Bubble-induced symmetry breaking in droplet impact

Abstract

Symmetry typically characterizes the impact of a liquid droplet on a solid surface, where uniform spreading is followed by radial retraction. Breaking this symmetry traditionally relies on engineering surface properties. Here, we introduce an alternative approach to achieve asymmetric droplet impact by incorporating a pair of bubbles into the liquid droplet, resulting in the coexistence of spreading and retraction. The asymmetric dynamics originate from the anisotropic capillary effects that can be adjusted by varying the volume fraction of bubbles and the impact velocity. The early onset of retraction enhances upward liquid momentum, facilitating prompt droplet takeoff and significantly reducing both the contact area (up to 50%) and contact time (up to 60%). This reduction also diminishes heat exchange between the droplet and the surface. Our findings pave the way for applications that capitalize on reduced contact times through droplet engineering, eliminating the need for surface modifications.