CFD study and experimental verification of droplet formation characteristics in a flow-focusing microfluidic device

Q: What is the main goal of this study?

To numerically investigate droplet formation in a 3D flow-focusing microchannel and validate the results experimentally using a fabricated device.

Q: Which parameters are studied, and what outcomes do they influence?

Injection angle, continuous-phase viscosity, flow velocities, and interfacial tension are varied to assess flow regimes, droplet size, formation frequency, and breakup time.

Q: How does injection angle affect droplet detachment and size?

At acute angles, increasing the injection angle delays detachment and produces larger droplets with greater interdroplet distance; at obtuse angles, larger angles slow formation and produce smaller droplets with shorter spacing.

Sep 29, 2026

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Numerical simulations are used to investigate droplet formation in a three-dimensional flow-focusing microchannel, and the predictions are validated with a lithographically fabricated device (error < 4%). The work examines how injection angle, continuous-phase viscosity, flow velocity, and interfacial tension affect two-phase flow regimes, instantaneous fields, droplet size, formation frequency, and breakup time. Acute angles delay detachment and yield larger droplets; obtuse angles reduce size and spacing. Repeatability tests (coefficient of variation < 1%) confirm high stability, providing practical design guidance.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages15

Reading Time38 min

AccessFree to download

Introduction

Droplet-based microfluidics and applications

Key factors influencing droplet size and regimes

Flow-focusing configurations and droplet behavior

Biotechnology Notes 6 (2025) 230–244 Contents lists available at ScienceDirect Biotechnology Notes journal [homepage:](homepage: www.keaipublishing.com/en/journals/biotechnology-notes/)[ www.keaipublishing.com/en/journals/biotechnology-notes/](homepage: www.keaipublishing.com/en/journals/biotechnology-notes/) | Research Article
CFD study and experimental verification of droplet formation characteristics in a flow-focusing microfluidic device | | | | | --- | --- | --- | --- | | Hajar Mohamadzade Sani , Seyed Mostafa Hosseinalipour *
CFD Lab and CAE Center, School of Mechanical Engineering, Iran University of Science & Technology, Tehran, Iran | | | | | A R T I C L E I N F O | | A B S T R A C T | | | Keywords:
Droplet-based microfluidics Droplet generation
Flow-focusing microchannel CFD simulation Multiphase flow
Level set method | | This study numerically investigates droplet formation in a three-dimensional flow-focusing microchannel and validates the results with a lithographically fabricated device (error < 4%). The effects of injection angle, continuous phase viscosity, flow velocities, and interfacial tension on two-phase flow regimes, instantaneous flow fields, droplet size, formation frequency, and breakup time were examined. At acute angles, increasing the injection angle delays droplet detachment, producing larger droplets with greater interdroplet distance. At obtuse angles, larger injection angles slow down droplet formation and produce smaller droplets with shorter spacing. The injection angle of θ = 90◦ yields the maximum droplet diameter. As the flow rate ratio increases, the influence of the injection angle decreases, whereas higher capillary numbers amplify its effect. Higher continuous phase viscosity and velocity accelerate droplet formation, producing smaller droplets, while higher dispersed phase velocity and interfacial tension delay detachment, yielding larger droplets. Repeatability tests (coefficient of variation < 1%) confirm high stability and reliability. These findings provide practical guidelines for designing controlled droplet generation in microfluidic applications. | | 1. Introduction Droplet-based microfluidics, which enables the precise manipulation of materials within microchannels as monodisperse droplets on the micrometer scale,1 has found widespread applications in chemistry,2 lab-on-a-chip technologies,3 clinical diagnostics, tissue engineering, pharmaceutical drug production and testing, nanoparticle synthesis,4 and emulsion formation.5–12 In recent years, this approach has gained significant attention due to its ability to generate uniform, micrometer-scale droplets on microfluidic chips, facilitating the handling of extremely small fluid volumes and enabling direct encapsulation of biological entities in various assays. Accurate control over droplet size, as well as uniform and integrated droplet production, is therefore critical in droplet-based microfluidics. Among the factors affecting droplet size, behavior, and droplet formation regimes are the droplet production channel geometry, the balance of interfacial tension forces between the two phases, and the properties of the continuous and dispersed phases.5,8,13–22 Surface effects are particularly important in microfluidic devices because the surface-to-volume ratio is high, and the interfacial tension must be sufficient to overcome shear stress.23,24 The geometry of the microfluidic device can also determine the fluid flow regime and the droplet shape. It has been shown that the geometry of the microfluidic platform at the two-phase interface strongly influences droplet shape.8,15 Commonly used microfluidic device geometries include cross-flow, co-flow, and flow-focusing configurations.16,25–28 Flow-focusing microfluidic devices are widely used to produce high-frequency, monodispersed, and uniform-sized droplets. For applications such as microparticle encapsulation, a flow-focusing microfluidi

FAQs

What is the main goal of this study?

To numerically investigate droplet formation in a 3D flow-focusing microchannel and validate the results experimentally using a fabricated device.

Which parameters are studied, and what outcomes do they influence?

Injection angle, continuous-phase viscosity, flow velocities, and interfacial tension are varied to assess flow regimes, droplet size, formation frequency, and breakup time.

How does injection angle affect droplet detachment and size?

At acute angles, increasing the injection angle delays detachment and produces larger droplets with greater interdroplet distance; at obtuse angles, larger angles slow formation and produce smaller droplets with shorter spacing.

Sep 29, 2026

Upload by Pentious