Facilitation of polymer looping and giant polymer diffusivity in crowded solutions of active particles

Shin, Jaeoh; Cherstvy, Andrey G.; Kim, Won Kyu; Metzler, Ralf

doi:10.1088/1367-2630/17/11/113008

Cited by 101 publications

(134 citation statements)

References 95 publications

(107 reference statements)

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“…Finally, upon increasing L f beyond the period of the fastest growing mode, the pressure imbalance folds the polymer. This instability thus partly explains the atypical folding of polymers in active baths reported numerically in the literature [26][27][28][29][30]. This transition as the size of the filament increases can be monitored in the diffusivity of its center of mass, which exhibits a sharp peak corresponding to self-propelled wedges (Fig.…”

Section: Fig 1c)mentioning

confidence: 68%

“…For flexible boundaries, we have shown how the fluctuations of the wall shape can be enhanced by pressure inhomogeneities which trigger a modulational instability. For freely moving objects and filaments, this instability sheds new light on a host of phenomena which have been observed numerically, such as the atypical looping and swelling of polymers in active baths [26][27][28][29][30] as well as predicts new behaviors.…”

Section: Fig 1c)mentioning

confidence: 99%

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Active Particles with Soft and Curved Walls: Equation of State, Ratchets, and Instabilities

et al. 2016

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We study, from first principles, the pressure exerted by an active fluid of spherical particles on general boundaries in two dimensions. We show that, despite the non-uniform pressure along curved walls, an equation of state is recovered upon a proper spatial averaging. This holds even in the presence of pairwise interactions between particles or when asymmetric walls induce ratchet currents, which are accompanied by spontaneous shear stresses on the walls. For flexible obstacles, the pressure inhomogeneities lead to a modulational instability as well as to the spontaneous motion of short semi-flexible filaments. Finally, we relate the force exerted on objects immersed in active baths to the particle flux they generate around them.Active forces have recently attracted much interest in many different contexts [1]. In biology, they play crucial roles on scales ranging from the microscopic, where they control cell shape and motion [2] to the macroscopic, where they play a dominant role in tissue dynamics [3,4]. More generally, active systems offer novel engineering perspectives, beyond those of equilibrium systems. In particular, boundaries have been shown to be efficient tools for manipulating active particles. Examples range from rectification of bacterial densities [5,6] and optimal delivery of passive cargoes [7] to powering of microscopic gears [8,9]. Further progress, however, requires a predictive theoretical framework which is currently lacking for active systems. To this end, simple settings have been at the core of recent active matter research.Understanding the effect of boundaries on active matter starts with the mechanical pressure exerted by an active fluid on its containing vessel. This question has been recently studied extensively for dry systems [10][11][12][13][14][15][16][17], revealing a surprisingly complex physics. For generic active fluids, the mechanical pressure is not a state variable [13]. The lack of equation of state, through a dependence on the wall details, questions the role of the mechanical pressure in any possible thermodynamic description of active systems [18,19]; it also leads to a richer phenomenology than in passive systems by allowing more general mechanical interplays between fluids and their containers.Interestingly, for the canonical model of self-propelled spheres of constant propelling forces, on which neither walls nor other particles exert torques, the pressure acting on a solid flat wall has been shown to admit an equation of state [11,12,19]. While the physics of this model does not clearly differ from other active systems, showing for instance wall accumulation [20] and motility-induced phase separation [21][22][23], the mechanical pressure exerted on a flat wall satisfies an equation of state, even in the presence of pairwise interactions [11,12,19]. One might thus hope that the intuition built on the rheology of equilibrium fluids extends to this case. Derived in a particular setting, the robustness of this equation of state however remains an open question. For...

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Section: Fig 1c)mentioning

confidence: 68%

Section: Fig 1c)mentioning

confidence: 99%

Active Particles with Soft and Curved Walls: Equation of State, Ratchets, and Instabilities

et al. 2016

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“…On the one hand, our polymer can be considered as comprised of active monomers, e.g., active Brownian particles [21,22,35,36,38,40]. On the other hand, the active force may originate from interactions with uncorrelated surrounding ABPs, hence, the polymer corresponds to a passive polymer dissolved in an active bath [30,41,42]. Examples for the latter can be found in biological system.…”

Section: Introductionmentioning

confidence: 99%

Conformational and dynamical properties of semiflexible polymers in the presence of active noise

Eisenstecken

Ghavami

Mair

et al. 2017

AIP Conference Proceedings

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Abstract. In the presence of active noise, flexible and semiflexible polymers exhibit drastically different conformational and dynamical features compared to the case of thermal (white) noise only. For a non-Markovian exponentially correlated temporal noise (colored noise), flexible polymers swell with increasing noise strength, whereas semiflexible polymers shrink first and, for larger noise strengths, swell similar to flexible polymers. Thereby, a suitable treatment of the finite polymer contour length is essential. The finite contour length implies a strong dependence of the polymer relaxation times on the noise strengths. We discuss the conformational and dynamical aspects in terms of an analytical model, adopting the continuous Gaussian semiflexible polymer description. Moreover, results of computer simulations are shown and compared with analytical results.

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“…A variant of our model also currently under investigation are "active colloidal polymers" [107,108,[123][124][125]. In this case, many colloidal particles are linked to a linear chain.…”

Section: Discussionmentioning

confidence: 99%

“…Two cases are analyzed in this context. On the one hand, the chain can be made of passive colloidal particles placed into a background of self-propelling microswimmers [123][124][125]. On the other hand, the chain itself could be composed of self-propelling Janus particles [107,108].…”

Section: Discussionmentioning

confidence: 99%

Getting drowned in a swirl: Deformable bead-spring model microswimmers in external flow fields

2016

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Deformability is a central feature of many types of microswimmers, e.g. for artificially generated self-propelled droplets. Here, we analyze deformable bead-spring microswimmers in an externally imposed solvent flow field as simple theoretical model systems. We focus on their behavior in a circular swirl flow in two spatial dimensions. Linear (straight) two-bead swimmers are found to circle around the swirl with a slight drift to the outside with increasing activity. In contrast to that, we observe for triangular three-bead or square-like four-bead swimmers a tendency of being drawn into the swirl and finally getting drowned, although a radial inward component is absent in the flow field. During one cycle around the swirl, the self-propulsion direction of an active triangular or square-like swimmer remains almost constant, while their orbits become deformed exhibiting an "egg-like" shape. Over time, the swirl flow induces slight net rotations of these swimmer types, which leads to net rotations of the egg-shaped orbits. Interestingly, in certain cases, the orbital rotation changes sense when the swimmer approaches the flow singularity. Our predictions can be verified in real-space experiments on artificial microswimmers.

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Facilitation of polymer looping and giant polymer diffusivity in crowded solutions of active particles

Cited by 101 publications

References 95 publications

Active Particles with Soft and Curved Walls: Equation of State, Ratchets, and Instabilities

Active Particles with Soft and Curved Walls: Equation of State, Ratchets, and Instabilities

Conformational and dynamical properties of semiflexible polymers in the presence of active noise

Getting drowned in a swirl: Deformable bead-spring model microswimmers in external flow fields

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