Self-propulsion & interactions of chemically-active droplets
Chemically-active droplets are intriguingly simple system that can swim at micron scale as a result of their physico-chemical activity. In particular, droplets that slowly solubilize in a surfactant-laden solution can self-propel spontaneously as a result of the non-linear transport of surfactant molecules and micellar compounds by the solute-induced interfacial flows. Many recent experiments have reported the intriguing individual behaviour of these droplets. Furthermore, such droplets are fundamentally anti-chemotactic : they avoid regions of solute accumulation such as their own chemical trail and the vicinity of other droplets or confining walls. In experiments on multiple-droplet interactions, this results in complex avoiding trajectories. Motivated by these observations, we use theoretical modeling and numerical simulations to rationalise these individual and collective dynamics.
In this presentation, I will discuss our recent work on the nonlinear interplay of hydrodynamic and chemical interactions in droplet collisions or self-propulsion in confined environments. In particular, based on the analysis of the complete hydro-chemical interactions in a two-droplet collision, I will show how such pairwise collisions may lead to the emergence of a variety of collective dynamical regimes, as well as alignment and scattering of the droplets.