Fig. 4. An example of how the droplets could appear on the microscope picture is displayed by the black dots. Simply creating a virtual grid with its origin at the center (the red grid) of the upper left droplet does not give an accurate fit. For a better fit, the grid also needs to be translated and rotated (the blue grid). The fit of the blue grid results in much lower deviations, and gives a better representation of the droplets mutual deviation. See the ESI† for pictures of the printed droplet matrix.