Instability and self-propulsion of active droplets along a wall

In experiments, chemically active drops most often swim along a rigid wall, the impact of which on self-propulsion is in general completely overlooked in models. Using linear stability analysis, we demonstrate here that the proximity to a rigid surface promotes droplet propulsion as a result of the localization of the strongest interfacial flows within the thin lubrication gap separating the droplet from the wall.