Spontaneous rotation can stabilise ordered chiral active fluids

Maitra, Ananyo; Lenz, Martin

doi:10.1038/s41467-019-08914-7

Cited by 32 publications

(17 citation statements)

References 46 publications

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“…Whereas it is not unlikely for such a feature to originate from statistical errors, here we demonstrate that chiral active stresses affect the dynamics of +1/2 defects precisely by rotating their direction of motion with respect to p. In fact, the angle between p and the direction of motion of the defects could be used to indirectly measure the relative magnitude of the chiral stress τ compared to the deviatoric stress α. This phenomenon shares some similarities with recent results by Maitra and Lenz about the dynamics of +1/2 disclinations in rotating active nematics [35].…”

Section: Defect Motionsupporting

confidence: 91%

Chiral stresses in nematic cell monolayers

et al. 2020

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Recent experiments on monolayers of spindle-like cells plated on adhesive stripe-shaped domains have provided a convincing demonstration that certain types of collective phenomena in epithelia are well described by active nematic hydrodynamics. While recovering some of the hallmark predictions of this framework, however, these experiments have also revealed a number of unexpected features that could be ascribed to the existence of chirality over length scales larger than the typical size of a cell. In this article we elaborate on the microscopic origin of chiral stresses in nematic cell monolayers and investigate how chirality affects the motion of topological defects, as well as the collective motion in stripe-shaped domains. We find that chirality introduces a characteristic asymmetry in the collective cellular flow, from which the ratio between chiral and non-chiral active stresses can be inferred by particle-image-velocimetry measurements. Furthermore, we find that chirality changes the nature of the spontaneous flow transition under confinement and that, for specific anchoring conditions, the latter has the structure of an imperfect pitchfork bifurcation. arXiv:1909.05856v1 [cond-mat.soft]

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Section: Defect Motionsupporting

confidence: 91%

Chiral stresses in nematic cell monolayers

et al. 2020

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“…Note that there is no dependence on density in (15) due to the assumption that the spins are on a lattice. This is therefore equivalent to the equation used for the velocity field in Malthusian Toner-Tu [40] albeit here realized not in a motile system but on a lattice-based system [41].…”

Section: Stability Analysismentioning

confidence: 99%

“…In the flocking models we consider, birds are individually achiral and carry only a position and a vectorial orientation. Thus, despite the possibility of drawing angular momentum from the ambient air, self-propelling activity does not lead to a net persistent rotational motion of an individual bird [15]. Transient chirality and, hence, spontaneous rotation can arise only through interaction between birds.…”

Section: Introductionmentioning

confidence: 99%

Nonmutual torques and the unimportance of motility for long-range order in two-dimensional flocks

et al. 2020

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As the constituent particles of a flock are polar and in a driven state, their interactions must, in general, be foreaft asymmetric and nonreciprocal. Within a model that explicitly retains the classical spin angular momentum field of the particles we show that the resulting asymmetric contribution to interparticle torques, if large enough, leads to a buckling instability of the flock. More precisely, this asymmetry also yields a natural mechanism for a difference between the speed of advection of polarization information along the flock and the speed of the flock itself, concretely establishing that the absence of detailed balance, and not merely the breaking of Galilean invariance, is crucial for this distinction. To highlight this we construct a model of asymmetrically interacting spins fixed to lattice points and demonstrate that the speed of advection of polarization remains nonzero. We delineate the conditions on parameters and wave number for the existence of the buckling instability. Our theory should be consequential for interpreting the behavior of real animal groups as well as experimental studies of artificial flocks composed of polar motile rods on substrates.

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“…Understanding the outcome of the interplay between chirality and activity is an important and timely question. In stark contrast with the case of achiral active nematics, which has commanded a lot of attention in recent years, much less is known about the dynamics of chiral active systems (17)(18)(19). Previous work has mainly focused on cases where chirality only enters the system because of activity in the form of a nonequilibrium torque dipole (17,18).…”

mentioning

confidence: 99%

“…In stark contrast with the case of achiral active nematics, which has commanded a lot of attention in recent years, much less is known about the dynamics of chiral active systems (17)(18)(19). Previous work has mainly focused on cases where chirality only enters the system because of activity in the form of a nonequilibrium torque dipole (17,18). Instead, we consider here a system that is inherently chiral and apolar and therefore, can be modeledin the passive phase-as a cholesteric liquid crystal (CLC) (20,21).…”

mentioning

confidence: 99%

Rotation and propulsion in 3D active chiral droplets

Carenza

Gonnella

Marenduzzo

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Chirality is a recurrent theme in the study of biological systems, in which active processes are driven by the internal conversion of chemical energy into work. Bacterial flagella, actomyosin filaments, and microtubule bundles are active systems that are also intrinsically chiral. Despite some exploratory attempt to capture the relations between chirality and motility, many features of intrinsically chiral systems still need to be explored and explained. To address this gap in knowledge, here we study the effects of internal active forces and torques on a 3-dimensional (3D) droplet of cholesteric liquid crystal (CLC) embedded in an isotropic liquid. We consider tangential anchoring of the liquid crystal director at the droplet surface. Contrary to what happens in nematics, where moderate extensile activity leads to droplet rotation, cholesteric active droplets exhibit more complex and variegated behaviors. We find that extensile force dipole activity stabilizes complex defect configurations, in which orbiting dynamics couples to thermodynamic chirality to propel screw-like droplet motion. Instead, dipolar torque activity may either tighten or unwind the cholesteric helix and if tuned, can power rotations with an oscillatory angular velocity of 0 mean.

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Spontaneous rotation can stabilise ordered chiral active fluids

Cited by 32 publications

References 46 publications

Chiral stresses in nematic cell monolayers

Chiral stresses in nematic cell monolayers

Nonmutual torques and the unimportance of motility for long-range order in two-dimensional flocks

Rotation and propulsion in 3D active chiral droplets

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