Shape-dependent guidance of active Janus particles by chemically patterned surfaces

Abstract

Self-phoretic Janus particles move by inducing -- via non-equilibrium chemical reactions occurring on their surfaces -- changes in the chemical composition of the solution in which they are immersed. This process leads to gradients in chemical composition along the surface of the particle, as well as along any nearby boundaries, including solid walls. Chemical gradients along a wall can give rise to chemi-osmosis, i.e., the gradients drive surface flows which, in turn, drive flow in the volume of the solution. This bulk flow couples back to the particle, and thus contributes to its self-motility. Since chemi-osmosis strongly depends on the molecular interactions between the diffusing molecular species and the wall, the response flow induced and experienced by a particle encodes information about any chemical patterning of the wall. Here, we extend previous studies on self-phoresis of a sphere near a chemically patterned wall to the case of particles with elongated shape. We focus our analysis on the new phenomenology potentially emerging from the coupling -- which is inoperative for a spherical shape -- of the elongated particle to the strain rate tensor of the chemi-osmotic flow. Via numerical calculations, we show that the dynamics of a rod-like particle exhibits a novel "edge-following" steady state: the particle translates along the edge of a chemical step at a steady distance from the step and with a steady orientation. Within a certain range of system parameters, the edge-following state co-exists with a "docking" state (the particle stops at the step, oriented perpendicular to the step edge), i.e., a bistable dynamics occurs. These findings are rationalized as a consequence of the competition between fluid vorticity and the rate of strain by using analytical theory based on the point-particle approximation which captures quasi-quantitatively the dynamics of the system.

References in corpus (19)

• Active Particles in Complex and Crowded Environments
• Self-motile colloidal particles: from directed propulsion to random walk
• Propulsion of a molecular machine by asymmetric distribution of reaction--products
• Designing phoretic micro- and nano-swimmers
• Hydrodynamics of self-propulsion near a boundary: predictions and accuracy of far-field approximations
• Circular motion of asymmetric self-propelling particles
• Topographical pathways guide chemical microswimmers
• Phototaxis of synthetic microswimmers in optical landscapes
• Self-propulsion of a catalytically active particle near a planar wall: from reflection to sliding and hovering
• Gravitaxis of asymmetric self-propelled colloidal particles
• Electrokinetic Effects in Catalytic Pt-Insulator Janus Swimmers
• Artificial Rheotaxis
• Phoretic Motion of Spheroidal Particles Due To Self-Generated Solute Gradients
• Light-induced self-assembly of active rectification devices
• Rheotaxis of spherical active particles near a planar wall
• Guiding catalytically active particles with chemically patterned surfaces
• Active colloids in the context of chemical kinetics
• Taxis of Artificial Swimmers in a Spatio-Temporally Modulated Activation Medium
• Chemically active colloids near osmotic-responsive walls with surface-chemistry gradients

Cited by in corpus (7)

• Hydrodynamic Mobility Reversal of Squirmers near Flat and Curved Surfaces
• Activity-induced microswimmer interactions and cooperation in one-dimensional environments
• Optimal slip velocities of micro-swimmers with arbitrary axisymmetric shapes
• Diffusion-influenced reactions on non-spherical partially absorbing axisymmetric surfaces
• Diffusiophoretic propulsion of an isotropic active colloidal particle near a finite-sized disk embedded in a planar fluid-fluid interface
• Phase coexistence in a monolayer of active particles induced by Marangoni flows
• Onsager reciprocal relations and chemo-mechanical coupling for chemically-active colloids