Long-range optical pulling enabled by longitudinal chirality gradients

Long-range optical pulling is highly desired for nanoscale manipulation, including biomolecules and functional particles. However, its realization in a homogeneous medium remains challenging due to the absence of strong scattering asymmetry. Here, we introduce an ingenious mechanism to obtain optical pulling and pushing forces using a metasurface-engineered optical field with a tailored longitudinal chirality gradient. This approach exploits parity-asymmetric interactions between chiral particles and the metasurface-engineered needle-like optical field, eliminating the need for complex background structures. Leveraging the field manipulation versatility of spin-decoupled metasurfaces, we demonstrate enantiomer separation across thousands of particle diameters-exceeding previous works by an order of magnitude in terms of particle-scale displacement. Furthermore, by tuning the chirality density of the field, directional control of particle motion can be achieved, underscoring its potential for large-scale chiral sorting and enantioselective drug purification. © 2025 American Physical Society.