Evaporation of Droplets on Strongly Hydrophobic Substrates

Abstract

The manner in which the extreme modes of droplet evaporation (namely, the constant contact radius and the constant contact angle modes) become indistinguishable on strongly hydrophobic substrates is described. Simple asymptotic expressions are obtained which provide good approximations to the evolutions of the contact radius, the contact angle, and the volume of droplets evaporating in the extreme modes for a wide range of hydrophobic substrates. As a consequence, on strongly hydrophobic substrates it is appropriate to use the so-called "2/3 power law" to extrapolate the lifetimes of droplets evaporating in the constant contact radius mode as well as in the constant contact angle mode.

Evaporation of water: evaporation rate and collective effects

“…2 (b) for the superhydrophobic substrate, we observed the radius to decrease continuously, with no indications of contact line pinning. Since the speed of retraction is slow, as measured for example by the capillary number (Larson 2014), the dynamic contact angle is close to its constant equilibrium value, and the mode of evaporation is one of constant contact angle (Stauber et al 2015). As is well known (Cazabat & Guéna 2010;Stauber et al 2015), combining the evaporation rate (2.5) with the formula for the volume of a small (i.e.…”

“…In fact, in the regime of slow evaporation considered here the evaporation is quasi-steady (Cazabat & Guéna 2010;Stauber et al 2015), hence evaporation rates are defined by the instantaneous drop shapes. As we will explain in more detail below, linear scaling with size results from the evaporation rate being governed by the diffusive transport through the vapor (Deegan et al 1997;Bonn et al 2009).…”

On the lifetimes of evaporating droplets with related initial and receding contact angles

“…In particular, the diffusion-limited model predicts that when 0 ≤ θ < π/2 the flux is largest (theoretically integrably singular) at the contact line and smallest at the apex of the droplet (i.e., at r = 0), when θ = π/2 the flux is uniform and given by J = D(c sat − c ∞ )/R, and when π/2 < θ ≤ π the flux is largest at the apex of the droplet and smallest (theoretically zero) at the contact line (see, for example, Stauber et al 35 ).…”

Diffusion dominated evaporation in multicomponent lattice Boltzmann simulations

“…There are numerous theoretical [6][7][8] and experimental [4,9] studies of fluid evaporation. While most theoretical studies are limited to the macroscopic scale, experiments suffer from difficulties that arise by tuning the individual microscale properties of fluids.…”