A Novel Method (T-Junction with a Tilted Slat) for Controlling Breakup Volume Ratio of Droplets in Micro and Nanofluidic T-Junctions

We propose a novel method for producing unequal sized droplets using a titled slat in the center of a T-junctions. In the available methods for generating unequal-sized droplets such as T-junction with valve and T-junction with a heater, the minimum breakup volume ratio that is accessible is approximately 0.3 while the system of this paper can generate droplets with the volume ratio 0.05. Therefore, the manufacturing cost of the system decreases considerably because it does not need to the consecutive breakup systems for generation of small droplets. The employed method was investigated through a numerical simulation using the volume of fluid (VOF) algorithm. The simulation results are reported for micro and nano-scaled T-junctions in various tilted slat sizes, capillary numbers (a dimensionless group describes the ratio of the inertial forces to the surface tension forces) and slat angles. Our method decreases (increases) considerably the breakup time (speed of the breakup process). For example in the case Ca=0.1 and volume ratio 0.4, dimensionless breakup time of our method and the method of T-junction with valve are 0.25 and 3.6, respectively. The results revealed that the breakup length of the nanoscale T-junction is smaller than microscale and increases by increasing the slat angle in both scales. The results demonstrated the breakup volume ratio decreases by increasing the tilted slat length. Also the breakup volume ratio minimizes in a specific slat angle. The results showed the breakup time is reduced by decreasing the slat angle. We also found that the pressure drop of the system is almost independent of the system geometry.