Yarning droplets: Marangoni bursting with a partially soluble component

This paper is associated with a video winner of a 2021 American Physical Society's Division of Fluid Dynamics (DFD) Gallery of Fluid Motion Award for work presented at the DFD Gallery of Fluid Motion. The original video is available online at the Gallery of Fluid Motion, https://doi.org/10.1103/APS.DFD.2021.GFM.V0073.

Figure 1

Snapshots during the deposition, and subsequent spreading and evaporation, of a water-alcohol droplet (20% water, 80% IPA), laced with PMMA particles at a volume concentration of 0.1% in the original binary solution. The PMMA particles dissolve in the binary solution due to the high IPA concentration. In the mother droplet, the dissolved PMMA is transported by the outward Marangoni flow to the droplet rim. The IPA concentration at the rim is low enough for the PMMA to precipitate. In the first image for $\mathrm{t}=0\mathrm{s}$, the pipette tip to deposit the droplet is visible. We place the droplet on top of a roughly 3-mm-thick sunflower oil bath in a Petri dish, which is placed on top of a black, nonreflective hard plastic. We illuminate the experiment with an LED light source from the side and take images from above with a standard DSLR camera and a 100-mm macrolens.

Figure 2

Snapshots for a water-alcohol droplet (40% water, 60% IPA), laced with PMMA particles at a volume concentration of 0.1% in the original binary solution. The dissolved PMMA is transported towards the rim of the mother droplet, where the IPA concentration is low enough for the polymer to precipitate. The precipitation prevents any droplet shedding from the rim and instead creates a sheet, which cracks and finally splits up. In the first image for $\mathrm{t}=0\mathrm{s}$, the pipette tip to deposit the droplet is visible.