Active responsive colloids driven by intrinsic dichotomous noise

TL;DR

This paper investigates how intrinsic dichotomous noise influences the structure and dynamics of responsive colloids, revealing noise-driven phase transitions and altered diffusion in dense suspensions, with implications for designing adaptive active materials.

Contribution

It introduces a novel model of active responsive colloids driven by dichotomous noise, demonstrating how internal noise controls collective behavior and structural transitions.

Findings

Size distribution transitions from unimodal to bimodal with increasing density

Intrinsic noise significantly alters self-diffusion properties

Crowding effects influence spatial arrangements and relaxation times

Abstract

We study the influence of intrinsic noise on the structure and dynamics of responsive colloids (RCs) which actively change their size and mutual interactions. The colloidal size is explicitly resolved in our RC model as an internal degree of freedom (DOF) in addition to the particle translation. A Hertzian pair potential between the RCs leads to repulsion and shrinking of the particles, resulting in an explicit responsiveness of the system to self-crowding. To render the colloids active, their size is internally driven by a dichotomous noise, randomly switching ('breathing') between growing and shrinking states with a predefined rate, as motivated by recent experiments on synthetic active colloids. The polydispersity of this dichotomous active responsive colloid (D-ARC) model can be tuned by the parameters of the noise. Utilizing stochastic computer simulations, we study crowding effects on the spatial distributions, relaxation times, and self-diffusion of dense suspensions of the D-ARCs. We find a substantial influence of the 'built-in' intrinsic noise on the system's behavior, in particular, transitions from unimodal to bimodal size distributions for an increasing colloid density as well as intrinsic noise-modified diffusive translational dynamics. We conclude that controlling the noise of internal DOFs of a macromolecule or cell is a powerful tool for active colloidal materials to enable autonomous changes in the system's collective structure and dynamics towards the adaption of macroscopic properties to external perturbations.