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Quantifying active diffusion in an agitated fluid

Title data

Gires, Pierre-Yves ; Thampi, Mithun ; Weiss, Matthias:
Quantifying active diffusion in an agitated fluid.
In: Physical Chemistry Chemical Physics. Vol. 22 (11 September 2020) Issue 38 . - pp. 21678-21684.
ISSN 1463-9084
DOI: https://doi.org/10.1039/D0CP03629C

Abstract in another language

Mixing of reactants in microdroplets predominantly relies on diffusional motion due to small Reynolds numbers and the resulting absence of turbulent flows. Enhancing diffusion in microdroplets by an auxiliary noise source is therefore a topical problem. Here we report on how the diffusional motion of tracer beads is enhanced upon agitating the surrounding aqueous fluid with miniaturized magnetic stir bars that are compatible with microdroplets and microfluidic devices. Using single-particle tracking, we demonstrate via a broad palette of measures that local stirring of the fluid at different frequencies leads to an enhanced but apparently normal and homogenous diffusion process, i.e. diffusional steps follow the anticipated Gaussian distribution and no ballistic motion is observed whereas diffusion coefficients are significantly increased. The signature of stirring is, however, visible in the power-spectral density and in the velocity autocorrelation function of trajectories. Our data therefore demonstrate that diffusive mixing can be locally enhanced with miniaturized stir bars while only moderately affecting the ambient noise properties. The latter may also facilitate the controlled addition of nonequilibrium noise to complex fluids in future applications.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Chair Experimental Physics I - Physics of Living Matter > Chair Experimental Physics I - Physics of Living Matter - Univ.-Prof. Dr. Matthias Weiss
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 530 Physics
500 Science > 570 Life sciences, biology
Date Deposited: 23 Feb 2021 12:52
Last Modified: 23 Feb 2021 12:52
URI: https://eref.uni-bayreuth.de/id/eprint/63350