Viscous flow through microfabricated axisymmetric contraction/expansion geometries
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RESEARCH ARTICLE
Viscous flow through microfabricated axisymmetric contraction/ expansion geometries Francisco Pimenta1 · Kazumi Toda‑Peters2 · Amy Q. Shen2 · Manuel A. Alves1 · Simon J. Haward2 Received: 9 June 2020 / Revised: 5 August 2020 / Accepted: 14 August 2020 © The Author(s) 2020
Abstract We employ a state-of-the-art microfabrication technique (selective laser-induced etching) to fabricate a set of axisymmetric microfluidic geometries featuring a 4:1 contraction followed by a 1:4 downstream expansion in the radial dimension. Three devices are fabricated: the first has a sudden contraction followed by a sudden expansion, the second features hyperbolic contraction and expansion profiles, and the third has a numerically optimized contraction/expansion profile intended to provide a constant extensional/compressional rate along the axis. We use micro-particle image velocimetry to study the creeping flow of a Newtonian fluid through the three devices and we compare the obtained velocity profiles with finite-volume numerical predictions, with good agreement. This work demonstrates the capability of this new microfabrication technique for producing accurate non-planar microfluidic geometries with complex shapes and with sufficient clarity for optical probes. The axisymmetric microfluidic geometries examined have potential to be used for the study of the extensional properties and non-linear dynamics of viscoelastic flows, and to investigate the transport and deformation dynamics of bubbles, drops, cells, and fibers. Graphic abstract
* Simon J. Haward [email protected]
Manuel A. Alves [email protected]
Francisco Pimenta [email protected]
1
Departamento de Engenharia Química, CEFT, Faculdade de Engenharia da Universidade do Porto, 4200‑465 Porto, Portugal
2
Micro/Bio/Nanofluidics Unit, Okinawa Institute of Science and Technology, Onna‑son, Okinawa 904‑0495, Japan
Kazumi Toda‑Peters [email protected] Amy Q. Shen [email protected]
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1 Introduction Microfluidics involves fluid flows at small length scales, typically 𝓁 ∼ 100 μ m (Stone and Kim 2001). Over the last two decades, the fabrication of microfluidic devices has been dominated by soft lithography techniques, which enable precise fabrication of channels with a planar rectangular cross-section, with complex variations of the geometry only possible in two dimensions (2D) (McDonald and Whitesides 2002). However, in many cases, a 2D approximation of a problem of interest is not ideal and researchers would prefer, if possible, to retain the use of the third dimension in the design of their model microfluidic systems. A prime example is for the in vitro study of hemodynamics, which requires model blood vessels with a circular cross-section (Doutel et al. 2015; Kang et al. 2018). In addition, many processes of interest, for example spraying, inkjet printing, and fiber spinning, involve fluid flows through circular ducts and nozzles or spinnerets. In all these processes, fluid elements are subjecte
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