The evaporation dynamics of multiple droplet arrays is important in inkjet printing and spray coating, where cooperative "shielding" effects increase overall evaporation time. However, current measurement methods provide limited information on how individual droplets contribute to the overall dynamics. In this work, we present a simple interferometric technique for precise measurements of droplet evaporation rates which is not possible via traditional approaches. We validate the technique on a single droplet. We then extend our analysis to ordered and random 2-D arrays of droplets. We demonstrate that the evaporation rate is highly dependent on the position of the droplet within the array and its confinement. The more confined droplets exhibit lower evaporation rates. Our results of 10 different configurations and well over 100 droplets are in good quantitative agreement with a recent analytical model of co-operative evaporation rates. Our approach opens up possibilities for studies of collective evaporation effects, including in areas of current importance such as sneezes and exhaled breath.

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)] 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.

We present an experimental "Pattern Distortion" technique which connects the shape of a liquid lens to its magnification. We demonstrate how to optimise the technique for arbitrary droplet sizes and optical configurations, and demonstrate its widespread utility in three distinct situations. Firstly we consider multiple sessile droplets. Although ubiquitous in nature, understanding of their complex interactions is limited, partly due to experimental limitations in determining individual droplet volumes for arbitrary configurations. We use the Pattern Distortion technique to overcome these limitations and find excellent agreement between our experimental data and three recent theoretical models. Secondly, we show how our technique can be used to inform the design of liquid lenses and thirdly we extend the method to composite droplets systems, using it to extract the size of an air bubble trapped inside a liquid droplet.