Directional Symmetry Breaking of Spherical Active Colloids by Magnetoviscous Coupling
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arXiv
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| Autores principales: | , , , , , , , |
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| Formato: | Preprint |
| Publicado: |
2026
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| _version_ | 1866910257802903552 |
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| author | Zhou, Ziyang Kobayashi, Takuya Saito, Keita Ito, Masato Yoshinaga, Kohei Iwashita, Yasutaka Beppu, Kazusa Maeda, Yusuke T. |
| author_facet | Zhou, Ziyang Kobayashi, Takuya Saito, Keita Ito, Masato Yoshinaga, Kohei Iwashita, Yasutaka Beppu, Kazusa Maeda, Yusuke T. |
| contents | Harnessing active matter requires strategies that break the directional symmetry of self-propelled motion without altering the propulsion mechanism itself. Here, we show that magnetically inert spherical active colloids can be steered through the anisotropic viscous response of a ferrofluid under a uniform magnetic field. Self-propelled Janus colloids exhibit robust cross-field motion transverse to the magnetic field, although the applied magnetic field directly controls neither the particles nor their propulsion speed. Quantitative measurements reveal an emergent reorientation torque that grows with propulsion speed and magnetic field strength. A squirmer model in a magnetoviscous medium captures these observations and shows that the torque arises from the coupling between swimmer-generated flow and anisotropic rotational viscosity. Our findings establish a hydrodynamic foundation for converting viscous dissipation into directional symmetry breaking through anisotropic rheology, providing a route to field-controlled material transport by active matter. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_26458 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Directional Symmetry Breaking of Spherical Active Colloids by Magnetoviscous Coupling Zhou, Ziyang Kobayashi, Takuya Saito, Keita Ito, Masato Yoshinaga, Kohei Iwashita, Yasutaka Beppu, Kazusa Maeda, Yusuke T. Soft Condensed Matter Harnessing active matter requires strategies that break the directional symmetry of self-propelled motion without altering the propulsion mechanism itself. Here, we show that magnetically inert spherical active colloids can be steered through the anisotropic viscous response of a ferrofluid under a uniform magnetic field. Self-propelled Janus colloids exhibit robust cross-field motion transverse to the magnetic field, although the applied magnetic field directly controls neither the particles nor their propulsion speed. Quantitative measurements reveal an emergent reorientation torque that grows with propulsion speed and magnetic field strength. A squirmer model in a magnetoviscous medium captures these observations and shows that the torque arises from the coupling between swimmer-generated flow and anisotropic rotational viscosity. Our findings establish a hydrodynamic foundation for converting viscous dissipation into directional symmetry breaking through anisotropic rheology, providing a route to field-controlled material transport by active matter. |
| title | Directional Symmetry Breaking of Spherical Active Colloids by Magnetoviscous Coupling |
| topic | Soft Condensed Matter |
| url | https://arxiv.org/abs/2605.26458 |