Symmetry breaking in evaporating droplet and formation of flower-like pattern

Abstract When a droplet evaporates, the components dissolved within it can deposit in patterns that reflect the underlying fluid dynamics. We report the formation of a flower-like deposition pattern of micrometer-sized particles from an evaporating droplet containing salt and polyethylene glycol (PEG). Using particle tracking and flow-field analysis, we show that this pattern arises from spontaneous symmetry breaking driven by vortical flows, which redistribute particles into radially aligned petals. The emergence of these vortices depends critically on the simultaneous presence of salt and polymer; in the absence of either component, no such flows are observed. We suggest that the salting-out effect, which induces phase separation of the polymer during evaporation, may generate the flows responsible for the observed symmetry breaking. This work demonstrates that a simple multicomponent droplet can produce complex, non-axisymmetric patterns, with potential implications for understanding how phase separation influences pattern formation and transport processes in biological and natural systems.