Complex Fluid Flows in Microfluidics

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "C1: Micro/Nanoscale Electrokinetics".

Deadline for manuscript submissions: 31 May 2025 | Viewed by 1652

Special Issue Editor

Special Issue Information

Dear Colleagues,

This Special Issue is devoted to the intricate world of complex fluid flows in microfluidics, a domain that has revolutionized numerous scientific and engineering fields. Microfluidics, the science and technology of manipulating fluids at the micrometer scale, presents unique challenges and opportunities in understanding and controlling fluid behavior. Complex fluid flows, encompassing non-Newtonian fluids and multiphase flows, are critical to advancing applications in biotechnology, medicine, and chemical engineering. This Special Issue seeks to gather cutting-edge research that explores novel theoretical models, experimental techniques, and computational simulations in order to address the complexities of fluid dynamics in microfluidic systems.

We are delighted to invite you to contribute to our Special Issue on "Complex Fluid Flows in Microfluidics". It aims to showcase the latest research and innovations in understanding and manipulating complex fluid dynamics at the micrometer scale. We welcome original research articles and comprehensive reviews that explore theoretical, experimental, and computational aspects of microfluidic systems. Your contributions will help to elucidate the intricate behaviors of complex fluids and inspire new applications as well as technologies. We look forward to your participation and to sharing the remarkable advancements in microfluidics with the broader scientific community.

Dr. Célio Fernandes
Guest Editor

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Keywords

  • microfluidics
  • non-Newtonian fluids
  • multiphase flows
  • microfluidic device design
  • computational fluid dynamics
  • flow visualization
  • heat transfer in microfluidics

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Published Papers (2 papers)

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Research

21 pages, 5078 KiB  
Article
Experimental and Numerical Study of Slug-Flow Velocity Inside Microchannels Through In Situ Optical Monitoring
by Samuele Moscato, Emanuela Cutuli, Massimo Camarda and Maide Bucolo
Micromachines 2025, 16(5), 586; https://doi.org/10.3390/mi16050586 - 17 May 2025
Viewed by 93
Abstract
Miniaturization and reliable, real-time, non-invasive monitoring are essential for investigating microfluidic processes in Lab-on-a-Chip (LoC) systems. Progress in this field is driven by three complementary approaches: analytical modeling, computational fluid dynamics (CFD) simulations, and experimental validation techniques. In this study, we present an [...] Read more.
Miniaturization and reliable, real-time, non-invasive monitoring are essential for investigating microfluidic processes in Lab-on-a-Chip (LoC) systems. Progress in this field is driven by three complementary approaches: analytical modeling, computational fluid dynamics (CFD) simulations, and experimental validation techniques. In this study, we present an on-chip experimental method for estimating the slug-flow velocity in microchannels through in situ optical monitoring. Slug flow involving two immiscible fluids was investigated under both liquid–liquid and gas–liquid conditions via an extensive experimental campaign. The measured velocities were used to determine the slug length and key dimensionless parameters, including the Reynolds number and Capillary number. A comparison with analytical models and CFD simulations revealed significant discrepancies, particularly in gas–liquid flows. These differences are mainly attributed to factors such as gas compressibility, pressure fluctuations, the presence of a liquid film, and leakage flows, all of which substantially affect flow dynamics. Notably, the percentage error in liquid–liquid flows was lower than that in gas–liquid flows, largely due to the incompressibility assumption inherent in the model. The high-frequency monitoring capability of the proposed method enables in situ mapping of evolving multiphase structures, offering valuable insights into slug-flow dynamics and transient phenomena that are often difficult to capture using conventional measurement techniques. Full article
(This article belongs to the Special Issue Complex Fluid Flows in Microfluidics)
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10 pages, 1280 KiB  
Article
Flowing Liquid Crystal Torons Around Obstacles
by Júlio P. A. Santos, Mahmoud Sedahmed, Rodrigo C. V. Coelho and Margarida M. Telo da Gama
Micromachines 2024, 15(11), 1302; https://doi.org/10.3390/mi15111302 - 26 Oct 2024
Cited by 3 | Viewed by 1116
Abstract
Liquid crystal torons, localized topological structures, are known for their stability and dynamic behaviour in response to external stimuli, making them attractive for advanced material applications. In this study, we investigate the flow of torons in chiral nematic liquid crystals around obstacles. We [...] Read more.
Liquid crystal torons, localized topological structures, are known for their stability and dynamic behaviour in response to external stimuli, making them attractive for advanced material applications. In this study, we investigate the flow of torons in chiral nematic liquid crystals around obstacles. We simulate the fluid flow and director field interactions using a hybrid numerical method combining lattice Boltzmann and finite difference techniques. Our results reveal that the toron dynamical behaviour depends strongly on the impact parameter from the obstacle. At impact parameters smaller than half cholesteric pitch, the flowing toron is destabilized by the interaction with the obstacle; otherwise, the flowing toron follows a trajectory with a deflection which decays exponentially with the impact parameter. Additionally, we explore the scattering of torons by multiple obstacles, providing insights into how the dynamics of these structures respond to complex environments. Full article
(This article belongs to the Special Issue Complex Fluid Flows in Microfluidics)
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