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arXiv · 2508.05643

Rolling at right angles: magnetic anisotropy enables dual-anisotropic active matter

Eavan Fitzgerald·Cécile Clavaud·Debasish Das·Isaac C. D. Lenton·Scott R. Waitukaitis
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Abstract

We report on an experimental active matter system with motion restricted to four cardinal directions. Our particles are magnetite-doped colloidal spheres driven by the Quincke electrorotational instability. The absence of a magnetic field (|B| = 0) leads to circular trajectories interspersed with short spontaneous runs. Intermediate fields (|B| < 20 mT) linearize the motion along the axis perpendicular to B. At high magnetic fields, we observe the surprising emergence of a second, distinct linearization along the axis parallel to B. With numerical simulations, we show that this behavior can be explained by anisotropic magnetic susceptibility

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Eavan Fitzgerald, Cécile Clavaud, Debasish Das, Isaac C. D. Lenton, Scott R. Waitukaitis. 2025-07-24. Rolling at right angles: magnetic anisotropy enables dual-anisotropic active matter. https://doi.org/10.1103/1ss8-31rb

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