Active colloidal propulsion over a crystalline surface

Udit Choudhury, Arthur V. Straube, Peer Fischer, John G. Gibbs, Felix Höfling

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

We study both experimentally and theoretically the dynamics of chemically self-propelled Janus colloids moving atop a two-dimensional crystalline surface. The surface is a hexagonally close-packed monolayer of colloidal particles of the same size as the mobile one. The dynamics of the self-propelled colloid reflects the competition between hindered diffusion due to the periodic surface and enhanced diffusion due to active motion. Which contribution dominates depends on the propulsion strength, which can be systematically tuned by changing the concentration of a chemical fuel. The mean-square displacements (MSDs) obtained from the experiment exhibit enhanced diffusion at long lag times. Our experimental data are consistent with a Langevin model for the effectively two-dimensional translational motion of an active Brownian particle in a periodic potential, combining the confining effects of gravity and the crystalline surface with the free rotational diffusion of the colloid. Approximate analytical predictions are made for the MSD describing the crossover from free Brownian motion at short times to active diffusion at long times. The results are in semi-quantitative agreement with numerical results of a refined Langevin model that treats translational and rotational degrees of freedom on the same footing.

Original languageEnglish (US)
Article number125010
JournalNew Journal of Physics
Volume19
Issue number12
DOIs
StatePublished - Dec 2017
Externally publishedYes

Keywords

  • active Brownian particles
  • colloidal microswimmers
  • hexagonal close-packed monolayer
  • surface diffusion

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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