# Driving dynamic colloidal assembly using eccentric self-propelled colloids

## TL;DR

This study uses simulations to demonstrate how eccentric self-propelled colloids can dynamically assemble passive colloids into dense clusters, revealing a novel demixing transition useful for designing responsive materials.

## Contribution

It introduces a new mechanism for dynamic colloidal assembly driven by eccentric active particles, including a re-entrant mixing behavior dependent on density.

## Key findings

- Eccentric active particles induce dense cluster formation of passive colloids.
- Dynamic demixing occurs when active particles move faster and overlap trajectories.
- Re-entrant mixing behavior observed at certain densities.

## Abstract

Designing protocols to dynamically direct the self-assembly of colloidal particles has become an important direction in soft matter physics because of the promising applications in fabrication of dynamic responsive functional materials. Here using computer simulations, we found that in the mixture of passive colloids and eccentric self-propelled active particles, when the eccentricity and self-propulsion of active particles are high enough, the eccentric active particles can push passive colloids to form a large dense dynamic cluster, and the system undergoes a novel dynamic demixing transition. Our simulations show that the dynamic demixing occurs when the eccentric active particles move much faster than the passive particles such that the dynamic trajectories of different active particles can overlap with each other while passive particles are depleted from the dynamic trajectories of active particles. Our results suggest that this is in analogy to the entropy driven demixing in colloid-polymer mixtures, in which polymer random coils can overlap with each other while deplete the colloids. More interestingly, we find that by fixing the passive colloid composition at certain value, with increasing the density, the system undergoes an intriguing re-entrant mixing, and the demixing only occurs within certain intermediate density range. This suggests a new way of designing active matter to drive the self-assembly of passive colloids and fabricate dynamic responsive materials.