Chemotactic behavior for a self-phoretic Janus particle near a patch source of fuel

TL;DR

This study investigates the chemotactic behavior of a self-phoretic Janus particle near a chemical patch, revealing conditions for stable hovering states influenced by fuel release and particle response.

Contribution

It introduces a detailed analysis of chemotaxis in Janus particles near chemical patches, highlighting the effects of fuel dynamics and phoretic mobility on particle behavior.

Findings

Particle can be attracted to a stable hovering state.

Hovering state depends on fuel release and consumption rates.

Particle aligns normal to the wall at a specific distance.

Abstract

Many biological microswimmers are capable of chemotaxis, i.e., they can sense an ambient chemical gradient and adjust their mechanism of motility to move towards or away from the source of the gradient. Synthetic active colloids endowed with chemotactic behavior hold considerable promise for targeted drug delivery and the realization of programmable and reconfigurable materials. Here we study the chemotactic behavior of a Janus particle, which converts ``fuel'' molecules, released at an axisymmetric chemical patch located on a planar wall, into ``product'' molecules at its catalytic cap and moves by self-phoresis induced by the product. The chemotactic behavior is characterized as a function of the interplay between the rates of release (at the patch) and the consumption (at the particle) of fuel, as well as of details of the phoretic response of the particle (i.e., its phoretic mobility). Among others, we find that, under certain conditions, the particle is attracted to a stable ``hovering state'' in which it aligns its axis normal to the wall and rests (positions itself) at an activity-dependent distance above the center of the patch.