Influence of Evaporation on Contact Angle

Abstract

The evaporation of sessile drops of water and n-decane placed on various substrates has been studied using a projection method. Drop dimensions and contact angle have been measured as a function of time. The first stage of the experiment corresponds to a saturated atmosphere; then, when evaporation is allowed to occur, two or three different stages appear (depending on the surface roughness). For the first of these, a model is proposed which allows us to calculate the coefficient of diffusion of the liquid vapor in air.

Instantaneous distribution of fluxes in the course of evaporation of sessile liquid droplets: Computer simulations

“…In the presence of contact angle hysteresis the latter process occurs in three steps [6,7]. During the first step evaporation proceeds with a constant radius of the droplet base, L, and decreasing contact angle, θ, until the contact angle reaches the static receding value, θ r .…”

Evaporation of Sessile Water Droplets in Presence of Contact Angle Hysteresis

“…(2.18) and (2.20) are validated against available experimental data extracted from literature sources [5,7,45]. The characteristic time of the process can be calculated using Eq.…”

“…For the experiments presented in paper [5] (water on polished epoxy surface) it is impossible to calculate T av because the humidity of ambient air was not specified in their experiments. For water on corning Water on polished epoxy surface [5] Theory (θ ad =0.923; t ch =1267 s)…”

“…Hence, Water on polished epoxy surface [5] Water on corning glass 7740 [7] Water on PMMA [45] Water on PET [45] Theory …”

“…It has been established [5,41] that in the presence of contact angle hysteresis the evaporation of a sessile droplet in non-saturated vapour atmosphere can go through four consequent stages: (0) a spreading until the value of static advancing contact angle, θ ad , is reached; (I) evaporation proceeds with a constant contact area and decreasing contact angle, θ, until the contact angle reaches the receding value, θ r ; (II) evaporation with a constant contact angle, θ r , and decreasing radius of the contact line, L; (III) evaporation with decrease of both L and θ until droplet disappears. During the first stage (0) the evaporation can be neglected and, hence, can be described using conventional hydrodynamic approach [43].…”