Evaporation of one and more multi-component drops

The evaporation of multi-component sessile droplets is key in many physico-chemical applications such as inkjet printing, spray cooling, and microfabrication. Past fundamental research has primarily concentrated on single drops. Here, we experimentally explore the effect of neighboring drops on the evaporation process, employing direct imaging, confocal microscopy, and μPTV. In contrast to the Marangoni flow in an isolated drop, the Marangoni flow in neighboring droplets is no longer axisymmetric. The symmetry breaking is mediated by the vapor phase. We explore the dependence on the distance between droplets and the ambient relative humidity. When unpinned, it is known that Marangoni contraction will move the centers of the drops closer to one another. When pinned, however, we find that this effect is reversed: the centers of the drops move away from each other as they partially de-pin. We present our explanation of this remarkable effect.