Visible-Light-Driven Hematite-Titania Janus Micromotors for Programmable Cargo Manipulation with Magnetically Triggered Release.

Programmable cargo manipulation is essential for microrobotic systems intended for targeted delivery, microscale assembly, and lab-on-a-chip applications. However, achieving autonomous cargo capture, guided transport, and on-demand release within a single light-driven platform remains challenging because cargo capture and release are often coupled to the same propulsion mechanism. Here, we report visible-light-driven hematite-titania (α-Fe2O3/TiO2) Janus micromotors that decouple cargo capture and cargo release through photocatalytically generated phoretic interactions and magnetic actuation. Under blue-light illumination, the micromotors exhibit autonomous propulsion with speeds up to 8.5 μm s-1 while operating at a low hydrogen peroxide concentration of only 0.5% (v/v). The micromotors enable repeated cargo pickup, transport, selective collection from mixed particle populations, and on-demand cargo release, while a single micromotor can simultaneously transport more than 15 silica microparticles. Importantly, magnetic-field-induced micromotor reorientation triggers cargo release without interrupting propulsion or altering the chemical environment. Numerical simulations support the proposed phoretic cargo-capture mechanism, while high-speed imaging and repeated release experiments provide complementary evidence for the magnetically triggered cargo-release strategy and its high repeatability. By independently controlling cargo capture and cargo release through complementary photocatalytic and magnetic mechanisms, this work establishes a versatile strategy for programmable microscale cargo manipulation.