Spreading, rebounding, and migrating characteristics of a droplet impact on a vibrating hybrid-wettability surface

In this paper, the dynamics of droplet impact on vibrating hybrid-wettability surfaces are investigated through integrated experimental and numerical approaches, and the effects of frequency, initial phase angle, amplitude, and direction of the surface vibration on the asymmetric spreading, partial rebounding, and migration characteristics of droplet are investigated. Results indicate that the morphological evolution of post-impact droplet is significantly influenced by the vibration parameters. At small amplitudes, the droplet can remain intact, evolving similarly to that on a static surface but with different time and spatial scales. As the amplitude increases, the droplet undergoes greater deformation upon impact, leading to bottom splitting and/or upward breakup. The initial phase angle φ is a key determinant of droplet impact dynamics and interacts with frequency. Under the vertical vibration, the maximum spreading factor of the droplet is greatest at φ = 270° and smallest at φ = 90°. Over a wide range of initial phase angles, vertical vibration tends to increase the time of partial rebounding and the maximum height of the droplet. For all phase angles, droplet migration speeds are higher at a frequency of 120 Hz than that on a static surface. Horizontal vibration of the surface results in lower average migration speeds than vertical vibration at φ = 90°. At larger amplitudes, vertical vibration can promote droplet migration within a certain frequency range, while horizontal vibration may exert a suppressive effect. This study could provide valuable insights for a scientific understanding of the dynamics of droplet impacting a vibrating heterogeneous surface.