Structured deposition by Marangoni flows in droplets: thermo-capillary fingering

A drying, pinned droplet induces aninhomogeneous evaporation rate sets up a capillary flow, directed towards the edges. This flow drags all suspended matter to these edges and creates an accumulation, commonly referred to as the “coffee ring effect” All matter, even present surfactants move to the edge. The heap up and adsorption at the contact line create a surface tension gradient at the interface and induce a Marangoni stress, resulting in a recirculating flow in the droplet As time increases, these vortices become unstable and zones with a distinctly higher concentration of tracer particles start to move outward, in distinct finger-like depositions.status: publishe