Dynamic characteristics of ellipsoidal Janus drop impact on a solid surface

Abstract

Impinging Janus drops can be stably produced by adding a high-viscosity drop to a low-viscosity drop. Here, we investigate the dynamic features of bouncing Janus drops on a solid substrate for an exploration of the effects of the viscosity ratio, initial drop shape, and impact velocity on altering the hydrodynamics. Numerical results show that the low-viscosity component evolves into liquid alignment along the principal direction with the help of a preferential flow, thereby resulting in the partial detachment from the mother Janus drops. We establish a regime map of the separation ratio of the drop and discuss how the parameters affect the asymmetry in the bounce and separation behavior. The low-viscosity components can be more likely to be detached from Janus drops as the viscosity ratio, drop's ellipticity, and/or impact velocity increase. This phenomenon is explained by the residence time and breakup of symmetry in the horizontal momentum between the low- and high-viscosity components. The peculiar dynamic characteristics of the Janus drop can provide potential for various applications, such as liquid purification and separation.