Study On The Dispersion Mechanism And The Dynamic Interfacial Tension In Microscale Multiphase Flow

Microfluidic is a technique to precisely control extremely small volume fluids,which is widely used in chemical synthesis,biological analysis,environmental monitoring and other fields This study had investigated the mechanism of fluid dispersion of liquid-liquid system in co-axial micro-devices,and based on this,a new micro-testing technique was developed to determine the dynamic interfacial tension in the dispersion coupling interphase mass transfer process.(1)Interface-shrinkage-driven breakup of droplets in micro-devices was investigated.Previous research of our group found that when the contact angle between the continuous phase and the dispersed phase channel is sufficiently low,the interface-shrinkage-driven breakup mechanism dominates the breakup.The present study further investigated the new mechanism in micro-devices with dispersed fluid channels of different shape.Critical contact angles in different micro-devices were determined by theoretical analysis and verified by experiments.The droplet size was measured when the two different mechanisms dominated the breakup.Mathematical models were established to predict the droplet size when the Interface-shrinkage-driven breakup took place.(2)Based on the study of flow law,a new dynamic interface tension measurement method had been developed.In present study,a microfluidic device with Laplace sensor was developed to determine the interfacial tension.It is proved that the developed Laplace sensors allow accurate measurement of the local pressure in a micro-device,which is superior to the commercial pressure sensor.The measurement range of the new method was tested by systems with constant interfacial tension.The dynamic interface tension in the dispersion coupling interphase mass transfer process was then determined.Mathematic model was also established to predict the results.The main factors that affect the transient interfacial tension were analyzed based on both the experimental and theoretical results.At the same time,the main factors affecting the dynamic interfacial tension in the process were systematically studied.