Aggregation dynamics of active rotating particles in dense passive media

Area of Science:

• Physics
• Soft Matter Physics
• Colloidal Science

Background:

• Active matter systems display emergent non-equilibrium behaviors driven by particle activity.
• Effective interactions in active systems lead to complex collective phenomena.
• Understanding particle dynamics in passive environments is crucial for active matter research.

Purpose of the Study:

• To investigate the aggregation and dynamical behavior of active rotating particles (spinners) in 2D passive colloidal monolayers.
• To determine the factors influencing spinner aggregation and attraction within the passive matrix.
• To explore the formation of clusters in ternary mixtures of passive particles and spinners.

Main Methods:

• Experimental observation of active spinners in colloidal monolayers.
• Computational simulations to model spinner-monolayer interactions.
• Analysis of aggregation dynamics and dependence on mechanical properties and activity levels.

Main Results:

• Spinner aggregation observed, resembling classical 2D Cahn-Hilliard coarsening.
• Aggregation requires an elastic passive monolayer and a minimum spinner activity threshold.
• Characteristic cluster size observed, optimizing aggregation by balancing drag and stress.
• Ternary mixtures show segregation into co-rotating and counter-rotating spinner clusters.

Conclusions:

• Active spinners exhibit collective aggregation in passive 2D environments under specific conditions.
• Mechanical properties of the surrounding medium and particle activity are key regulators of aggregation.
• The study reveals mechanisms for self-organization in active-disordered systems.