Abstract
Dipolar active particles describe a class of self-propelled, biological or artificial particles equipped with an internal (typically magnetic) dipole moment. Because of the interplay between self-propulsion and dipole-dipole interactions, complex collective behavior is expected to emerge in systems of such particles. Here, we use Brownian dynamics simulations to explore this collective behavior. We focus on the structures that form in small systems in spatial confinement. We quantify the type of structures that emerge and how they depend on the self-propulsion speed and the dipolar (magnetic) strength of the particles. We observe that the dipolar active particles self-assemble into chains and rings. The dominant configuration is quantified with an order parameter for chain and ring formation and shown to depend on the self-propulsion speed and the dipolar magnetic strength of the particles. In addition, we show that the structural configurations are also affected by the confining walls. To that end, we compare different confining geometries and study the impact of a reorienting 'wall torque' upon collisions of a particle with a wall. Our results indicate that dipolar interactions can further enhance the already rich variety of collective behaviors of active particles.
Highlights
Self-propelled active particles that convert energy from their environment into directed motion are known to exhibit rich collective behavior such as self-organized pattern formation or swarming due to an interplay between various interaction forces.[1,2,3] Microscopic active particles in fluids, so-called microswimmers, have been a particular focus of research both because of their rich dynamics[4] and because of their potential in biomedical applications.[5,6]From an application point of view, an important feature of active particles is their accessibility to remote control
A biological example of a dipolar microswimmer is given by magnetotactic bacteria.[7,8,9,10,11]
We solve the equations of motion in two dimensions by using overdamped Brownian dynamics (BD) simulations
Summary
Self-propelled active particles that convert energy from their environment into directed motion are known to exhibit rich collective behavior such as self-organized pattern formation or swarming due to an interplay between various interaction forces.[1,2,3] Microscopic active particles in fluids, so-called microswimmers, have been a particular focus of research both because of their rich dynamics[4] and because of their potential in biomedical applications.[5,6]. Guzman-Lastra et al have investigated the hydrodynamic flow fields of selfassembled microswimmers They studied how hydrodynamic and magnetic interactions affect cluster formation.[33] In another study by Liao et al the effect of motility and dipolar interactions on cluster formation has been investigated. In their Brownian dynamics simulations, they observed formation of chain-like structures and that motility-induced phase separation (MIPS) is generally suppressed by dipolar interactions.[24]. Most of these studies have focused on the collective behavior in spatially homogeneous environments. We ask what structures (such as chains and rings) emerge and how these structures are affected by motility and magnetic interactions as well as by the geometry of the confining chamber and by the interactions of the swimmer with the confining walls
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
