Microdroplets: Drop Splitting

Drop Formation • Encapsulation • Reinjection • Drop Splitting • Picoinjection • Incubation • Detection
Sorting • Valves • Air-Triggered Dropmaking • Double Emulsification • Higher-Order Emulsification
Parallel Dropmaking • Droplet Merger

When performing a biological assay with a reagent, it is often necessary to divide the reagent into smaller portions that can then be reacted with different compounds. In droplet-based microfluidics, the module that performs this function is a droplet splitter. To split a drop, the drop is flowed into a channel that bifurcates into two channels; provided the hydrodynamic resistances of the two paths are equal and the flow rates sufficiently high, the drop will be bisected into two equal portions, as illustrated in this movie:

Droplets formed by the breakup of a liquid jet are split into two equal portions using a droplet splitter.

In most instances, splitting homogeneous single emulsions is all that's necessary; however, there are instances in which droplets containing smaller drops must also be split. These kinds of drops could be the product of an assay in which encapsulated microbes secrete an oily substance, like a biodiesel, which would form a droplet beside the microbe. Such multiple emulsions, or "emulsions within emulsions" can also be bisected using splitting devices, as shown in this movie:

Larger double emulsions can be split into very small drops by splitting them several times using a splitting array. Because the parent double emulsions are monodisperse and the hydrodynamic resistance of all paths are equal, the final, small double emulsions are also the same size.