Geometrically Mediated Breakup of Drops in Microfluidic Devices
Howard Stone and coworkers describe two techniques for breaking up droplets in an emulsion using microfluidic devices. The first method makes use of a "T-junction," in which a droplet flows down a channel that abruptly branches out into two channels in an orthogonal direction. The second method involves placing an obstacle in the droplet's path. Also notable is the article's analysis of the conditions under which a droplet encountering a T-junction will actually break up.
The process of creating droplets in the first place was previously described by Steve Quake and coworkers , who mixed two immiscible liquids in a similar T-junction microfluidic circuit, made from PDMS using soft lithography . Stone and coworkers used oil (hexadecane) and water to make the emulsion, including a surfactant to lower the surface tension between the two liquids in order to stabilize droplets.