Effects of direction reversals on patterns of active filaments

Abbaspour, Leila; Malek, A.; Karpitschka, Stefan; Klumpp, Stefan

doi:10.48550/arxiv.2112.09188

Cited by 3 publications

(3 citation statements)

References 42 publications

(73 reference statements)

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“…This includes nutrient distribution [16,35,36], which leads to gradients of activity and thereby represents another opportunity for the passive properties of the system to become important, but also extends to structure formation in three dimensions [20,35,36], interactions with other types of activity such as motility and chemical signal production [37] and different kinds of confinement [38]. In addition, it may prove rewarding to look for even more general physical principles by exploring the similarities the system exhibits to dense systems of active polymers and filaments [39,40] due to its columnar structure.…”

Section: Discussionmentioning

confidence: 99%

Stress anisotropy in confined populations of growing rods

Isensee¹,

Hupe²,

Golestanian³

et al. 2022

Preprint

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Order and alignment are ubiquitous in growing colonies of rod-shaped bacteria due to the nematic properties of the constituent particles. These effects are the result of the active stresses generated by growth, passive mechanical interactions between cells, and flow-induced effects due to the shape of the confining container. However, how these contributing factors interact to give rise to the observed global alignment patterns remains elusive. Here, we study, in-silico, colonies of growing rod-shaped particles of different aspect ratios confined in channel-like geometries. A spatially resolved analysis of the stress tensor reveals a strong relationship between near-perfect alignment and an inversion of stress anisotropy for particles with large length-to-width ratios. We show that, in quantitative agreement with an asymptotic theory, strong alignment can lead to a decoupling of active and passive stresses parallel and perpendicular to the direction of growth, respectively. We demonstrate the robustness of these effects in a geometry that provides less restrictive confinement and introduces natural perturbations in alignment. Our results illustrate the complexity arising from the inherent coupling between nematic order and active stresses in growing active matter which is modulated by geometric and configurational constraints due to confinement.

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Section: Discussionmentioning

confidence: 99%

Stress anisotropy in confined populations of growing rods

Isensee¹,

Hupe²,

Golestanian³

et al. 2022

Preprint

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“…The former corresponds to persistent directional self-propulsion, while the latter is the result of fast and highly frequent motion reversals. In dilute systems, polar filaments exhibit spiralling and clustering that is activity and flexibility dependent 41 , while nematic filaments display a reduction in clustering and spiral formation as shown by a recent study comparing polar and nematic filaments at low density 43 . Polar filaments, at high densities, show a jamming transition that is activity dependent, while for densely packed nematic filaments 41 , the flexibility itself has been shown to be dependent on the activity, both in simulation 42 and experiments 44 .…”

Section: Introductionmentioning

confidence: 88%

Distinct impacts of polar and nematic self-propulsion on active unjamming

Venkatesh¹,

Mondal²,

Doostmohammadi³

2022

Preprint

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Though jamming transitions are long studied in condensed matter physics and granular systems, much less is known about active jamming (or unjamming), which commonly takes place in living materials. In this paper, we explore, by molecular dynamic simulations, the jamming-unjamming transition in a dense system of active semi-flexible filaments. In particular we characterise the distinct impact of polar versus nematic driving for different filament rigidity and at varying density. Our results show that high densities of dynamic active filaments can be achieved by only changing the nature of the active force, nematic or polar. Interestingly, while polar driving is more effective at unjamming the system at high densities below confluency, we find that at even higher densities nematic driving enhances unjamming compared to its polar counterpart. The effect of varying the rigidity of filaments is also significantly different in the two cases: while for nematic driving lowering bending rigidity unjams the system, we find an intriguing re-entrant jamming-unjamming-jamming transition for polar driving as the filament rigidity is lowered. While the first transition (unjamming) is driven by softening due to reduced rigidity, the second transition (jamming) is a cooperative effect of ordering and coincides with the emergence of nematic order in the system. Together, through a generic model of self-propelled flexible filaments, our results demonstrate how tuning the nature of self-propulsion and flexibility can be employed by active materials to achieve high densities without getting jammed.

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“…In addition, we induce single-particle reversals (SPR) as a stochastic switching modelled by a Poisson process, where the probability of reversal in a time window ∆t is p rev = e −γ∆t γ∆t, with rate parameter γ. Active matter systems with instantaneous Poissonian reversals have gained more attention in recent times both for interacting and non-interacting cases [38][39][40][41]. Such abrupt reversals are also observed in Nature, for example in some species of bacteria, including P. Putida and M. Xanthus [42,43].…”

mentioning

confidence: 99%

Collective states of active matter with stochastic reversals: emergent chiral states and spontaneous current switching

Olsen¹,

Angheluta²,

Flekkøy³

2022

Preprint

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We study collective dynamical behavior of active particles with topological interactions and directional reversals. Surprising phenomena are shown to emerge as the interaction relaxation time is varied relative to the reversal rate, such as spontaneous formation of collective chiral states due to phase synchronization, and collective directional reversals in the presence of confinement. The results have a direct relevance to modelling and understanding collective reversals and synchronization phenomena in active matter.

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Effects of direction reversals on patterns of active filaments

Cited by 3 publications

References 42 publications

Stress anisotropy in confined populations of growing rods

Stress anisotropy in confined populations of growing rods

Distinct impacts of polar and nematic self-propulsion on active unjamming

Collective states of active matter with stochastic reversals: emergent chiral states and spontaneous current switching

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