Coalescence of droplets on chemical boundaries

We show that emulsion droplets sedimenting toward a chemically patterned substrate can self-assemble and coalesce onto chemical boundaries, leading to a 2D growth pattern. After discussing the various features characteristic of the self-assembly process, we focus on the behaviour of a single droplet when sliding from a high contact angle area to a low contact angle area. The adsorption on the low contact angle area shall occur via two main mechanisms, depending on the interplay between droplet dynamics and wettability contrast.