Macrotextures-enabled self-propelling of large condensate droplets

Abstract On superhydrophobic surfaces, small condensate droplets exhibit a preferred self-propelled jumping by a coalescence-induced energy release, but large condensate droplets in several millimeters remain immobile. The accumulation of large condensate droplets leads to many problems such as shielding the growth of small droplets and increasing the thermal resistance of condensate. In this work, we present a largely unexplored strategy for enhancing the self-removal of large condensate droplets by the rational design of the millimetric macro-textured groove arrays (MGAs). In the condensation process, such macrotextures effectively create gradients in both concentration and diffusion flux of water vapor along the groove height, leading to a varying nucleation rate along the groove height. Facilitated by this preferential nucleation, large condensate droplets are objected to a Laplace pressure and undergo a self-propulsion to detach from the surface with ~50% decrease in diameter compared with the superhydrophobic surface without macro-textured groove arrays. Our findings enrich the fundamental understanding of how macrotextures regulate microscopic wetting state, and such macrotextures can be combined with the state-of-the-art micro/nano fabrication technologies for energy-water nexus applications.