Alignment and scattering of swimming droplets

Chemically-active droplets swim in viscous flows by exploiting the nonlinear hydro-chemical coupling between the transport of a solute produced at their surface and the surface-driven flows generated by its gradients. They are intrinsically anti-chemotactic, swimming away from regions of higher solute concentrations. This includes their own wake where the slowly-diffusing solute accumulates as they move, in a mechanism that is in fact critical to their self-propulsion. As a result, swimming droplets also avoid the proximity of other droplets and/or their chemical trails, leading to complex avoiding trajectories and collective dynamics.

Building upon our complete modeling of the nonlinear hydrochemical problem for axisymmetric droplet interactions, this presentation will introduce a reduced order analysis of general (oblique) droplet collisions, and show such interactions may lead to either alignment or scattering of their trajectories.