Active Brownian particles and run-and-tumble particles separate inside a maze

Area of Science:

• Physics
• Statistical Mechanics
• Soft Matter Physics

Background:

• Active Brownian particles (ABPs) and run-and-tumble particles (RTPs) are key models for self-propelled matter.
• Understanding particle behavior in confined environments is crucial for controlling active matter systems.

Purpose of the Study:

• To investigate the separability of ABPs and RTPs using geometric confinement alone.
• To identify optimal maze geometries for particle separation.
• To develop a theoretical framework for predicting particle behavior in confined spaces.

Main Methods:

• Numerical simulations of non-interacting ABPs and RTPs in 2D maze geometries.
• Analysis of mean first-passage times and steady-state distributions.
• Development of a rate theory to model particle dynamics.

Main Results:

• Geometric confinement effectively separates ABPs from RTPs.
• Matryoshka-like mazes with circular shells exhibit the highest filtration efficiency.
• ABPs escape mazes faster, while RTPs navigate towards the center more readily.
• Simulations and rate theory show distinct spatial distributions for ABPs and RTPs in nested mazes.

Conclusions:

• Designing specific confining geometries offers a novel, label-free method for separating different types of self-propelled particles.
• Circular confinement is particularly effective for particle filtration.
• The developed rate theory accurately predicts particle behavior in complex geometries.