Self-propulsion of a catalytically active particle near a planar wall: from reflection to sliding and hovering

TL;DR

This paper models the behavior of catalytically active Janus particles near a wall, predicting various motion states such as reflection, steady sliding, or hovering, based on particle design and interactions with solutes.

Contribution

It provides a theoretical framework for understanding and predicting the motion of active particles near boundaries, highlighting how surface chemistry influences their behavior.

Findings

Particles exhibit reflection, steady sliding, or hovering near walls.

Steady states depend on catalyst coverage and solute interactions.

Design parameters can be tuned to achieve desired motion behaviors.

Abstract

Micron-sized particles moving through solution in response to self-generated chemical gradients serve as model systems for studying active matter. Their far-reaching potential applications will require the particles to sense and respond to their local environment in a robust manner. The self-generated hydrodynamic and chemical fields, which induce particle motion, probe and are modified by that very environment, including confining boundaries. Focusing on a catalytically active Janus particle as a paradigmatic example, we predict that near a hard planar wall such a particle exhibits several scenarios of motion: reflection from the wall, motion at a steady-state orientation and height above the wall, or motionless, steady "hovering." Concerning the steady states, the height and the orientation are determined both by the proportion of catalyst coverage and the interactions of the solutes with the different "faces" of the particle. Accordingly, we propose that a desired behavior can be selected by tuning these parameters via a judicious design of the particle surface chemistry.