2026/03/31 by Tachin Ruangkriengsin, Günther Turk, Howard A. Stone
Physics and Astronomy · #cond-mat.soft #physics.flu-dyn
paper · pdf · doi:10.1103/l316-fvkl
published as Physical Review Fluids 11 (6), 064103 (2026) · 19 pages, 5 figures
arxiv created 2026/08/05 · arxiv updated 2026/08/07
We study the self-diffusiophoresis of a spherical chemically active particle near a planar, impermeable wall, with a focus on the influence of particle orientation on propulsion. We analyze a Janus particle with asymmetric surface chemical activity, consisting of a small inert region within a catalytically active cap. While numerical simulations have been used to study such particles, they encounter difficulties resolving the flow and transport in the near-wall regime due to geometric confinement and steep solute concentration gradients. We address this limitation through an asymptotic analysis in the lubrication limit, where the gap between the particle and the wall is narrow. In particular, we consider the distinguished limit in which the inert region is asymptotically comparable in size to the lubrication region. We analyze an axisymmetric configuration in which the inert face is oriented parallel to the wall and extend the analysis to slightly tilted orientations. We find that the cap size determines whether a tilted particle rotates back toward the axisymmetric state or continues to reorient, thereby characterizing its rotational stability in the near-contact regime.