Silicon microdevice for emulsion production using three-dimensional flow focusing

This paper presents a device that is intended to produce emulsions of liquids at a micrometer scale by using the fluidic technique that is known as flow focusing. This technique consists in the encapsulation of an inner stream by an outer liquid. By controlling both liquid flow rates, extremely thin jets can be produced, with very good control of its thickness and of the produced droplets in the emulsion. The device that is proposed in this paper performs 3-D focusing, and in contrast to previously known designs, it is integrable into bidimensional arrays, increasing the overall achievable efficiency. This paper describes the physical principle of flow focusing, presents the fabrication process of the device in silicon using standard microfabrication processes, and shows numerical simulations and experimental results, in good agreement with previously published theoretical behavior.