Abstract
In this work, micromilling and laser-etching microfabrication techniques are trialed for mimicking the super water repellence of the lotus leaf and the directional water droplet control of the Namib desert beetle. To further alter the surface wetting properties, subsequent ion-beam surface modification techniques are used. Ion-beam postprocessing is used to create an additional nanoroughness on a microstructure as well as a controllable Gibbs surface free energy change of the substrate material. The in-plane spreading for control (smooth) surfaces are compared to the micropatterned surfaces and combined micropatterned and ion-beam processed surfaces. Combined microscale surface engineering via milling or laser etching and ion-beam surface modification allows engineering both hydrophobic and mass-transport properties directly from a bulk material rather than involving a coating. Such surfaces have potential applications in advanced heat-exchanger technology (increasing the condensation heat transfer coefficient), wind turbine technologies (delaying or eliminating ice/frost formation under extreme weather conditions), as well as for atmospheric water harvesting and condensation control on industrial heat exchangers.