Phase separation bursting and symmetry breaking inside an evaporating droplet; formation of a flower-like pattern

TL;DR

This study investigates how phase separation and flow dynamics during droplet evaporation lead to the formation of intricate flower-like particle patterns, revealing new insights into pattern formation in evaporating liquids.

Contribution

It demonstrates experimentally that phase separation induces a unique bursting flow, causing symmetry breaking and complex pattern formation in evaporating droplets.

Findings

Phase separation causes strong entropic flow and vortices.

Flow leads to symmetry breaking and flower-like patterns.

Insights into fluid physics of phase separation.

Abstract

Pattern formation inside a liquid phase is a phenomenon involved in many different aspects of life on our planet. The droplet form of a liquid that evaporates can reveal patterns that depend on the chemistry of the droplet and the physical parameters involved. We observed a flower-like deposition pattern of micrometer-sized particles as a result of the evaporation of a droplet containing salt and a non-ionic polymer. We show experimentally that the phase separation of the polymer due to the salting-out effect causes a strong entropic flow, which manifests as vortices. The flow is called phase separation bursting flow, which leads to the axial symmetry breaking and the formation of a radially aligned flower-like pattern. We foresee that understanding the observed flow can provide insights into the fluid physics aspects of phase separation and may have implications for technical applications.