Plasmonic optical trapping of nanoparticles with precise angular selectivity

In this paper, a plasmonic trapping scheme including a polystyrene nanoparticle with gold cap and a metal tip tweezers was proposed. We numerically investigated the optical trapping behavior of the metal tip to this asymmetric particle. The results show that the metal tip can capture the particle at the position of the gold cap due to the strong plasmonic interaction, while other positions of the particle cannot be captured by metal tip. Furthermore, the trapping angle of the nanoparticle can be adjusted by changing the incident wavelength. Precisely controlling the trapping angle of the nanoparticles in our study has important potential applications of optical tweezers, such as in single molecule manipulation.