Drying dynamics of sessile-droplet arrays

We analyze the diffusion-controlled evaporation of multiple droplets placed near each other on a planar substrate. Specifically, we calculate the change in the volume of sessile droplets with various initial contact angles that are arranged in different configurations. The calculations are supplemented by experimental measurements using a technique that interprets the variable magnification of a pattern placed beneath the droplet array, which is applied to the case of initially hemispherical droplets deposited in four distinct arrangements. We find excellent agreement between the predictions based on the theory of Masoud et al. [Evaporation of multiple droplets, J. Fluid Mech. 927, R4 (2021)0022-112010.1017/jfm.2021.785] and the data gathered experimentally. 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. Our study provides not only 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.