Dripping and Jetting in a Co-flowing Fluid Stream

We present preliminary data on drop formation from a nozzle in a co-flowing fluid. This problem has been addressed for cases where the outer fluid is a gas or a stationary viscous fluid. We observe that drop formation is affected by the co-flowing fluid. We focus on the dripping-jetting transition, jet size and shape, and drop sizes. Finally, we relate the physics of drop formation to a recently reported microcapillary device (1,2) that generates monodisperse double emulsions. \newline \newline (1) A. S. Utada, E. Lorenceau, D. R. Link, P. Kaplan, H. A. Stone, D. A. Weitz, Science 308, 537 (2005) \newline (2) E. Lorenceau, A. S. Utada, D. R. Link, G. Cristobal, M. Joanicot, D. A. Weitz, Langmuir in press, (2005).