Freeform optical flow based on meta-conveyors for compact, programmable in situ nanomanipulation

Programming light flow offers significant potential for diverse applications. However, conventional spatial light modulators are bulky, have large pixels, and slow switching. Miniaturized metasurface strategies offer flexibility but are limited to radial or azimuthal phase gradients, hindering free shaping of light flow in ultracompact footprints. Here, we present a meta-conveyor technique (MCT) using metasurfaces to encode user-defined optical flow, demonstrating programmable stable transport of nanoparticles (NPs) with arbitrary open-path round‑trip movement and on‑demand stopping. Theoretical analysis reveals efficient phase gradient switching from hybrid propagation and geometric phases, enabling tunable lateral optical forces via input and output polarization control. We validate universality with a maze‑solving meta‑conveyor that drives NPs from entrance to exit while avoiding dead ends. The MCT provides a compact, passive platform for programmable on‑chip manipulation, opening avenues for heterogeneously integrated clinical devices in minimally invasive and extreme environments.