How walls affect the dynamics of self-phoretic microswimmers

• Published in: The European physical journal. ST, Special topics Special topics, 2016-10, Vol.225 (8-9), p.1843-1874
• Main Authors: Ibrahim, Y., Liverpool, T.B.
• Format: Article
• Language: English
• Subjects: Asymmetry; Atomic; Classical and Continuum Physics; Concentration gradient; Condensed Matter Physics; Materials Science; Measurement Science and Instrumentation; Modern Simulation Approaches in Soft Matter Science: From Fundamental Understanding to Industrial Applications; Molecular; Optical and Plasma Physics; Phase diagrams; Physics; Physics and Astronomy; Potential gradient; Regular Article
• ISSN: 1951-6355; 1951-6401
• DOI: 10.1140/epjst/e2016-60148-1

We study the effect of a nearby planar wall on the propulsion of a spherical phoretic micro-swimmer driven by reactions on its surface. An asymmetric coverage of catalysts on its surface which absorb reactants and generate products gives rise to an anisotropic interfacial flow that propels the swimmer. We analyse the near-wall dynamics of such a self-phoretic swimmer as a function of the asymmetric catalytic coverage of the surface. By an analysis of the fundamental singularities of the flow and concentration or electrostatic potential gradients generated we are able to obtain and rationalise a phase diagram of behaviours as a function of the characteristics of the swimmer surface. We find a variety of possible behaviours, from “bound states” where the swimmer remains near the wall to “scattering” or repulsive trajectories in which the swimmer ends far from the wall. The formation of some of the bound states is a purely wall-phoretic effect and cannot be obtained by simply mapping a phoretic swimmer to a hydrodynamic one.