However, for such surfaces, excellent water-shedding properties and droplet control in a desired direction are not easily attainable merely by reducing their surface energies. Success requires the design and control of a nanolevel surface structure with appropriate chemical composition. Various hydrophobic surfaces have been developed to date, and their static hydrophobicity has been investigated carefully. Moreover, studies of dynamic hydrophobicity of droplets have increased recently because of the rapid advance and availability of high-speed cameras, facilitating direct evaluation of droplet motion. This paper presents a review of recent studies investigating the design of hydrophobic surfaces for liquid droplet control, specifically focussing on recent studies of dynamic hydrophobicity.