Drying dynamics of sessile-droplet arrays

We analyze the evaporation of multiple droplets placed near each other on a planar substrate. Specifically, we theoretically calculate the change in the volume of sessile droplets with various initial contact angles that are arranged in several different configurations. Our calculations are supplemented by experimental measurements for the case of initially hemispherical droplets deposited in four distinct arrangements. We find excellent agreements between the predictions based on the theory of Masoud et al. [Evaporation of multiple droplets, J. Fluid Mech. 927, R4 (2021)] and the data gathered experimentally using a technique that interprets the variable magnification of a pattern placed beneath the droplet array. Perhaps unexpectedly, we also find that, when comparing different arrays, the droplets with the same order of disappearance within their respective array, i.e., fastest evaporating, second-fastest evaporating, etc., follow similar drying dynamics. Overall, our study not only provides experimental validation of the theoretical framework introduced by Masoud et al., but also offers additional insights into the evolution of the volume of individual droplets when evaporating within closely-spaced arrays.