Fig 1.

A. A droplet moving through a microfluidic channel is shown. Inset shows the size of the droplet relative to the illumination volume of a standard Confocal Fluorescence Spectroscopy (CFS) setup. B. In contrast, elongation of a droplet squeezing through a microfluidic constriction is shown. The inset shows the sheet-like Illumination volume of a Cylindrical Illumination Confocal Spectroscopy setup relative to the elongated droplet in the microfluidic constriction. C. The multilayered microfluidic device designed for the experiments in this paper is shown. A flow focusing geometry was used for droplet generation. The left panel shows droplets being generated using a food dye as the discrete phase. The rightmost panels show the retractable constriction region in either the open (left) or actuated (right) state, as described in text. (scale bar: 50 μm)