Dynamics of a linear magnetic “microswimmer molecule”

Babel, Sonja; Löwen, Hartmut; Menzel, Andreas M.

doi:10.1209/0295-5075/113/58003

Cited by 29 publications

(36 citation statements)

References 54 publications

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“…This definition is not completely sharp. Previously the attractive bond has been postulated to be permanent (like a springlike force) [25,26] but we generalize it here a bit towards other strong bonding attraction energies much larger than the thermal energy k B T . Typically the bonding force is then larger than or comparable to forces arising from selfpropulsion.…”

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confidence: 77%

“…Typically the bonding force is then larger than or comparable to forces arising from selfpropulsion. In this context we define an active molecules not as a single swimmer but as an assembly of many swimmers [25]. Many bead models for a single swimmer as the traditional three-bead Najafi-Golestanian swimmer [27] with nonreciprocal dynamics in the relative motion of the beads are in this sense not an active molecule.…”

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confidence: 99%

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Active colloidal molecules

Löwen¹

2018

EPL

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Like ordinary molecules are composed of atoms, colloidal molecules consist of several species of colloidal particles tightly bound together. If one of these components is self-propelled or swimming, novel "active colloidal molecules" emerge. Active colloidal molecules exist on various levels such as "homonuclear", "heteronuclear" and "polymeric" and possess a dynamical function moving as propellers, spinners or rotors. Self-assembly of such active complexes has been studied a lot recently and this perspective article summarizes recent progress and gives an outlook to future developments in the rapidly expanding field of active colloidal molecules. EPL perspective article invited by G. Muga

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confidence: 77%

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confidence: 99%

Active colloidal molecules

Löwen¹

2018

EPL

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“…The parameters in all cases are μ A =0.5 and α A =1.5 except for k=9, where μ A =0. 25. For all chains, by decreasing μ A the amplitude and frequency of oscillation grow and in the case of the k=9 chain a secondary oscillation is produced, possibly due to a secondary Hopfbifurcation.…”

Section: Chains With a Cargo: Flagellum-like Motionmentioning

confidence: 89%

“…In our case it comes from the phoretic interaction that breaks the action-reaction symmetry, but it could emerge in other systems with non-equilibrium interactions. A nice example of such oscillatory behavior is the magnetic chain studied in [25], which also included hydrodynamic interactions.…”

Section: Discussionmentioning

confidence: 99%

Active colloidal chains with cilia- and flagella-like motion

González

Soto

2018

New J. Phys.

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It has been shown that self-assembled chains of active colloidal particles can present sustained oscillations. These oscillations are possible because the effective diffusiophoretic forces that mediate the interactions of colloids do not respect the action-reaction principle and hence, a Hopfbifurcation is possible even for overdamped dynamics. Anchoring the particles in one extreme breaks the headtail symmetry and the oscillation is transformed into a traveling wave pattern, and thus the chain behaves like a beating cilium. The net force on the anchor, estimated using the resistive force theory, vanishes before the bifurcation and thereafter grows linearly with the bifurcation parameter. If the mobilities of the particles on one extreme are reduced to mimic an elongated cargo, the traveling wave generates a net velocity on the chain that now behaves like a moving flagellum. The average velocity again grows linearly with the bifurcation parameter. Our results demonstrate that simplified systems, consisting only of a few particles with non-reciprocal interaction and head-tail asymmetry, show beating motion and self-propulsion. Both properties are present in many non-equilibrium models thus making our results a general feature of active matter.

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“…Additionally, interesting phenomena can appear when hydrodynamic effects interplay with, e.g., magnetic interactions. 64,95 Generally, supplementing experiments and many-body particle-based simulations with statistical descriptions, e.g., density-field equations, allows for thorough theoretical analysis. Ideally, the observed phenomena are explained in this way and new types of behavior are predicted, leading to a better understanding of the underlying physical effects.…”

Section: Introductionmentioning

confidence: 99%

Multi-species dynamical density functional theory for microswimmers: Derivation, orientational ordering, trapping potentials, and shear cells

Hoell

Löwen

Menzel

2019

The Journal of Chemical Physics

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Microswimmers typically operate in complex environments. In biological systems, often diverse species are simultaneously present and interact with each other. Here, we derive a (time-dependent) particle-scale statistical description, namely a dynamical density functional theory, for such multi-species systems, extending existing works on one-component microswimmer suspensions. In particular, our theory incorporates the effect of external potentials, but also steric and hydrodynamic interactions between swimmers. For the latter, a previously introduced force-dipole-based minimal (pusher or puller) microswimmer model is used. As a limiting case of our theory, mixtures of hydrodynamically interacting active and passive particles are captured as well. After deriving the theory, we apply it to different planar swimmer configurations. First, these are binary pusher-puller mixtures in external traps. In the considered situations, we find that the majority species imposes its behavior on the minority species. Second, for unconfined binary pusher-puller mixtures, the linear stability of an orientationally disordered state against the emergence of global polar orientational order (and thus emergent collective motion) is tested analytically. Our statistical approach predicts, qualitatively in line with previous particle-based computer simulations, a threshold for the fraction of pullers and for their propulsion strength that lets overall collective motion arise. Third, we let driven passive colloidal particles form the boundaries of a shear cell, with confined active microswimmers on their inside. Driving the passive particles then effectively imposes shear flows, which persistently acts on the inside microswimmers. Their resulting behavior reminds of the one of circle swimmers, though with varying swimming radii. arXiv:1904.07277v2 [cond-mat.soft]

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Dynamics of a linear magnetic “microswimmer molecule”

Cited by 29 publications

References 54 publications

Active colloidal molecules

Active colloidal molecules

Active colloidal chains with cilia- and flagella-like motion

Multi-species dynamical density functional theory for microswimmers: Derivation, orientational ordering, trapping potentials, and shear cells

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