Geometry-Controlled, Magnetically Guided Light-Driven Micromotors via Capillary-Assisted Particle Assembly

The geometry and surface functionality of micromotors critically influence their propulsion behavior, manoeuvrability, and application potential. However, scalable fabrication strategies that enable deterministic shape control together with multifunctional surface integration remain limited. Here, we present a modular platform for fabricating shape- and size-controlled, light-activated micromotors using Capillary-Assisted Particle Assembly (CAPA). Commercially available silica microparticles serve as building blocks and are assembled into predefined geometries within lithographically patterned templates through meniscus-driven capillary trapping. Subsequent thin-film deposition of titanium, nickel, and titania imparts structural integrity, magnetic responsiveness, and photocatalytic activity, respectively, yielding magnetically steerable, light-driven micromotors. Using this strategy, we fabricate linear-shaped micromotors of different sizes, as well as L- and tripod-shaped micromotors that exhibit active propulsion in an aqueous hydrogen peroxide medium under UV illumination, with average speeds of ~3-5 µm s^-1. The micromotors can be guided along predefined trajectories and further demonstrate selective cargo capture, transport, and release, enabling controlled in-plane manipulation. By combining particle assembly-based deterministic geometric design approach with functional material coatings, this approach provides a simple and versatile method for fabricating customized micromotor systems tailored for applications in microfluidics, lab-on-a-chip, and active-matter systems.