Abstract
We explore the behavior of micron-scale autophoretic Janus () rods, having various length ratios, swimming near a wall in an imposed background flow. We find that their ability to robustly orient and move upstream, i.e., to rheotax, depends strongly on the ratio, which is easily tunable in synthesis. Numerical simulations of swimming rods actuated by a surface slip show a similar rheotactic tunability when varying the location of the surface slip versus surface drag. The slip location determines whether swimmers are pushers (rear actuated), pullers (front actuated), or in between. Our simulations and modeling show that pullers rheotax most robustly due to their larger tilt angle to the wall, which makes them responsive to flow gradients. Thus, rheotactic response infers the nature of difficult to measure flow fields of an active particle, establishes its dependence on swimmer type, and shows how Janus rods can be tuned for flow responsiveness.
- Received 13 June 2019
- Revised 20 August 2019
DOI:https://doi.org/10.1103/PhysRevLett.123.178004
© 2019 American Physical Society
Physics Subject Headings (PhySH)
Focus
Asymmetry Helps Tiny Rods Swim Upstream
Published 25 October 2019
Changing the length ratio of the two segments of a microswimmer affects its ability to automatically swim against the current.
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