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Microfluidic approaches for the determination of interfacial tension and viscosity of liquid-liquid systems still face some challenges. One of them is liquid-liquid systems with low interfacial and high viscosity, because dripping flow in normal microdevices can’t be easily realized for the systems. In this work, we designed a capillary embedded step T-junction microdevice to develop a modified microfluidic approach to determine the interfacial tension of several systems, specially, for the systems with low interfacial tension and high viscosity. This method combines a classical T-junction geometry with a step to strengthen the shear force further to form monodispersed w/o or Aqueous Two-phase (ATP) droplet under dripping flow. For systems with low interfacial tension and high viscosity, the operating range for dripping flow is relative narrow whereas a wider dripping flow operating range can be realized in this step T-junction microdevice when the capillary number of the continuous phase is in the range of 0.01 to 0.7. Additionally, the viscosity of the continuous phase was also measured in the same microdevice. Several different systems with an interfacial tension from 1.0 to 8.0 mN·m−1 and a viscosity from 0.9 to 10 mPa·s were measured accurately. The experimental results are in good agreement with the data obtained from a commercial interfacial tensiometer and a spinning digital viscometer. This work could extend the application of microfluidic flows.

The kinetics of p-nitrotoluene nitration with mixed acid is important to industrial process design and safety control. However, it's difficult to acquire accurate kinetic data and no kinetics study has ever been reported before because of fast, highly exothermic and heterogeneous characteristics. In this work, a continuous-flow microreactor system including a micromixer, a capillary reactor and an online quenching module was designed to carry out the nitration under a homogeneous reaction condition. The homogeneous nitration can completely eliminate mass transfer resistance between phases, and accurately control reaction temperature and residence time in the continuous-flow microreactor system. The observed reaction rate constants separately based on HNO3 and NO2+, pre-exponential factor and activation energy of p-nitrotoluene nitration were obtained and a general method was established to collect kinetics data for such a kind of fast and highly exothermal nitration reactions.