Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Y20: Active Matter and Liquid Crystals in Biological and Bio-Inspired Systems IV
8:00 AM–10:36 AM,
Friday, March 18, 2022
Room: McCormick Place W-185BC
Sponsoring
Units:
DSOFT DPOLY GSNP
Chair: Antonio Tavera-Vázquez, Chicago
Abstract: Y20.00005 : Rheotaxis of active droplets*
8:48 AM–9:00 AM
Presenter:
Prateek Dwivedi
(Indian institute of technology Kanpur)
Authors:
Prateek Dwivedi
(Indian institute of technology Kanpur)
Rahul Mangal
(Indian institute of technology Kanpur)
Rheotaxis is a well-known phenomenon among microbial organisms and artificial active colloids, wherein the swimmers respond to an imposed flow. We report the first experimental evidence of upstream rheotaxis by spherical active droplets. It is shown that the presence of a nearby wall and the resulting strong flow-gradient at the droplet level is at the root of this phenomenon. Experiments with optical cells of different heights reveal that rheotaxis is observed only for a finite range of shear rates, independent of the bulk flow rate. We conjecture that the flow induced distortion of an otherwise isotropic distribution of filled/empty micelles around the droplet propels it against the flow. We also show that nematic droplets exhibit elastic stress-induced oscillations during their rheotactic flight. A promising potential of manipulating the rheotactic behavior to trap as well as shuttle droplets between target locations is demonstrated, paving way to potentially significant advancement in bio-medical applications.
*Indian Institute of Technology Kanpur
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