Droplet impact on oscillating hydrophobic substrates: jetting and atomization*

Droplet impact on various surfaces has been studied extensively in literature, owing to its wide range of applications. However, impact on oscillating hydrophobic substrates has not been thoroughly investigated. This type of impact is critical in both naturally occurring processes, such as rain droplet impact on fluttering leaves or wings of insects, and in industrial applications, for manipulating droplet deposition. Our prior work on droplet impact on an oscillating hydrophobic substrate reaffirmed that substrate movement significantly affects the spreading characteristics. In this work, we will show that an oscillating substrate can also modify the recoiling dynamics of the droplet and thus affect its long-time behavior, particularly the induced jetting and subsequent atomization of the droplet. We will explore such atomization of a recoiling droplet for a range of frequency and amplitude of oscillations. Aided by experiments, we will identify the two regimes of atomization characterized by distinct timescales. Furthermore, we will endeavor to delineate these regimes and put forward a scaling analysis to predict the dynamics of post-impact atomization.