Flexible Fractal Integration of Microfluidic Modules for Controllable Mass Production of Monodisperse Microdroplets

Modular microfluidic integration, which is powerful for controllable mass production of droplets, usually suffers from limited dimension choice and complicated calculations. Here, a generalized and simple strategy based on stepwise nesting of basic fractal networks to create nested flow distribution networks for modular microfluidic integration is proposed. The H-shaped fractal network with a symmetrical flow-resistance setup and the widely used ladder network are respectively used as the typical basic fractal network and the control group. Compared to the control group, the nested fractal networks enable more flexible choices of microchannel dimensions for uniform flow distribution. The integrated fractal modular device with 256 flow-focusing microchannels can massively produce droplets with size monodispersity remarkably better than those from the control group device and can create monodisperse Ca-alginate microspheres from viscous liquids. This strategy provides a rational scale-up guideline to create modular devices with uniform flow distributions for mass production of monodisperse microdroplets.