Research on Droplets Formation Characteristics of Modified T-Junction Microchannel Based on Inserted Capillary
A modified T-junction microfluidic chip device based on inserted capillary was proposed,and the flow visualization experiments of droplets(or bubbles)generation were carried out using micro high-speed photography.The effects of capillary insertion depth and two-phase flow rates on droplet generation characteristics were investigated,and the dynamic process of interface evolution during the droplets generation was obtained and compared with that of bubbles.The hydrodynamic mechanism of droplet stresses and fracture was revealed.The results show that this chip device can generate micro-droplets(bubbles)of controlled sizes stably,and the range of two-phase flow rate ratio are wide(2～12).The droplet generation mode is only droplet mode,and the droplet formation process experiences three stages,namely droplet head generation,head filling and necking fracture.This process is the result of the combined effects of the fluid pressure,viscous shear force and interfacial tension.Increasing the continuous phase flow rate(100～600μL/min)or increasing the capillary insertion depth(0～120μm),the generated droplet size decreases(630～201μm)and the frequency increases.There are two modes of droplet neck fracture,namely extrusion and shear.The results could provide theoretical guidance for the design and applications of droplet microfluidic chips.
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