Continuous generation of femtolitre droplets using multistage dividing microfluidic channel

We describe a novel method for generation of femtolitre-order monodisperse droplets using a multistage dividing microfluidic channel. A droplet is uniformly divided into 16 parts in a four-stage microfluidic channel without the need for external equipment. The droplets become smaller as the cross-junction part becomes narrower (range from 87.8 to 9.05 pL). Central micropillar structures at each bifurcation reduce the difference in the channel resistance throughout the microchannel between two side-channel that is divided by micropillar structures, which enables the equivalent division of femtolitre-order-volume droplets. After the fourth bifurcation, the minimum radius of a daughter droplet is 5 μm (ca. 524 fL) and the coefficient variation is 0.51%. The generation rate is 3800 droplets/s in a single-droplet generation line.

► Thousands of femtolitre-volume droplet are passively formed in microfluidic device.
► Droplet is divided into half volume at each bifurcation using pillar structure.
► Droplet volume is controlled by flow velocity and channel size of cross-junction part.