Droplet based microfluidics or droplet formation inside microchannels.
Droplets are formed inside channels by not mixing of two immiscible phases at a narrow section. The liquid that forms droplets is called dispersed phase or emulsion phase (the droplet phase). The liquid that covers the droplets around is called continuous phase.
Droplet size is mainly controlled by the flow rate ratio of the continuous phase and dispersed phase, interfacial tension between two phases, and the geometry of the channels used for droplet generation.
There is also term called passive and active droplet formation. Here you can find the chips all are passive droplet formation which is more common than active as it produces similar results with simpler device designs. Active droplet formation (electric, magnetic, centrifugal) often uses similar devices to passive formation but requires an external energy input.
Microfluidic channel geometry is also important for application and there are mainly three types of narrow section geometry which are; T-cross flowing, Flow focusing, and Co-Flowing. Here the chips are either T-Cross flowig or Flow focusing.