Complex Flow Dynamics at Microscale

Dear Colleagues,

Microfluidics deals with fluid flows confined in channels with a characteristic length scale of the order of hundreds of microns at most. Therefore, at microscale, most of the flows are intrinsically laminar, with low numerical values of Reynolds. This may wrongly be assumed to be synonymous to simple and predictable flow dynamics. Nevertheless, under severe confinement conditions, a wide variety of scientific problems emerge, leading to challenging problems that make this topic worthy of being the focus of this Special Issue. Among a plethora of very interesting problems, we would like to highlight the following ones:

Micromixing: At low Reynolds numbers, two streams of fluids will flow parallel to each other and will not mix, simply because laminar diffusion dominates the flow. This has led to extensive studies with different approaches (active and passive micromixers) aiming at increasing mixing efficiency.

Microrheometry: At small length scales, the elasticity number, which represents the balance between elastic and inertial forces, is intrinsically large for viscoelastic fluids. Thus, the microscale opens a new door for rheometric purposes, providing an excellent platform for characterizing complex fluids with a low relaxation time and low viscosity unreachable at macroscale. Moreover, at microscale, new flowfield configurations could be proposed for the rheological characterization of magneto and electrorheological fluids.

Flow around obstacles: The analysis of complex flow dynamics around microdevices with potential use in biomedicine is essential for the development of optimal microbots and biosensors to minimize their impact on the patient body and to improve the binding efficiency of analyte–ligand through a sensitive membrane, respectively. 

All these problems and many more, such as those topics related to elastic instabilities, particle migration, hemodynamics, and fluid–structure Interactions, require extensive fundamental study from all approaches, i.e., theoretical, numerical, and experimental. This Special Issue is expected to gather contributions that describe recent results obtained in complex flow dynamics at microscale and to demonstrate how those results could be important in terms of real-world application.

Dr. Francisco J. Galindo-Rosales
Dr. Laura Campo-Deaño
Guest Editors

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