Dynamics of self-propelled tracer particles inside a polymer network

Area of Science:

• Physics
• Materials Science
• Biophysics

Background:

• Transport of particles through mesh-like structures like hydrogels and polymer matrices is common in nature.
• Both passive (colloids) and active (self-propelled) tracers are relevant in biological and synthetic systems.
• Computer simulations offer a powerful tool to study complex particle dynamics in confined environments.

Purpose of the Study:

• To investigate the dynamics of self-propelled tracer particles within a simulated polymer network.
• To elucidate the influence of tracer size, self-propulsion, and polymer network stiffness on particle motion.
• To analyze mean-squared displacement and van-Hove correlations to understand transport mechanisms.

Main Methods:

• Construction of a polymer network model on a diamond lattice.
• Utilization of computer simulations to model tracer particle dynamics.
• Calculation of time-averaged mean-squared displacement (MSD) and van-Hove correlations.

Main Results:

• Larger tracers experience caging effects, leading to subdiffusion, while smaller or highly active tracers exhibit superdiffusion due to easier cage escape.
• Increased network stiffness slows down tracer dynamics.
• Non-Gaussian behavior is more pronounced in active tracers at intermediate times.
• Long-time dynamics transition to diffusive for passive tracers but remain distinct for highly active ones.

Conclusions:

• Self-propulsion significantly alters tracer dynamics in polymer networks, deviating from passive transport.
• Tracer size and network properties critically determine the diffusion regime (subdiffusion vs. superdiffusion).
• The findings provide insights into particle transport mechanisms in complex biological and synthetic materials.