Figure 2.

Microfluidic Protocols for Pairing and Merging Different Droplet Populations (Aqueous Droplets in Oil)

(A) Design of the microfluidic chips.

(B–E) Images show portions of the trapping area. (B) First, a population of large droplets is injected and allowed to fill the large regions of each anchor, followed by a second population of smaller droplets. The small droplets (dark dye) then occupy the triangular regions of each anchor. Scale bar is 200 μm. (C) Flushing the device with an emulsion destabilization agent (PFO, perfluoro-octanol; Tullis et al., 2014, Akartuna et al., 2015) results in the merging of the touching droplets, which allows their contents to mix in a few seconds. Scale bar is 100 μm. (D and E) Droplet libraries can be produced in a different microfluidic device and re-injected into the trapping region. In the current example, the large droplet population contains variable concentrations of dye ranging from blue, to green, to yellow. The small droplets contain a gradient of red dye. Image of 80 anchors filled with 2 sets of colored droplets before (D) and after (E) merging. Scale bar is 1 mm.

(F and G) Quantification of the droplet colors in red, green, and blue (RGB) space before (F) and after (G) the coalescence (dot color corresponds to RGB coordinates; n_chips = 1, n_droplets = 351).

All corresponding flows can be found in Table S1.