Monodispersed microfluidic droplet generation by shear focusing microfluidic device

A microfluidic device designed to generate monodispersed picoliter to femtoliter sized droplet emulsions at controlled rates is presented. This PDMS microfabricated device utilizes the geometry of the channel junctions in addition to the flow rates to control the droplet sizes. An expanding nozzle is used to control the breakup location of the droplet generation process. The droplet breakup occurs at a fixed point due to the focused velocity gradient created by the nozzle shape geometry. The system not only creates monodispersed primary droplets with sizes controlled by the applied flow rates, but also generates monodispersed submicron droplets. Droplets with radii as less than 100 nm can be produced without use of surfactants. Numerical results relating flow rates to the size of primary droplets, satellite droplets and generation rates are reported.