Stability Analysis and Fabrication Process of a Multiple Flow Focusing Microdevice Built in SU-8

In this paper, the design and fabrication process of a three-dimensional and multiple flow focusing device, intended for low-cost mass production of liquid-liquid emulsions, are reported. The material used to build the device is the SU-8 epoxy photoresist because of its adequate properties for flow focusing technology. At first, the behavior of the device is unstable because of interaction between neighboring devices, which produces a undesirable operation. This behavior is simulated and analyzed, and a solution to solve this instability is chosen from these simulations. From the simulations, a graphical representation of stable and unstable behaviors as a function of flow rates of both fluids is obtained. Finally, the new design that solves the instabilities is simulated and its fabrication process is reported. A stable, multiple three-dimensional flow focusing device is achieved with the chosen solution.