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Fission and fusion scenarios for magnetic microswimmer clusters

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ABSTRACT

Fission and fusion processes of particle clusters occur in many areas of physics and chemistry from subnuclear to astronomic length scales. Here we study fission and fusion of magnetic microswimmer clusters as governed by their hydrodynamic and dipolar interactions. Rich scenarios are found that depend crucially on whether the swimmer is a pusher or a puller. In particular a linear magnetic chain of pullers is stable while a pusher chain shows a cascade of fission (or disassembly) processes as the self-propulsion velocity is increased. Contrarily, magnetic ring clusters show fission for any type of swimmer. Moreover, we find a plethora of possible fusion (or assembly) scenarios if a single swimmer collides with a ringlike cluster and two rings spontaneously collide. Our predictions are obtained by computer simulations and verifiable in experiments on active colloidal Janus particles and magnetotactic bacteria.

No MeSH data available.


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Spontaneous fusion and fission for ring-like clusters with opposite vorticity.(b) Emerging states for all swimmer types as a function of reduced self-propulsion velocities v/v0—see Supplementary Movies 7–9. Each state is depicted in a sketch in panel a and can characterized by: (i) a non-rotating but translating coupled dimer, (ii) a counter rotating microswimmer chain orbiting around a ring of N=8 swimmers (iii) toddling and rotation, where the former rings exchange swimmers and translate, (iv) an emerging ring containing all N=10 swimmers as well as (v) collision induced and (vi) spontaneous fission of the ring-like clusters.
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f10: Spontaneous fusion and fission for ring-like clusters with opposite vorticity.(b) Emerging states for all swimmer types as a function of reduced self-propulsion velocities v/v0—see Supplementary Movies 7–9. Each state is depicted in a sketch in panel a and can characterized by: (i) a non-rotating but translating coupled dimer, (ii) a counter rotating microswimmer chain orbiting around a ring of N=8 swimmers (iii) toddling and rotation, where the former rings exchange swimmers and translate, (iv) an emerging ring containing all N=10 swimmers as well as (v) collision induced and (vi) spontaneous fission of the ring-like clusters.

Mentions: For pushers in the regime 0≤v/v0≤0.2, we observed an emerging coupled dimer, see Fig. 10 (Supplementary Movie 7). Here the two rings are coupled and translate together on a linear path in the absence of any global rotation. For larger velocities, 0.2<v/v0<0.3 the rings can exchange particles and moves with a complex combination of toddling and rotation (Supplementary Movie 8). Neutrals swimmers exhibit the same two states, coupled dimer for v/v0 ≤ 0.33 and the toddling and rotation state for 0.33<v/v0≤0.5. In addition to that the fusion into one ring containing all particles is possible for 0.5<v/v0≤0.67. Below the critical velocity for the spontaneous fission of an individual ring, the neutral swimmers exhibit some collision induced fission into various fragments of different size and shape. In contrast to pushers and neutral swimmers, the collision of two ring-like clusters of pullers show the fusion into a single ring and the induced fission as well show a new conformation. The new state, 0<v/v0≤0.5, shows a ring of N=8 pushers and a chain of two swimmers orbiting around the ring against its direction of rotation (Supplementary Movie 9).


Fission and fusion scenarios for magnetic microswimmer clusters
Spontaneous fusion and fission for ring-like clusters with opposite vorticity.(b) Emerging states for all swimmer types as a function of reduced self-propulsion velocities v/v0—see Supplementary Movies 7–9. Each state is depicted in a sketch in panel a and can characterized by: (i) a non-rotating but translating coupled dimer, (ii) a counter rotating microswimmer chain orbiting around a ring of N=8 swimmers (iii) toddling and rotation, where the former rings exchange swimmers and translate, (iv) an emerging ring containing all N=10 swimmers as well as (v) collision induced and (vi) spontaneous fission of the ring-like clusters.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121419&req=5

f10: Spontaneous fusion and fission for ring-like clusters with opposite vorticity.(b) Emerging states for all swimmer types as a function of reduced self-propulsion velocities v/v0—see Supplementary Movies 7–9. Each state is depicted in a sketch in panel a and can characterized by: (i) a non-rotating but translating coupled dimer, (ii) a counter rotating microswimmer chain orbiting around a ring of N=8 swimmers (iii) toddling and rotation, where the former rings exchange swimmers and translate, (iv) an emerging ring containing all N=10 swimmers as well as (v) collision induced and (vi) spontaneous fission of the ring-like clusters.
Mentions: For pushers in the regime 0≤v/v0≤0.2, we observed an emerging coupled dimer, see Fig. 10 (Supplementary Movie 7). Here the two rings are coupled and translate together on a linear path in the absence of any global rotation. For larger velocities, 0.2<v/v0<0.3 the rings can exchange particles and moves with a complex combination of toddling and rotation (Supplementary Movie 8). Neutrals swimmers exhibit the same two states, coupled dimer for v/v0 ≤ 0.33 and the toddling and rotation state for 0.33<v/v0≤0.5. In addition to that the fusion into one ring containing all particles is possible for 0.5<v/v0≤0.67. Below the critical velocity for the spontaneous fission of an individual ring, the neutral swimmers exhibit some collision induced fission into various fragments of different size and shape. In contrast to pushers and neutral swimmers, the collision of two ring-like clusters of pullers show the fusion into a single ring and the induced fission as well show a new conformation. The new state, 0<v/v0≤0.5, shows a ring of N=8 pushers and a chain of two swimmers orbiting around the ring against its direction of rotation (Supplementary Movie 9).

View Article: PubMed Central - PubMed

ABSTRACT

Fission and fusion processes of particle clusters occur in many areas of physics and chemistry from subnuclear to astronomic length scales. Here we study fission and fusion of magnetic microswimmer clusters as governed by their hydrodynamic and dipolar interactions. Rich scenarios are found that depend crucially on whether the swimmer is a pusher or a puller. In particular a linear magnetic chain of pullers is stable while a pusher chain shows a cascade of fission (or disassembly) processes as the self-propulsion velocity is increased. Contrarily, magnetic ring clusters show fission for any type of swimmer. Moreover, we find a plethora of possible fusion (or assembly) scenarios if a single swimmer collides with a ringlike cluster and two rings spontaneously collide. Our predictions are obtained by computer simulations and verifiable in experiments on active colloidal Janus particles and magnetotactic bacteria.

No MeSH data available.


Related in: MedlinePlus