Long-Term Superhydrophobicity at Copper-Based Interface with Micropillar Structure for Droplet Condensation

Phase-change heat transfer is an effective technology for dissipating heat, and one of the key factors to influence the process is the wetting behaviour of the interface. Therefore, preparing a stable metal-based superhydrophobic interface to keep droplet on the Cassie state is of significant importance. In this study, the Cassie state model is optimised as a means of designing the hill-like curved micropillar array with tunable diameter, space, and height. This results in the achievement of a stable copper-based superhydrophobic interface. Non-silicon microelectromechanical systems (MEMS) fabrication process is then used to create a uniform and robust copper-based microstructure superhydrophobic interface. By regulating the diameter and space, the micropillar array with a space-diameter ratio greater than 2 exhibits a 48.2% improvement in hydrophobicity compared to a smooth copper surface, in accordance with theoretical calculations. In addition, by varying the height of the micropillar, the interface can exhibit the lotus effect with the height-diameter ratio greater than 0.5, thereby enhancing the liquid exchange rate at the condensation interface.