How micropatterns and air pressure affect splashing on surfaces

TL;DR

This study explores how micro-patterned surfaces and air pressure influence the splashing behavior of ethanol drops, revealing that surface structure and ambient pressure critically affect splash dynamics.

Contribution

It provides experimental insights into how micropattern arrangements and air pressure control splashing, highlighting the role of trapped air in splash formation.

Findings

Micro-pattern arrangement significantly affects splashing outcomes.

Lowering air pressure suppresses splashing.

Trapped air is responsible for splash generation.

Abstract

We experimentally investigate the splashing mechanism of a millimeter-sized ethanol drop impinging on a structured solid surface, comprised of micro-pillars, through side-view and top-view high speed imaging. By increasing the impact velocity we can tune the impact outcome from a gentle deposition to a violent splash, at which tiny droplets are emitted as the liquid sheet spreads laterally. We measure the splashing threshold for different micropatterns and find that the arrangement of the pillars significantly affects the splashing outcome. In particular, directional splashing in direction in which air flow through pattern is possible. Our top-view observations of impact dynamics reveal that an trapped air is responsible for the splashing. Indeed by lowering the pressure of the surrounding air we show that we can suppress the splashing in the explored parameter regime.