Optical Trapping Force on a Plasmonic Substrate

Optical trapping is currently widely applied in the field of biotechnology, in which one critical issue is to manipulate cells in the micron-size scale without hurting or damaging them. The plasmonics-assisted optical trapping method is considered to be very promising for achieving more precise trapping of small particles compared to the conventional optical trapping method. In this project, the optical force exerted by an optical beam on a dielectric bead trapped on a substrate proliferated with nanometric gold-pillar pairs is numerically simulated in COMSOL Multiphysics environment. The numerical results show a clearly enhanced trapping capability, which is quantitatively manifested by a ten times higher trapping stiffness as compared to the scenario without the plasmonic-pillar pairs. The simulation results therefore prove that, given the same incident light condition, an appropriately designed nanometric plasmonic substrate can achieve a significantly higher trapping precision albeit Brownian motion; hence less heating damage will be induced in the trapping process, which can be vital for manipulating living cells in biotechnology