Condensation-Mediated Suppression of Lamella Rupture during High Weber Number Droplet Impact on Cold Superhydrophobic Surfaces

Abstract Droplet impact on superhydrophobic surfaces underpins a range of interfacial transport processes, particularly in anti-icing applications. While impact dynamics on dry surfaces are well-established, the coupled effects of low surface temperature and ambient humidity introduce condensate-mediated interactions that remain poorly understood, especially at high Weber numbers. Here, we explore the droplet impact on superhydrophobic surfaces with temperatures ranging from near-freezing to ambient conditions and a controlled range of relative humidities over higher Weber numbers. On dry surfaces, film rupture at high Weber numbers reduces the contact time significantly. In contrast, under cold and humid surface conditions, condensate microdroplets increase the contact angle hysteresis, slowing lamella retraction and thereby extending the contact time even in the presence of film rupture. The maximum spreading diameter depends strongly on the surface temperature and relative humidity. At lower temperatures and higher humidities, both the maximum spreading diameter and the corresponding spreading time decrease because of the enhanced viscous dissipation and contact line pinning. Additionally, film rupture is suppressed in the presence of condensate microdroplets. We propose that these microdroplets modify the effective surface roughness and lamella properties, preventing the lamella from satisfying the criteria for hole nucleation and thereby reducing the likelihood of rupture. A nucleation-based model incorporating changes in the lamella free energy is used to support the experimentally observed suppression of film rupture. These findings highlight the critical role of coupled thermal and environmental conditions in governing postimpact dynamics on superhydrophobic surfaces.