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. [Display omitted] •A droplet jumping theory on biphilic surfaces is developed and verified•Surface structure, orientation, and air pressure are studied theoretically•The biphilic surface is optimized to maximize the droplet jumping height•Condensation heat transfer of the optimized biphilic surface is enhanced notably To maximize the droplet jumping height on a biphilic surface, Zhu et al. develop a droplet jumping theory, considering the surface structure, orientation, and air pressure. The optimized biphilic surface significantly enhances the condensation heat transfer, which benefits various thermal applications.