Optically Bound Rapid Plasmonic Nanorod Dimers: Anisotropic Dynamics Driven by Light‐Fluidic Cooperation

ABSTRACT Optical manipulation enables controlled assembly of colloidal particles, facilitating light‐mediated interactions relevant to optically driven technologies. Most studies focus on isotropic plasmonic nanospheres, whereas controlled optical actuation of anisotropic nanoparticles such as gold nanorods (GNRs) remains underexplored. We demonstrate that GNRs confined in custom‐designed dynamic optical traps exhibit cooperative behavior driven by optical binding, propulsion forces, torques, and near surface hydrodynamic interactions. These mechanisms enable the reversible formation of mobile optically bound (OB) GNR dimers in end‐to‐end configurations, with interparticle separations close to the trapping wavelength in the medium. The assemblies display strong anisotropic dynamics, including orientation‐dependent propulsion and transport velocities up to four times higher than isolated GNRs. Dimer velocity varies by a factor of two depending on its alignment with the propulsion force. We investigate these dynamics using polygonal laser traps with tailored phase‐gradient propulsion forces and fast orientation resolved optical tracking that enables studying in situ creation and optically guided motion of OB dimers. Combined experimental and theoretical analysis reveals how propulsion, confinement, and hydrodynamic conditions determine binding distance and transport behavior. The developed approach disentangles optical, thermal, and fluidic contributions, providing quantitative insight into light‐driven anisotropic assemblies for nanoscale transport and adaptive colloidal systems.