Micro-droplet formation with non-Newtonian solutions in microfluidic T-junctions with different inlet angles

T-junctions with various inlet angles (θ=30°, 60°, 90°, 120° and 150°) were employed to produce microdroplets. Experimental results showed that the inlet angles play an important role in controlling the droplet size and the T-junction with an inlet angle of 90° always generating the largest droplets for a given continuous phase flow rate. The results for the droplet diameters were separated into two groups, based on the range of the inlet angles (acute angles of 30°, 60° and 90°, and obtuse angles of 90°, 120° and 150°). For the acute inlet angles, the droplet size was larger for an inlet angle of θ=30° than for an inlet angle of θ=60°. For the obtuse inlet angles, the diameter of droplets produced by T-junctions with inlet angles of 120° and 150° were similar in size but smaller than that for 90°. The effect of flow rates of both phases on the droplet formation mechanism was discussed. Water and non-Newtonian xanthan gum and PEO (Polyethylene oxide) solutions were used as the dispersed phase and the differences in droplet sizes were studied.