Wall-Induced Symmetry Breaking and Directional Stability in Single-Component Light-Driven Micromotors

Area of Science:

• Materials Science
• Chemical Engineering
• Physics

Background:

• Existing light-driven micromotors often require complex designs (material asymmetry, multicomponent) and external fields for control.
• These limitations complicate fabrication and restrict autonomous operation in nonequilibrium systems.

Purpose of the Study:

• To introduce a novel class of single-component, cube-shaped hematite (α-Fe2O3) micromotors.
• To demonstrate their autonomous propulsion and exceptional directional stability under visible light.
• To provide a theoretical framework explaining their unique motion characteristics.

Main Methods:

• Scalable, single-step hydrothermal synthesis of uniform α-Fe2O3 cubes.
• Observation of micromotor propulsion in dilute aqueous hydrogen peroxide under visible-light illumination.
• Theoretical modeling incorporating chemiosmotic slip and hydrodynamic interactions.

Main Results:

• Hematite cubes exhibit efficient self-propulsion, even at ultralow fuel concentrations (0.01% v/v).
• Micromotors maintain persistent, highly linear trajectories over extended distances without external alignment.
• Theoretical model validates spontaneous symmetry breaking and stable sliding states.

Conclusions:

• Cube-shaped hematite micromotors represent a minimal, intrinsically stable active colloid system.
• Geometry-controlled propulsion near solid surfaces is demonstrated, offering new insights.
• These micromotors provide a robust platform for studying active matter with high directional fidelity.