Microfluidic Droplet Generation Device with Flexible Walls

Co-flow droplet microfluidics systems are used to generate discrete or dispersed microdroplets of one fluid (d-phase fluid) inside another immiscible fluid (continuous or c-phase fluid). Droplet sizes plays an important role for the physical and/or chemical attributes of a system. A planar device was developed with controllable c-phase channel width to tune droplet sizes. We found that the diameter of droplets was inversely proportional to the root square of channel width in constant c-phase velocity. This was due to the increased shear force due to the channel width decrease and controlled droplet size. Also, the effect of channel height on droplet size was examined. The results showed that at lower channel height, smaller droplets were generated because c-phase hardly bypassing the droplet enhanced the wall effect. The change of droplet size at constant c-phase flow rates was more than that at constant c-phase velocity. A decrease in channel width at constant flow rate not only increases the wall effect, but also increases the axial velocity which leads to a stronger drag force. The range of droplets generated in the developed device was exceptionally wider (by 111%) compared to the reported device in the literature.