Lifting a sessile oil drop from a superamphiphobic surface with an impacting one

TL;DR

This study explores the impact dynamics of low surface tension oil drops on superamphiphobic surfaces, revealing five rebound scenarios and new lift-off mechanisms through combined experiments and simulations.

Contribution

It provides the first detailed analysis of low surface tension oil drop impacts on superamphiphobic surfaces, including novel lift-off scenarios and comprehensive numerical modeling.

Findings

Five rebound scenarios identified, four without coalescence

Two new lift-off mechanisms discovered for sessile oil drops

Simulations accurately reproduce impact dynamics and energy transfer

Abstract

Colliding drops are widely encountered in everyday technologies and natural processes, from combustion engines and commodity sprays to raindrops and cloud formation. The outcome of a collision depends on many factors, including the impact velocity and the degree of head-on alignment, in addition to intrinsic properties like surface tension. Yet little is known on the binary impact dynamics of low surface tension oil drops on a low-wetting surface. We experimentally and numerically investigate the dynamics of an oil drop impacting an identical sessile drop sitting on a superamphiphobic surface. We observe five rebound scenarios, four of which do not involve coalescence. We describe two previously unexplored cases for sessile oil drop lift-off, resulting from a drop-on-drop impact event. The simulations quantitatively reproduce all rebound scenarios and enable quantification of the velocity profiles, the energy transfer, and the viscous dissipation. Our results illustrate how varying the relative offset and the impact velocity results in controllable rebound dynamics for low surface tension drop collisions on superamphiphobic surfaces.