Non-equilibrium dynamics of disordered bead-spring networks with active forces

Area of Science:

• Soft Matter Physics
• Complex Systems
• Materials Science

Background:

• Understanding the dynamics of active matter is crucial for designing novel materials.
• Bead-spring network models are widely used to study polymer and material properties.

Purpose of the Study:

• To investigate the Rouse-type dynamics of active harmonic bead-spring percolation clusters.
• To analyze the effects of different active stochastic forces (monopoles and dipoles) on network behavior.
• To explore the influence of these forces on network stability, swelling, shrinkage, and collapse transitions.

Main Methods:

• Langevin dynamics simulations were employed to model the system.
• Two types of active forces were considered: force monopoles and force dipoles, modeled as a random telegraph process.
• The study examined square and triangular lattice structures, including diluted regimes above the isostatic threshold.

Main Results:

• Force monopoles lead to a dynamically swollen network with sub-diffusive mean square displacement (MSD) behavior.
• Force dipoles cause network shrinkage and require long times to reach steady state, with MSD saturating and followed by ballistic/diffusive behaviors.
• In diluted regimes, dipoles induce 'rotational swimming'; triangular lattices show discontinuous collapse, while square lattices exhibit a continuous crossover to collapse.

Conclusions:

• Active force type critically determines network dynamics and stability.
• Disordered solids above the isostatic point are suggested to be stable against active dipolar forces under specific conditions.
• Lattice structure and dilution significantly influence response to active forces, impacting potential collapse transitions.