Self-propelled worm-like filaments: spontaneous spiral formation, structure, and dynamics

Area of Science:

• Physics
• Soft Matter Physics
• Biophysics

Background:

• Filaments propelled along their tangent vector are common in biological and artificial systems.
• Understanding their dynamics and emergent structures is crucial for various applications.

Purpose of the Study:

• To investigate the behavior of 2D worm-like filaments under active propulsion using Brownian dynamics simulations.
• To explore the impact of propulsion strength and filament flexibility on dynamic and structural properties.

Main Methods:

• Brownian dynamics simulations in two dimensions.
• Exploration of a wide parameter space including propulsion strength and filament flexibility.
• Analysis of dynamic properties (mean square displacement, diffusion coefficients) and structural properties.

Main Results:

• Strongly propelled and flexible filaments spontaneously form stable spirals.
• Propulsion significantly affects dynamic properties like rotational and translational diffusion.
• An activity-induced contribution to the rotational diffusion coefficient was identified: v(c)/ξ(P).
• Structural properties remain largely unaffected by propulsion in the absence of spiral formation.

Conclusions:

• Active self-propulsion can lead to emergent collective behavior (spirals) in flexible filaments.
• The interplay between active propulsion and thermal fluctuations dictates the dynamic properties.
• The model provides insights into biological systems like microtubules and bacteria, as well as artificial microswimmers.