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  • Open Access

Confinement-Induced Motion of Ciliates

G. C. Antunes*, C. Obst, and H. Stark

  • *Contact author: g.antunes@tu-berlin.de
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Phys. Rev. Lett. 137, 068301 – Published 3 August, 2026

DOI: https://doi.org/10.1103/c9nx-h2jk

Abstract

The time dynamics of flagellar and ciliary beating is often neglected in theories of microswimmers, with the most common models prescribing a time-constant actuation of the surrounding fluid. By explicitly introducing a metachronal wave, coarse-grained to a sinusoidal surface slip velocity, we show that a spatial resonance between the metachronal wave and the corrugation of a confining cylindrical channel enables a ciliate to swim even when it cannot move forward in a bulk fluid. Using lubrication theory, we reduce the problem to the Adler equation that reveals an oscillatory and steady swimming regime. Interestingly, a ciliate can even reverse its swimming direction in a corrugated channel compared to the bulk fluid.

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Phys. Rev. Lett. 137, 068301– Published 3 August, 2026
  • Received 21 January 2026
  • Accepted 1 July 2026
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