Spontaneous polarization and locomotion of an active particle with surface-mobile enzymes

TL;DR

This paper investigates how surface-mobile enzymes on active particles can spontaneously break symmetry and induce propulsion through a self-organized polarization mechanism driven by enzyme advection and phoretic flows.

Contribution

It introduces a novel mechanism where enzyme mobility and self-phoresis lead to spontaneous polarization and motility in active particles, including bifurcation analysis.

Findings

Spontaneous symmetry breaking leads to particle propulsion.

Enzyme advection by phoretic flows causes polarization.

Transition occurs via supercritical or subcritical bifurcations.

Abstract

We examine a mechanism of locomotion of active particles whose surface is uniformly coated with mobile enzymes. The enzymes catalyze a reaction that drives phoretic flows but their homogeneous distribution forbids locomotion by symmetry. We find that the ability of the enzymes to migrate over the surface combined with self-phoresis can lead to a spontaneous symmetry breaking instability whereby the homogeneous distribution of enzymes polarizes and the particle propels. The instability is driven by the advection of enzymes by the phoretic flows and occurs above a critical P\'eclet number. The transition to polarized motile states occurs via a supercritical or subcritical pitchfork bifurcations, the latter of which enables hysteresis and coexistence of uniform and polarized states.