Numerical design of a plasmonic nano-tweezer for realizing high optical gradient force

Plasmonic tweezers are recently being considered as a promising optical trapping tool because of their absolute advantages over conventional optical tweezing systems. In this article, by exploiting a gold nano-bowtie and a gold nano-ring, we theoretically propose a novel combined nano-tweezing structure that reaps the benefits of both nano-bowtie and nano-ring plasmonic tweezers. Simulations show that the gradient force has increased more than 30 times in the new proposed structure as compared with that in the nano-bowtie structure. Moreover, the designed tweezer can potentially exert trapping force as strong as 3.23 nNW(-1) on a suspended bioparticle with a radius of 10 nm.