Taking advantage of the polarization-dependent light-driven dynamics of gold nanorods

We introduce a multifunctional experimental setup and technique based on holographic curve-shaped laser traps to analyze the dynamics of light-driven colloidal gold nanorods (GNRs). The experimental results, supported by theoretical models and numerical simulations, demonstrate that the transport speed of GNRs along a designed trajectory is influenced by the polarization of light under constant laser power. Specifically, for the considered GNR, the speed was more than twice as fast under linear polarization compared to circular polarization. Moreover, the speed depends on the particle's orientation. When the GNR is aligned with the propulsion direction, its speed is significantly greater than when it is oriented perpendicular to the propagation direction. The dependence of speed on asymmetric particle orientation arises from the interplay between optical and hydrodynamic forces acting on the particle. Furthermore, our study reveals that the dynamics of GNRs in structured traps and their spinning within point-like traps are significantly influenced by particle size and aspect ratio. Despite small statistical fluctuations in particle sizes according to the manufacturer, differences in spinning frequency and translational speed of GNRs from the same set can be effectively quantified, paving the way for dynamic single-particle characterization.