Snap evaporation of droplets on smooth topographies

Wells, Gary G.; Ruiz-Gutierrez, Elfego; Le Lirzin, Youen; Nourry, Anthony; Orme, Bethany V.; Pradas, Marc and Ledesma-Aguilar, Rodrigo (2018). Snap evaporation of droplets on smooth topographies. Nature Communications, 9, article no. 1380.

DOI: https://doi.org/10.1038/s41467-018-03840-6

Abstract

Droplet evaporation on solid surfaces is important in many applications including printing, micro-patterning and cooling. While seemingly simple, the configuration of evaporating droplets on solids is difficult to predict and control. This is because evaporation typically proceeds as a “stick-slip” sequence—a combination of pinning and de-pinning events dominated by static friction or “pinning”, caused by microscopic surface roughness. Here we show how smooth, pinning-free, solid surfaces of non-planar topography promote a different process called snap evaporation. During snap evaporation a droplet follows a reproducible sequence of configurations, consisting of a quasi-static phase-change controlled by mass diffusion interrupted by out-of-equilibrium snaps. Snaps are triggered by bifurcations of the equilibrium droplet shape mediated by the underlying non-planar solid. Because the evolution of droplets during snap evaporation is controlled by a smooth topography, and not by surface roughness, our ideas can inspire programmable surfaces that manage liquids in heat- and mass-transfer applications.

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