title: Step-emulsification in a microfluidic device.
abstract: We present a comprehensive study of the step-emulsification process for high-throughput production of colloidal monodisperse droplets. The 'microfluidic step emulsifier' combines a shallow microchannel operating with two co-flowing immiscible fluids and an abrupt (step-like) opening to a deep and wide reservoir. Based on Hele-Shaw hydrodynamics, we determine the quasi-static shape of the fluid interface prior to transition to oscillatory step-emulsification at low capillary numbers. The theoretically derived transition threshold yields an excellent agreement with experimental data. A closed-form expression for the size of the droplets generated in the step-emulsification regime and derived using geometric arguments also shows a very good agreement with the experiment.
authors.affiliation: MMN, CNRS, ESPCI Paris-Tech, 10 rue Vauquelin, 75005 Paris, France.
authors.forename: Z
authors.initials: Z
authors.lastname: Li
authors.forename: A M
authors.initials: AM
authors.lastname: Leshansky
authors.forename: S
authors.initials: S
authors.lastname: Metais
authors.forename: L M
authors.initials: LM
authors.lastname: Pismen
authors.forename: P
authors.initials: P
authors.lastname: Tabeling