Giant Gradient Force for Nanoparticle Trapping in Coupled Graphene Strips Waveguides

We conduct both analytical and numerical investigations of the giant gradient force for nanoparticle trapping in the coupled graphene strips waveguides system. An analytical model based on coupled slab waveguides has been adopted in the analysis of mode performance and gradient force, and good agreement is obtained with numerical simulations. Both theoretical modeling and numerical simulations have shown that the gradient force can be as high as 8 nN/μm · mW at a gap size of 10 nm, which is at least one order of magnitude higher than the previously reported hybrid plasmonic waveguide. Meanwhile, the giant gradient force leads to an ultrahigh trapping force and potential of 1.5 × 10⁶ fN/W and 2.4 × 10³ k_BT/W, which are three orders of magnitude larger than the hybrid plasmonic waveguides. This enables the efficient trapping of nanoparticles with diameters as small as 2 nm. This coupled graphene strips system opens up new possibilities of tunable nanoscale mechanical devices and various potential applications, such as manipulating biomolecules.