Vortex‐Assisted Fabrication of Magneto‐Optical Janus Microbeads and Their Magnetic Assembly

Magnetically integrated photonic microbeads have emerged as promising structural color pigments with controllable optical responses. Typical microfluidic approaches used to fabricate such advanced materials offer monodispersity and structural uniformity but remain limited in scalability. Here, we systematically investigate the direct coassembly of magnetite and monodisperse latex particles within aqueous emulsion droplets through a simple vortex‐assisted bulk emulsification approach. This scalable synthetic strategy yields stable magneto‐optical Janus microbeads comprising chemically cross‐linked ordered colloidal crystal compartments and disordered magnetic layers. The resulting magnetic microbeads exhibit tunable reflective structural colors across the visible spectrum. Moreover, their magnetic properties enable field‐responsive rotation, alignment, and directed assembly from viscous media into customized optical features. Such Janus microbeads demonstrate the potential of active structural color materials for magnetic field gradient assembly, enabling dynamic optical control for potential field‐responsive visualization and security technology.