Provided are microfluidic designs and methods for rapid generation of monodisperse nanoliter volume droplets of
reagent / target (e.g., molecule or
cell) mix in
emulsion oil. The designs and methods enable high-
throughput encapsulation of a single target (e.g.,
DNA /
RNA molecules or cells) in controlled size droplets of
reagent mix. According to various embodiments, a microfabricated, 3-valve pump is used to precisely meter the volume of
reagent / target mix in each droplet and also to effectively
route microparticles such as beads and cells into the device, which are encapsulated within droplets at the intersection of the reagent channel and an oil channel. The
pulsatile flow profile of the microfabricated pumps provides
active control over droplet generation, thereby enabling droplet formation with oils that are compatible with biological reactions but are otherwise difficult to form emulsions with.