Autophoretic skating along permeable surfaces*

Janus particles are self-propelled colloidal locomotors that convert chemical energy into mechanical motion. Their asymmetric catalytic coating mediates chemical reactions in the surrounding fluid. The resulting solute concentration gradients drive slip flows along the particle surface, generating self-propulsion through diffusiophoresis. Via an interplay of chemical and hydrodynamic interactions, phoretic particles are known to swim along solid surfaces. In our analytical study we generalize this, investigating boundary guidance along a chemically permeable surface of two immiscible liquids, constituting a plausible model for autophoretic skating on biofilms or hydrogels. We also consider how particle-particle interactions affect the dynamics of multiple skaters. This opens exciting possibilities for applications in microfluidics and targeted drug delivery, where collective navigation through complex microscale environments is crucial.