Splitting behaviors of droplets in fractal tree-shaped microchannels

Droplet splitting in fractal tree-shaped microchannels is studied experimentally in this work. Four flow patterns of droplets splitting in fractal tree-shaped microchannels are distinguished according to the level of bifurcations that all the droplets breakup. The self-similar variation of the droplet pressure and velocity are discussed. And the effect of capillary number and droplet size on the size distribution of daughter and granddaughter droplets are examined quantitatively. The results indicate that the tree-shaped networks with φ =  90° are better than the φ =  120° for the sequential breakup of droplets. Asymmetry in the breakup accumulates as the droplets enter high-level branch channels. Increasing Ca is an effective approach in maintaining the monodispersity of daughter and granddaughter droplets since non-breakup regime is eliminated in the low-levels of branch channels. The performance of splitting droplets is deteriorated as the mother droplet size decreases, that increasing inactive branch channels are observed.