Anisotropy-Stabilized Propulsion and Cycloidal Cargo Transport in Driven Magnetic Platelets.

Abstract

Geometric and magnetic anisotropies provide a powerful and often overlooked way to control the dynamics of field-driven active colloids, enabling directional alignment, actuation, and transport. Here, we show that thin hematite platelets exhibit multiaxial propulsion and cycloidal trajectories when driven near a surface by a conically precessing magnetic field. By balancing magnetic, viscous and gravitational torques, we explain the different dynamic states, the transition between them and the emergent orientational switching of the platelet during motion. We demonstrate that the transport modes and their stability arise from the interplay between the particle shape, the permanent magnetization and the magnetic susceptibility anisotropy. When mixed with passive, microscopic cargoes, these anisotropy-stabilized dynamic modes enable different hydrodynamic trapping regimes inaccessible to isotropic rotors.