Pattern-Distortion Technique: Using Liquid-Lens Magnification to Extract Volumes of Individual Droplets or Bubbles within Evaporating Two-Dimensional Arrays

Abstract

We present an experimental ``pattern-distortion'' (PD) technique which connects the shape of a liquid lens to its magnification. We demonstrate how to optimize 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 PD technique to overcome these limitations, and we 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. Thirdly, we extend the method to composite droplets systems, using it to extract the size of an air bubble trapped inside a liquid droplet.