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THIS SEMINAR WAS ORGANIZED BY NORDITA SOFT MATTER zoom link for this seminar :
https://stockholmuniversity.zoom.us/j/155379036
Recent microfluidic experiments on tail-swimming bacteria as well as on
fore-swimming planktonic algae have shown that these microscopic swimmers display interesting migration patterns when subject to a plane Poiseuille flow. Depending on the flow rate, the relatively rounder swimmers exhibit
trapping either in the high-shear region near the channel boundaries or in
the low-shear region in the vicinity of the channel centreline. The
elongated swimmers, however, appear to only exhibit high-shear trapping
over a range of flow rates. Motivated by these experiments, in this talk, I
will be presenting some of our recent efforts to understand the
shear-induced migration of a suspension of microswimmers subject to a
pressure-driven channel flow. We use theory and Langevin simulations to
analyse the interplay between the swimmers intrinsic stochastic motion, its
geometry and the imposed flow, in causing these migration patterns. On the
theoretical front, our effort relies on the use of the method of
multiple-time scale analysis to develop a drift-diffusion equation for the
cross-stream swimmer concentration profile. I will be showing how our
analysis enables us to conveniently organize the high- and low-shear
trapping profiles on a parameters space characterizing the swimmer geometry
and the flow strength, and compare these predictions to the experiments.
Finally, I will conclude with a note on the relevance of our work in using
flow to sort swimmers of different swimming mechanisms and geometries.