Issue 11, 2021

Phase separation of an active colloidal suspension via quorum-sensing

Abstract

We present the Brownian dynamics simulation of an active colloidal suspension in two dimensions, where the self-propulsion speed of a colloid is regulated according to the local density sensed by it. The role of concentration-dependent motility in the phase-separation of colloids and their dynamics is investigated in detail. Interestingly, the system phase separates at a very low packing fraction (Φ ≈ 0.125) at higher self-propulsion speeds (Pe), into a dense phase coexisting with a homogeneous phase and attains a long-range crystalline order beyond the transition point. The transition point is quantified here from the local density profiles and local and global-bond order parameters. We have shown that the characteristics of the phase diagram are qualitatively akin to the active Brownian particle (ABP) model. Moreover, our investigation reveals that the density-dependent motility amplifies the slow-down of the directed speed, which facilitates phase-separation even at low packing fractions. The effective diffusivity shows a crossover from quadratic rise to a power-law behavior of exponent 3/2 with Pe in the phase-separated regime. Furthermore, we have shown that the effective diffusion decreases exponentially with packing fraction in the phase-separated regime, while it shows a linear decrease in the single phase regime.

Graphical abstract: Phase separation of an active colloidal suspension via quorum-sensing

Supplementary files

Article information

Article type
Paper
Submitted
01 Dec 2020
Accepted
27 Jan 2021
First published
28 Jan 2021

Soft Matter, 2021,17, 3153-3161

Phase separation of an active colloidal suspension via quorum-sensing

F. Jose, S. K. Anand and S. P. Singh, Soft Matter, 2021, 17, 3153 DOI: 10.1039/D0SM02131H

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