CoFlowing consists of using the drag of a moving fluid on a meniscus from another fluid which is immiscible with the drag and is injected through a capillary When the inner and outer flow rates are low for both fluids a system of dripping is produced just at the end of the injection tube (droplets are typically generated periodically).ube. Depending on the conditions (liquids properties, geometry of tubes,…) monodisperse microspheres, microcapsules or microfibers significantly lower than that of the fluid injected hole diameters can be obtained.

However with the higher liquid flow outside the inner fluid is more stretched into long filaments or jets liquids (jetting mode) that due to varicose instabilities breaks into droplets. In the jetting mode two regimes can be identified: the narrowing regime, in which the filament diameter decreases axially, and the widening regime, in which the filament diameter increases axially. Narrowing jets are formed when viscous forces acting on the jet surface due to the outer jet, the drag liquid, overcomes the forces of confinement due to surface tension , where the inertia of the inner fluid is negligible. In these situations, the jet narrowing occurs due to the inner speed is higher than the outer speed. On the other hand, widening jets are produced when the forces due to the inertia of the inner flow exceed confinement forces due to surface tension. By contrast, the internal fluid flows faster than the outside, which is responsible for producing a slow jet widening thereof.