Evaporation of Active Drops: Dynamics of Punctured Drops and Particle Deposits of Ring Galaxy Patterns

TL;DR

This paper investigates the evaporation behavior of active nematic drops containing self-migrating particles, revealing unique puncturing and ring-like deposit patterns driven by activity, with implications for cooling, bio-applications, and 3D printing.

Contribution

It introduces a novel understanding of evaporation dynamics in active nematic drops, highlighting the role of activity-induced stresses and identifying key parameters influencing deposit patterns.

Findings

Active nematic drops exhibit puncturing during evaporation.

Distinct ring-galaxy-like particle deposits form post-puncture.

Three non-dimensional parameters control evaporation and deposit patterns.

Abstract

Active drops refer to drops with the ability to self-migrate: these drops typically attain this ability by virtue of containing of active particles that derive energy from their environment and undergo directed motion inside the drops, thereby creating intricate stress distribution within these drops. Here we describe the evaporation dynamics of a slender active nematic drop. The stresses induced by active nematic particles present within the drop enables fascinating drop evaporation dynamics, consisting of an initial pinned stage and a late runaway stage. Unlike regular drops, during the pinned stage (for extensile drops) the drops encounter puncturing at their centers, followed by a receding motion of the newly formed inner contact line with the liquid flux pushing the (nematic) particles towards the inner and the outer contact lines: the result is the formation of a unique ring-galaxy-like particle deposition pattern. We identify three non-dimensional parameters, representing the activity, the aspect ratio, and the receding contact angle, which dictate the occurrence of puncturing, the overall evaporation time, and the possible deposit patterns for the extensile drops and the contractile drops. Finally, we argue that such unique evaporation and particle deposition dynamics can be leveraged for altering lifetime of drops for cooling and bio-applications and creating customized thin film deposits with potential 3D printing applications.