Generalized Optical Binding for Multiple Assemblies of Nanoparticles under Multiple Laser Beams

Optical forces enable noncontact manipulation of micro- and nanoscale objects, offering diverse applications. When a laser beam irradiates multiple nanoparticles in a solvent, it induces the formation of an ordered array with a finite distance between particles due to optical binding, which results from the optical force exerted by scattered light. This scattered light extends beyond the irradiation area, facilitating interactions between spatially separated nanoparticle assemblies under multiple laser beams. However, the extension of optical binding in this context remains underexplored. In this study, we propose a concept of generalized optical binding between particle assemblies using two focal laser beams. Under carefully designed conditions, the scattered light between assemblies leads the particles to stable positions and impedes rotational dynamics driven by the circular polarization of the lasers. We demonstrate the fusion and reordering of two hexagonal assemblies, offering a blueprint for creating on-demand particle arrays through laser beam manipulation.