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ICS-3 Group Seminar:

Microfluidic flows and instabilities of complex fluids

Prof. Amy Shen

OIST (Okinawa Institute of Science and Technolgy), Japan

Anfang
30.04.2019 10:30 Uhr
Ende
30.04.2019 11:30 Uhr
Veranstaltungsort
Seminarraum A1-3, Building 04.6, Entrance E1

Abstract:

Microfluidics has emerged as a powerful platform of investigating flow instabilities at small lengh scales, as it provides access to regimes of low inertia and high elasticity and allows for the study of purely elastic flow instabilities and elastic turbulence, which occur at low Reynolds numbers but high Weissenberg numbers. In this talk, I will focus on an example of using cross-slot microfluidics to explore how fluid elasticity affects inertial flow instability: Simple fluids often display flow instabilities involving the production of vortices. However, studying how polymers and vortices interact is challenging because vortices generally fluctuate significantly and polymer effects at low concentrations can be subtle. A better understanding of these interactions is needed to optimize the use of polymer additives in industrial and biomedical applications ranging from lab-on-a-chip devices to large pipelines. We fabricated unique glass microfluidic devices containing junctions to make measurements on a single, steady, stationary vortex by direct visualization at high frame rates. By adding increasing amounts of a flexible polymer to water-based solvents, we discovered that the addition of the polymer is destabilizing and lowers the threshold flow rate needed for vortex formation. At the same time, we found that the polymer significantly reduces the strength of the resulting vortex. Our discoveries provide new insight regarding the competing effects of inertial and elastic instabilities on vortex formation and dynamics at small length scales [1,2]. If time permits, I will also show some ongoing work of flow around microfluidic cylinders using both polymer and wormlike micellar solutions [3-5].

  1. N. Burshtein, K. Zografos, A. Q. Shen, R. J. Poole, and S. J. Haward, Inertioelastic flow instability at a stagnation point, Physical Review X, 7, 041039-18, (2017).
  2. K. Zografos, N. Burshtein, A. Q. Shen, S. J. Haward, R. J. Poole, Elastic modifications of an inertial instability in a 3D cross-slot, Journal of Non-Newtonian Fluid Mechanics, 262, 12-14, (2018).
  3. S. J. Haward, K. Toda-Peters, A. Q. Shen, Steady viscoelastic flow around high-aspect-ratio, low-blockage-ratio microfluidic cylinders, Journal of Non-Newtonian Fluid Mechanics, 254, 23-35, (2018).
  4. N. Burshtein, S. Chan, K. Toda-Peters, A. Q. Shen, S. J. Haward, Microfluidic fabrication with selective laser-induced etching: New opportunities in fluid dynamics and rheology, Current Opinion in Colloid & Interface Science, (2018). https://doi.org/10.1016/j.cocis.2018.12.005
  5. S. J. Haward, N. Kitajima, K. Toda-Peters, T. Takahashi and A. Q. Shen, Flow of wormlike micellar solutions around microfluidic cylinders with high aspect ratio and low blockage ratio, Soft Matter, 2019, DOI: 10.1039/c8sm02099j

Kontakt

Dr. Kyongok Kang
Telefon: +49 2461 61-6089
Fax: +49 2461 61-2280
E-Mail: k.kang@fz-juelich.de

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