Dynamics and universal scaling law in geometrically-controlled sessile drop evaporation

Abstract

The evaporation of a liquid drop on a solid substrate is a remarkably common phenomenon. Yet, the complexity of the underlying mechanisms has constrained previous studies to spherically symmetric configurations. Here we investigate well-defined, non-spherical evaporating drops of pure liquids and binary mixtures. We deduce a universal scaling law for the evaporation rate valid for any shape and demonstrate that more curved regions lead to preferential localized depositions in particle-laden drops. Furthermore, geometry induces well-defined flow structures within the drop that change according to the driving mechanism. In the case of binary mixtures, geometry dictates the spatial segregation of the more volatile component as it is depleted. Our results suggest that the drop geometry can be exploited to prescribe the particle deposition and evaporative dynamics of pure drops and the mixing characteristics of multicomponent drops, which may be of interest to a wide range of industrial and scientific applications.

Evaporation of Sessile Water Droplets on Horizontal and Vertical Biphobic Patterned Surfaces

“…This is surprising, given that previous studies observed an increase in evaporation flux with decreasing contact angles. 4,5 We attribute this to the non-homogeneous concentration gradient in the gas phase, which is the rate-limiting factor.…”

“…The evaporation of droplets has shown great potential in a myriad of industrial applications, including spray coating, 1,2 spray cooling, 3,4 inkjet printing, 5,6 bio-sensing 7 and thermal management of electronic devices. [8][9][10] Droplet evaporation is affected by many parameters, such as substrate thermal properties, [11][12][13] roughness, 14,15 and wettability.…”

Travelling-wave spatially periodic forcing of asymmetric binary mixtures

“…Examples (based on numerical solutions) of both limits are shown in Figure 1. Panel (a) corresponds to a case where the regular perturbation theory holds and the resulting reduced first-order model (7) are valid. Hence, for an appropriate (small) value of , there is very close agreement between the full third-order problem and the first-order model solution (the first-order model corresponds to → 0).…”

“…We determine parameter regimes wherein the reduced-order (7) is valid. The approach is twofold: we use numerical solutions to map out a parameter space where the reduced-order model is valid.…”

Topological transitions of surface microdroplets

“…We can see that the velocity of the experimental point is always higher than the one predicted. This underestimation can be due to a considerable enhancement of the dissolution rate that can be expected due to the curved geometry during the zipping-depinning process [52], which has been ignored in our calculations. Additionally, it can be influenced by the underestimation of the volume brought about by our simple geometrical model.…”