Simultaneous phase separation and pattern formation in chiral active mixtures

Abstract

Chiral active particles, or self-propelled circle swimmers, from sperm cells to asymmetric Janus colloids, form a rich set of patterns, which are different from those seen in linear swimmers. Such patterns have mainly been explored for identical circle swimmers, while real-world circle swimmers, typically possess a frequency distribution. Here we show that even the simplest mixture of (velocity-aligning) circle swimmers with two different frequencies, hosts a complex world of superstructures: The most remarkable example comprises a microflock pattern, formed in one species, while the other species phase separates and forms a macrocluster, coexisting with a gas phase. Here, one species microphaseseparates and selects a characteristic length scale, whereas the other one macrophase separates and selects a density. A second notable example, here occurring in an isotropic system, are patterns comprising two different characteristic length scales, which are controllable via frequency and swimming speed of the individual particles.

Reconfigurable emergent patterns in active chiral fluids

“…As evident from our data, the system of pear-shaped rollers exhibits a spontaneous chirality induced phase separation from initially random distribution of chiral rollers. Observed rotating flocks with spontaneous segregation of CW and CCW rotations are reminiscent of rotating droplet patterns realized in computational studies of Vicsek-like models for chiral swimmers with a circular motion [46][47][48] .…”

Spinning Rigid Bodies Driven by Orbital Forcing: The Role of Dry Friction

“…On each collision, a new RR could start. For chiral mixtures of bodies with distinct attributes [25], one expects a yet much richer behavior induced by "polydispersity", similarly to what occurs with the phase behavior of multicomponent fluids [26][27][28][29]. A fundamental setting would be a binary mixture of bodies that can undergo RRs with others that cannot.…”

Susceptibility of Orientationally-Ordered Active Matter to Chirality Disorder

“…While some of these works have revealed interesting phenomena, such as the non-reciprocal phase transitions of [35], others did consider the robustness of polar flocks and all concluded, often implicitly, that they resist a finite amount of disorder. This conclusion was in particular reached for systems with chirality disorder, in which selfpropelled particles each possess an intrinsic tendency to turn either clockwise (CW) or counterclockwise (CCW), but with the total population remaining globally achiral [30,31].…”

“…Is orientationally-ordered active matter equally susceptible to population disorder? Only a few active systems with heterogeneous population have been studied so far [25][26][27][28][29][30][31][32][33][34][35]. Again, most of these works deal with aligning self-propelled particles and investigate the fate of collective motion phases.…”