Micro-nanoarchitectonics of heterogeneous windmill-shaped microrobots with magneto-photothermal synergy for...

Microrobots capable of controlled propulsion and on-demand mass transport are vital for microscale engineering applications. Achieving a design that combines effective actuation, stable movement, and controllable cargo release in a single structure remains difficult. Herein, we report a rigid-soft hybrid microrobot fabricated via DLP 3D printing, featuring rigid blades embedded with aligned Fe₃O₄ particle chains to enhance magnetic torque for locomotion and a soft polydopamine (PDA)-doped hydrogel core for near-infrared (NIR)-responsive cargo delivery. Importantly, this architecture spatially decouples the propulsion and cargo-release functions, addressing the typical trade-offs between structural stiffness and photothermal efficiency observed in conventional monolithic mixtures. Kinematic analysis identifies the four-blade configuration as optimal, balancing velocity with directional linearity to overcome instability. Particle image velocimetry (PIV) and computational fluid dynamics reveal that the robot's rotation functions as a centrifugal pump, generating shear strain fields that disaggregate drug clusters. Furthermore, the coupling of magnetic active mixing and NIR-photothermal desorption yields a synergistic release mechanism, with about 85% cumulative release and approximately 93% mixing homogeneity in the field of view. This work establishes a structural design framework for stable active microdevices and elucidates the hydrodynamic mechanisms driving synergistic mass transport.