Stable Generation of Single- Micron Droplets and Highly Efficient Encapsulation of Cells by Multi-Branch Channels

We have developed an efficient, stable device for generating single-micrometer-scale (1-2 µm) droplets based on the fragmentation of droplet tails by tailing. The device, created by a simple soft lithography process, induced continuous droplet fragmentation by branched channels under low-flow conditions (1–10 µL/min). The flow rate and surfactant concentration were also important factors for droplet fragmentation. Examining 10 combinations of flow rate and surfactant concentration revealed the optimal conditions, which produced droplets less than 2 µm in size at a generation rate of 61.1%. With this method, we efficiently encapsulated cell-mimicking microbeads into passively generated single-micrometer-scale microdroplets.