Wetting dynamics of volatile mixtures: Impact of Dispersion and Phase separation

Wetting and evaporation of sessile droplets of multi-component liquids is a ubiquitous natural and industrial process, relevant, e.g., for painting and printing, for cleaning and drying of semiconductor surfaces, or for the deposition of pathogens.

Typically, the rate of evaporation is not uniform across sessile droplets, but has a sharp peak at the contact line. This promotes, for instance, the so-called coffee ring effect, an enrichment of solute particles at the edge of the evaporating droplet. For liquid mixtures, this causes compositional gradients that peak at the contact line where they may alter the wetting behavior. Most notably, different liquids have different surface tensions, leading to so-called Marangoni flows that may cause a spreading or contracting motion, depending on the contrast of volatilities and surface tensions.

In this talk I will discuss our recent work on the wetting dynamics of droplets of volatile binary and ternary liquid mixtures. I will explain the wetting behavior of these mixtures quantitatively and demonstrate how ternary mixtures may be used for a dynamic reversal of the wetting motion, e.g. to dissolve and collect residues from surfaces.

Further, I will demonstrate how these phenomena may be used to overcome contact line pinning on topographically patterned surfaces, and how phase separation of partially miscible liquids impacts their wetting dynamics.