) micromotors that exhibit autonomous propulsion with exceptional directional stability under visible-light illumination. The micromotors are synthesized by using a scalable, single-step hydrothermal method, yielding uniform cubes in large quantities. Under visible-light illumination in dilute aqueous hydrogen peroxide, the hematite cubes self-propel efficiently, achieving measurable speeds even at ultralow fuel concentrations (0.01% (v/v)). Strikingly, once activated, the micromotors maintain persistent, nearly perfectly linear trajectories over extended distances and times despite the absence of intrinsic material asymmetric or external alignment fields. We rationalize these observations using a theoretical framework that incorporates chemiosmotic slip at the underlying planar surface and hydrodynamic interactions. The model demonstrates that wall-induced spontaneous symmetry breaking can generate a stable sliding state with an enhanced orientational persistence. Together, these results establish cube-shaped hematite micromotors as a minimal and intrinsically stable active colloid system, offering new insights into geometry-controlled propulsion near a solid surface and providing a robust platform for studying active matter with high directional fidelity.
Kumar et al. (Wed,) studied this question.