Experimental and simulation study of flow patterns in the combined flow focusing and T-junction device

Abstract

This paper presents a study of droplets generation, particularly examining different regimes or patterns of the flow by a novel device that combines two principles for droplets generation (flow focusing and T-junction (FF-TJ)) under different flow conditions, named combined FF-TJ. The study involves both experiment and simulation. From the experiment mineral oil and distilled water, three regimes (namely continuous regime, jetting regime, and squeezing regime) were found. This finding was subsequently confirmed by the simulation, which thus also gave a validation of the simulation system. The simulation was further employed to study the relationship among various parameters, including the velocities of the flows (i.e. sheath flow, middle flow, and crossflow) in the context the three regimes. We observed that the three regimes were determined by two critical values of the velocity of the middle flow, U m1 and U m2 . Interestingly, it was further found that the two critical values remained the same, independent of the velocity of the sheath flow. We further investigated the effects of the velocity ratio (the middle flow to the sheath flow, R m/s ) and the capillary number of the crossflow on the microsphere diameter. Overall, this paper presents a comprehensive study of the FF-TJ device and the associated implications for microsphere or droplet generation.

Recent advances in microfluidics-enabled controlled reaction, assembly and exfoliation of inorganic nanomaterials

“…3b, which outlines the design of a microsphere generation device known as the flow focusing and T-junction (FF-TJ) device. 69 It operates using the principles of flow focusing and a T-junction, which rely on using two fluids, the outside continuous flow liquid and the inside dispersed flow liquid. The continuous flow disrupts the dispersed flow liquid and creates shear stress to separate the dispersed liquid and generate droplets.…”

“…Although flow focusing produces microspheres, in the FF-TJ, the purpose of the flow focusing segment is to adjust the size of the middle flow by varying the flow ratio between the inner and outer liquids to control the microsphere size. 69 Other passive microsphere generation methods exist, such as T-junctions and flow-focusing devices by themselves and microemulsion techniques, 67 and another form of flow behavior that can be achieved in microfluidic devices includes spiral flow created by slanted grooves on the capillary walls.…”

Numerical Study on the Formation and Solidification of LMPA Microdroplet in a Microfluidic Device

“…T-junction or flow-focusing microfluidic systems are able to continuously generate micro-scale droplets with a uniform diameter (Stone et al, 1986;Fu et al, 2012;Jamalabadi et al, 2017;Li et al, 2019a;Outokesh et al, 2022). Thus, in recent years, several experimental and numerical methods have been used to study and evaluate the droplet formation process and its influencing process based on these devices (Li et al, 2019a;Cui et al, 2019;Lei et al, 2020;Outokesh et al, 2022). Computational fluid dynamics (CFD) simulation provides a method for an indepth understanding of this complicated process.…”