Linear stability of a draining film squeezed between two approaching droplets

Droplet confinement and leakage: Causes, underlying effects, and amelioration strategies

“…Droplets created in a microfluidic channel are not necessarily stable when they come into contact with each other, even when a surfactant is present. When droplets come together during flow, the oil between the surfactant monolayers at the droplet surfaces is depleted 49,50 in an analogous manner to DIB formation. When the lead droplet moves away, it causes localised destabilisation between the droplets which, in turn, can initiate merging.…”

Avalanches of coalescence events and local extensional flows – Stabilisation or destabilisation due to surfactant

“…Marangoni stresses are probably significant in such events through their action on surface mobility, but assessment of their real contribution would require detailed analysis using numerical simulation, not included in the present work. A few groups have solved the implicit Euler equations for the time dependent flow numerically, with surfactant diffusion at drop surfaces and in the bulk [24,22,25], whereby effects of non-axisymmetric perturbations [37] are generally neglected. Also, one should be careful with assumptions that appear natural, since in certain instances it is predicted [25] that surface diffusivity can still have significant effect for a surface Péclet number Pe s as high as 1000, Pe s being defined as the ratio of the surface diffusivity to the surface shear rate.…”

Viscous coalescence of expanding low-viscosity drops; the dueling drops experiment

“…c ∼ a). Recent linear stability studies of a draining film, shaped as a flat disk, proved that the most unstable mode is non-axisymmetric with a characteristic length scale equal to the disk radius a [18]. However, even if the film adopts a dimpled configuration, the relevant curvature for the stabilizing capillary force is the curvature in the circumferential direction.…”