Oil-on-water droplets faceted and stabilized by vortex halos in the subphase

Yitan Li, Amir A. Pahlavan, Yuguang Chen, Song Liu, Yan Li, Howard A. Stone, Steve Granick

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

For almost 200 y, the dominant approach to understand oil-on-water droplet shape and stability has been the thermodynamic expectation of minimized energy, yet parallel literature shows the prominence of Marangoni flow, an adaptive gradient of interfacial tension that produces convection rolls in the water. Our experiments, scaling arguments, and linear stability analysis show that the resulting Marangoni-driven high-Reynolds-number flow in shallow water overcomes radial symmetry of droplet shape otherwise enforced by the Laplace pressure. As a consequence, oil-on-water droplets are sheared to become polygons with distinct edges and corners. Moreover, subphase flows beneath individual droplets can inhibit the coalescence of adjacent droplets, leading to rich many-body dynamics that makes them look alive. The phenomenon of a “vortex halo” in the liquid subphase emerges as a hidden variable.

Original languageEnglish (US)
Article numbere2214657120
JournalProceedings of the National Academy of Sciences of the United States of America
Volume120
Issue number4
DOIs
StatePublished - Jan 24 2023

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Marangoni flow
  • active matter
  • droplets
  • nonequilibrium

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