Droplet–droplet vapor-mediated interactions in confined environments

Abstract

The evaporation of multiple droplets ensues ubiquitously in nature and industry. Vapor mediation caused by evaporating neighboring droplets is a demonstrated phenomenon that shows that droplets can interact with each other via the vapor in both open and confined configurations, i.e., the “shielding effect.” However, interactions between paired droplets in confined environments, more common in industrial processes, remain unexplored. In this Letter, we experimentally investigate the evaporation of water based paired sessile droplets on hydrophilic glass slides at different spacings in the absence and presence of an enclosed chamber. The results demonstrate that a confined environment significantly attenuates droplet evaporation, which intensifies with decreasing spacing between droplets. A 30%–82% increase in the droplet lifetime is found for the shortest distance studied in a confined environment, while results in an open environment are provided as a control. Both the local shielding effect and the global vapor accumulation due to confinement collaboratively induce such strong evaporation suppression. In addition, two well differentiated evaporation regimes ensue in a confined environment where the shielding effect initially dominates the evaporation suppression, whereas confinement governs the later evaporation stage. The later stage accounts for over 60% of the droplet lifetime. Such transition and further evaporation suppression, when compared to the classical shielding effect, highlights the importance of a confined environment in multiple droplet evaporation.