Mixing and demixing of binary mixtures of polar chiral active particles

Ai, Bao-quan; Shao, Zhi-Gang; Zhong, Wei

doi:10.1039/c8sm00444g

Cited by 49 publications

(30 citation statements)

References 44 publications

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“…As compared to the monochromatic case, less is known about the patterns emerging in (aligning) circle swimmers with different frequencies. For such mixtures, broadly occurring both in nature and in the world of synthetic microswimmers, previous work has focused on synchronization of circle swimmers 15 , reporting the formation of counterrotating macroclusters as a side result and similar structures discussed in 25 . Here, we explore and characterize pattern formation in chiral active mixtures more systematically and provide a state arXiv:1901.08496v1 [cond-mat.soft] 24 Jan 2019 diagram significantly extending the one in 15 .…”

Section: Introductionmentioning

confidence: 99%

Simultaneous phase separation and pattern formation in chiral active mixtures

Levis

Liebchen

2019

Phys. Rev. E

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Chiral active particles, or self-propelled circle swimmers, from sperm cells to asymmetric Janus colloids, form a rich set of patterns, which are different from those seen in linear swimmers. Such patterns have mainly been explored for identical circle swimmers, while real-world circle swimmers, typically possess a frequency distribution. Here we show that even the simplest mixture of (velocity-aligning) circle swimmers with two different frequencies, hosts a complex world of superstructures: The most remarkable example comprises a microflock pattern, formed in one species, while the other species phase separates and forms a macrocluster, coexisting with a gas phase. Here, one species microphaseseparates and selects a characteristic length scale, whereas the other one macrophase separates and selects a density. A second notable example, here occurring in an isotropic system, are patterns comprising two different characteristic length scales, which are controllable via frequency and swimming speed of the individual particles.

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Section: Introductionmentioning

confidence: 99%

Simultaneous phase separation and pattern formation in chiral active mixtures

Levis

Liebchen

2019

Phys. Rev. E

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“…Chiral active matter has been experimentally realized, for example, in bacteria 53 and artificial L-shaped particles 54 . The hydrodynamics 55,56 and the phase separation 57 of chiral active matter have also been analyzed in recent studies. The effective Hamiltonian of the linearized hydrodynamic equations in active matter is, in general, non-Hermitian because of inherent dissipations and energy injections therein.…”

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confidence: 99%

Exceptional non-Hermitian topological edge mode and its application to active matter

2020

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Topological materials exhibit edge-localized scattering-free modes protected by their nontrivial bulk topology through the bulk-edge correspondence in Hermitian systems. While topological phenomena have recently been much investigated in non-Hermitian systems with dissipations and injections, the fundamental principle of their edge modes has not fully been established. Here, we reveal that, in non-Hermitian systems, robust gapless edge modes can ubiquitously appear owing to a mechanism that is distinct from bulk topology, thus indicating the breakdown of the bulk-edge correspondence. The robustness of these edge modes originates from yet another topological structure accompanying the branchpoint singularity around an exceptional point, at which eigenvectors coalesce and the Hamiltonian becomes nondiagonalizable. Their characteristic complex eigenenergy spectra are applicable to realize lasing wave packets that propagate along the edge of the sample. We numerically confirm the emergence and the robustness of the proposed edge modes in the prototypical lattice models. Furthermore, we show that these edge modes appear in a model of chiral active matter based on the hydrodynamic description, demonstrating that active matter can exhibit an inherently non-Hermitian topological feature. The proposed general mechanism would serve as an alternative designing principle to realize scattering-free edge current in non-Hermitian devices, going beyond the existing frameworks of non-Hermitian topological phases.

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“…Mixing inside a microchannel can be done in two ways: passive or active, each of which has proposed different techniques [13][14][15]. Passive micromixers provide favorable crochannels is in the laminar flow range in most practical applications.…”

Section: Introductionmentioning

confidence: 99%

“…Mixing inside a microchannel can be done in two ways: passive or active, each o which has proposed different techniques [13][14][15]. Passive micromixers provide favorabl mixing only through their inherent structure and thus, have many advantages, such a low cost, ease of construction, and no need for moving parts or additional power [16,17] The fluid flow is forced to change direction, split, combine, or develop the contact surfac in such passive structures [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the Heterogeneity Effect on Electroosmotic Micromixers Based on the Standard Deviation of Concentration and Mixing Entropy Index

et al. 2021

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One approach to achieve a homogeneous mixture in microfluidic systems in the quickest time and shortest possible length is to employ electroosmotic flow characteristics with heterogeneous surface properties. Mixing using electroosmotic flow inside microchannels with homogeneous walls is done primarily under the influence of molecular diffusion, which is not strong enough to mix the fluids thoroughly. However, surface chemistry technology can help create desired patterns on microchannel walls to generate significant rotational currents and improve mixing efficiency remarkably. This study analyzes the function of a heterogeneous zeta-potential patch located on a microchannel wall in creating mixing inside a microchannel affected by electroosmotic flow and determines the optimal length to achieve the desired mixing rate. The approximate Helmholtz–Smoluchowski model is suggested to reduce computational costs and simplify the solving process. The results show that the heterogeneity length and location of the zeta-potential patch affect the final mixing proficiency. It was also observed that the slip coefficient on the wall has a more significant effect than the Reynolds number change on improving the mixing efficiency of electroosmotic micromixers, benefiting the heterogeneous distribution of zeta-potential. In addition, using a channel with a heterogeneous zeta-potential patch covered by a slip surface did not lead to an adequate mixing in low Reynolds numbers. Therefore, a homogeneous channel without any heterogeneity would be a priority in such a range of Reynolds numbers. However, increasing the Reynolds number and the presence of a slip coefficient on the heterogeneous channel wall enhances the mixing efficiency relative to the homogeneous one. It should be noted, though, that increasing the slip coefficient will make the mixing efficiency decrease sharply in any situation, especially in high Reynolds numbers.

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Mixing and demixing of binary mixtures of polar chiral active particles

Cited by 49 publications

References 44 publications

Simultaneous phase separation and pattern formation in chiral active mixtures

Simultaneous phase separation and pattern formation in chiral active mixtures

Exceptional non-Hermitian topological edge mode and its application to active matter

Numerical Analysis of the Heterogeneity Effect on Electroosmotic Micromixers Based on the Standard Deviation of Concentration and Mixing Entropy Index

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