Sorting of chiral microswimmers

Mijalkov, Mite; Volpe, Giovanni

doi:10.1039/c3sm27923e

Cited by 177 publications

(175 citation statements)

References 37 publications

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“…It was seen that SPP are capable of turning gears and produce net work on large objects [12][13][14][15], provided that there is an intrinsic asymmetry in such objects. Also, it is possible to separate SPP based on their rotational diffusion [16]. In addition to these phenomena, particle motion rectification was shown to occur when SPP are in the presence of funnel-shaped channels [6,8,[17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Self-propelled particle transport in regular arrays of rigid asymmetric obstacles

2014

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We report numerical results which show the achievement of net transport of self-propelled particles (SPP) in the presence of a two-dimensional regular array of convex, either symmetric or asymmetric, rigid obstacles. The repulsive inter-particle (soft disks) and particle-obstacle interactions present no alignment rule. We find that SPP present a vortex-type motion around convex symmetric obstacles even in the absence of hydrodynamic effects. Such a motion is not observed for a single SPP, but is a consequence of the collective motion of SPP around the obstacles. An steady particle current is spontaneously established in an array of non-symmetric convex obstacle (which presents no cavity in which particles may be trapped in), and in the absence of an external field. Our results are mainly a consequence of the tendency of the self-propelled particles to attach to solid surfaces.

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Section: Introductionmentioning

confidence: 99%

Self-propelled particle transport in regular arrays of rigid asymmetric obstacles

2014

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“…Consequently, shaken granular particles [5] and phoretically propelled colloidal particles [6-9] have been investigated in detail. Moreover, the observed collective behavior might find applications in, e.g., the sorting [10] and transport of cargo [11].Here we are interested in the phase behavior of repulsive particles below the freezing density. While in equilibrium only one fluid phase exists, sufficiently dense suspensions of repulsive self-propelled disks undergo an "active phase separation", i.e., particles aggregate into a dense, transiently ordered cluster surrounded by a dilute gas phase.…”

mentioning

confidence: 99%

“…Consequently, shaken granular particles [5] and phoretically propelled colloidal particles [6][7][8][9] have been investigated in detail. Moreover, the observed collective behavior might find applications in, e.g., the sorting [10] and transport of cargo [11].…”

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confidence: 99%

Effective Cahn-Hilliard Equation for the Phase Separation of Active Brownian Particles

et al. 2014

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The kinetic separation of repulsive active Brownian particles into a dense and a dilute phase is analyzed using a systematic coarse-graining strategy. We derive an effective Cahn-Hilliard equation on large length and time scales, which implies that the separation process can be mapped onto that of passive particles. A lower density threshold for clustering is found, and using our approach we demonstrate that clustering first proceeds via a hysteretic nucleation scenario and above a higher threshold changes into a spinodal-like instability. Our results are in agreement with particle-resolved computer simulations and can be verified in experiments of artificial or biological microswimmers.PACS numbers: 82.70. Dd,64.60.Cn The collective behavior of living "active" matter has recently attracted considerable interest from the statistical physics community (for reviews, see Refs. 1, 2). Even if the mutual interactions of the individual units are following simple rules, complex spatiotemporal patterns can emerge. Examples in nature occur on a wide range of scales from flocks of birds [3] to bacterial turbulence [4]. A basic physical model is obtained by describing the individual entities as particles with internal degrees of freedom (in the simplest case just an orientation) that consume energy and are thus driven out of thermal equilibrium. Consequently, shaken granular particles [5] and phoretically propelled colloidal particles [6-9] have been investigated in detail. Moreover, the observed collective behavior might find applications in, e.g., the sorting [10] and transport of cargo [11].Here we are interested in the phase behavior of repulsive particles below the freezing density. While in equilibrium only one fluid phase exists, sufficiently dense suspensions of repulsive self-propelled disks undergo an "active phase separation", i.e., particles aggregate into a dense, transiently ordered cluster surrounded by a dilute gas phase. This has been observed first [12,13] in computer simulations of a minimal model [14][15][16]. Clustering has also been reported in experiments using colloidal suspensions of active Brownian particles, in which the particles are phoretically propelled along their orientations due to the catalytic decomposition of hydrogen peroxide on a platinum hemisphere [7], or due to lightactivated hematite [8]. In these experiments, phoretic attractive forces play an important role. A closer realization of ideally repulsive particles is possible through the reversible local demixing of a near-critical water-lutidine mixture [17]. Colloidal particles propelled due to the ensuing local density gradients show indeed the predicted phase separation [9]. While in passive suspensions phaseseparation occurs only for sufficiently strong attractive forces, the microscopic mechanism for repulsive active particles is due to self-trapping: colliding particles block each other due to the persistence of their orientation [9]. In sufficiently dense suspensions, the "pressure" of the free, fast particles leads to the...

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“…A similar systematic reduction procedure in case of ABPs is nowadays still missing. Here, we fill this gap for the simple case of a micro-swimmer with constant speed as studied in [48][49][50][51][52][53][54][55][56][57][58][59] and in many other applications. We will proceed in a similar way as it is presented in Sec.…”

Section: Introductionmentioning

confidence: 99%

Eliminating inertia in a stochastic model of a micro-swimmer with constant speed

Milster

Nötel

Sokolov

et al. 2017

Eur. Phys. J. Spec. Top.

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We are concerned with the dynamical description of the motion of a stochastic micro-swimmer with constant speed and fluctuating orientation in the long time limit by adiabatic elimination of the orientational variable. Starting with the corresponding full set of Langevin equations, we eliminate the memory in the stochastic orientation and obtain a stochastic equation for the position alone in the overdamped limit. An equivalent procedure based on the Fokker-Planck equation is presented as well.

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Sorting of chiral microswimmers

Cited by 177 publications

References 37 publications

Self-propelled particle transport in regular arrays of rigid asymmetric obstacles

Self-propelled particle transport in regular arrays of rigid asymmetric obstacles

Effective Cahn-Hilliard Equation for the Phase Separation of Active Brownian Particles

Eliminating inertia in a stochastic model of a micro-swimmer with constant speed

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