Relating rheotaxis and hydrodynamic actuation using asymmetric gold-platinum phoretic rods

Quentin Brosseau, Florencio Balboa Usabiaga, Enkeleida Lushi, Yang Wu, Leif Ristroph, Jun Zhang, Michael Ward, Michael J. Shelley

Research output: Contribution to journalArticlepeer-review

Abstract

We explore the behavior of micron-scale autophoretic Janus (Au/Pt) rods, having various Au/Pt 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 Au/Pt 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.

Original languageEnglish (US)
Article number178004
JournalPhysical Review Letters
Volume123
Issue number17
DOIs
StatePublished - Oct 25 2019

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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