[en] In microfluidics flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. Nevertheless, the scaling laws associated to droplet length, speed and frequency could not be identified yet, owing to the large number of parameters involved (incl. complex geometry). We here present an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the dripping regime. The formation sequence is decomposed in two steps, inflation and squeezing, that vary differently according to both water and oil flow rates. These variations reveal several insights about the fluid flows in both phases. From there we infer the scaling law that relates droplet volume and frequency to the Capillary number associated to each inlet flow rate. This law involves a minimum of fitting parameters. We finally discuss the influence of inlet control (flow rate vs. pressure) and surfactants on the formation dynamics.
Disciplines :
Mechanical engineering Engineering, computing & technology: Multidisciplinary, general & others
Author, co-author :
Van Loo, Stéphanie ; Université de Liège > Département d'aérospatiale et mécanique > Microfluidique
Gilet, Tristan ; Université de Liège > Département d'aérospatiale et mécanique > Microfluidique
Language :
English
Title :
The mysterious droplet birth in a microfluidic cross junction
Publication date :
23 November 2015
Event name :
68th Annual Meeting of the APS Division of Fluid Dynamics
Event organizer :
American Physical Society - Division of Fluid Dynamics