Experimental and computational analysis of droplet formation in a high-performance flow-focusing geometry

Detailed experimental and simulation studies are performed and presented to further substantiate the previously reported high-performance flow-focusing geometry for droplet generation. In this geometry, water-in-oil droplets are formed through a three-dimensional (3D) circular orifice directly integrated inside a silicon microchannel. The geometry ensures controlled breakup of droplets for a wide range of flow rates. Simulations are provided using computational fluid dynamics software to elucidate the flow behavior nearby the 3D circular orifice. In addition, experimental results on the droplet generation characteristics are obtained both from the 3D circular constriction as well as quasi-2D (2D) rectangular constriction that are typically used in flow-focusing devices. Direct comparison of these results further supports the claim that droplets formed by the 3D circular orifice show noticeably increased sensitivity against the flow rate of the continuous oil-phase both in droplet size and generation frequency.