Droplet jumping physics on biphilic surfaces with different nanostructures and surface orientations under various air pressure conditions

Suffering from the adhesion of condensing water droplets, surface condensation performance is severely degraded. On a biphilic surface, condensing droplets efficiently nucleate while spontaneously being effectively removed from the surface due to the coalescence-induced droplet jumping phenomenon, significantly improving the surface condensation performance. However, it remains a challenge to appropriately tune the biphilic surface structure to maximize the droplet jumping performance and improve the condensation. Here, we report an experimentally verified droplet jumping theory that can optimize the biphilic surface structure, maximizing the droplet jumping height on the biphilic surface. Effects of surface orientation and air pressure are also investigated. The heat flux on the optimized biphilic surface can be enhanced by ∼43% and ∼139% compared with that on the superhydrophobic surface and a normal copper plate under atmospheric conditions, respectively, while that of the water collection flux can be improved by ∼61% and ∼273%, respectively.