Insight into the Evaporation Dynamics of a Pair of Sessile Droplets on a Hydrophobic Substrate

Abstract

In this work, we have demonstrated three unique regimes in the evaporation lifecycle of a pair of sessile droplets placed in variable proximity on a hydrophobic substrate. For small separation distance, the droplets undergo asymmetric spatiotemporal evaporation leading to contact angle hysteresis and suppressed vaporization. The reduced evaporation has been attributed quantitatively to the existence of a constrained vapor-rich dome between the two droplets. However, a dynamic decrease in the droplet radius due to solvent removal marks a return to symmetry in terms of evaporation and contact angle. We have described the variation in evaporation flux using a universal correction factor. We have also demonstrated the existence of a critical separation distance beyond which the droplets in the droplet pair do not affect each other. The results are crucial to a plethora of applications ranging from surface patterning to lab-on-a-chip devices.

The shielding effect extends the lifetimes of two-dimensional sessile droplets

“…4d). Comparing (27), (30) and (a) ( b ) (35) shows that, as might have been anticipated, the lifetime of a droplet evaporating in the SS mode always lies between those of the same droplet in the CR and CA modes, i.e. t CR ≤ t SS ≤ t CA for all Ψ and θ * .…”

“…In practice, droplets rarely occur in isolation, and so it is important to understand how droplets evaporate in the presence of other evaporating droplets. Previous studies of the evaporation of multiple sessile droplets have employed a variety of experimental, numerical and analytical approaches [27][28][29][30][31][32][33][34][35][36][37][38]. The critical difference between the evaporation of single and of multiple droplets is the occurrence of the shielding effect, namely that the presence of other evaporating droplets increases the local vapour concentration, and so each droplet evaporates more slowly than it would in isolation.…”

Evaporation of multiple droplets

“…Cazabat & Guena 2010;Erbil 2012;Stauber et al 2014;Brutin & Starov 2018;Giorgiutti-Dauphiné & Pauchard 2018). While the majority of research has focused on the drying of single sessile droplets, there is broad interest in understanding the evaporation of multiple drops through experiments, simulations and theory; representative studies include Schäfle et al (1999), Sokuler et al (2010), Carrier et al (2016), Shaikeea, Jyoti & Basu (2016), Laghezza et al (2016), Castanet et al (2016), Bao et al (2018), Hatte et al (2019), Chong et al (2020) and Wray, Duffy & Wilson (2020). Among the most recent of these investigations is the theoretical analysis of Wray et al (2020).…”

Confinement suppresses instabilities in particle-laden droplets

“…1a ), vapor entrapment in the wedge formed (Fig. 2a ) by the droplet interface, channel wall and its base suppresses the global evaporation flux ( J ′) 16 , 17 . This results in an increase in local vapor concentration (Fig.…”