Dynamical self-assembly of dipolar active Brownian particles in two dimensions

Abstract

<p>The interplay between self-propulsion, steric repulsion, and dipolar interactions leads to a variety of collective states, including chains, clusters, and flocking patterns.</p>

Simulations of structure formation by confined dipolar active particles

“…This finding is in agreement with the recent results of Liao et al, who showed that the probability of chain formation is increased because of smaller mean separation between the particles for higher densities. 24 This explanation is confirmed by the observed shift of the critical magnetic strength with increasing density (Fig. 16b).…”

“…6 are qualitatively similar to bigger systems of dipolar active swimmers without confinement. 24 Importantly, by distinguishing the structured state more carefully (i.e. chains and rings) we can show that by changing the self-propulsion speed while keeping the magnetic strength constant one can influence the configuration of the dipolar swimmers.…”

“…To answer that question, we identified particle clusters using a density based cluster algorithm (DBSCAN 50 ), where the closest neighbor distance was set to e = 1.21s and the minimal number of particles in a neighborhood to form a cluster was set to N = 3 which is similar to other studies. 24,51 The value of e was determined by analysing the nearest neighbor distance g 1 (r), for m = 1 (see Fig. 2).…”

“…Self-assembly of dipolar passive particles in small systems 21 and in large systems has been studied theoretically, [22][23][24] partly motivated by observations in ferrofluids. [25][26][27] Small passive systems are known to form chains (N r 3), rings (3 o N r 17) or more complex, concentric multi-shell hexagonal patterns (N Z 18) as energetically favorable configurations in two dimensions.…”

“…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. However, the motion of active microswimmers is often confined either by their natural environment like interfacial barriers or by complex experimental setups like microfluidic devices.…”