Motion of discoidal catalytic Janus particles near a planar wall

Catalytic Janus particles self-propel by decomposition of chemical “fuel” available in liquid solution. The resulting self-generated hydrodynamic and chemical fields extend into, and are modified by, the surrounding environment, coupling back to the motion of the particle. Previous experimental and theoretical work has shown that spherical Janus particles near a hard planar wall can exhibit surface-bound “sliding” and “hovering” states of motion. More recently, the effect of non-spherical particle shape has come into focus, driven by developments in particle fabrication. Here, we consider the dynamics of a discoidal Janus particle near a planar wall. Via numerical calculations, we find that changing the particle’s aspect ratio can qualitatively change the particle’s dynamical behavior, e.g., by inducing two co-existing fixed points for the height and orientation. Using far-field analytical expressions for the interaction between the particle and the wall, we show how these bifurcations emerge from the interplay of hydrodynamics, phoresis, and particle shape.