1 nm-Resolution Sorting of Sub-10 nm Nanoparticles Using a Dielectric Metasurface with Toroidal Responses

Sorting nanoparticles is of paramount importance in numerous physical, chemical, and biomedical applications. Current technologies for sorting dielectric nanoparticles have a common size limit and resolution approximately of 20 and 10 nm, respectively. It remains a grand challenge to push the limit. Herein, the new physics that deploys toroidal and multipole responses in a dielectric metasurface to exert strong and distinguishable optical forces on sub-10 nm nanoparticles is unravelled. The electric toroidal dipole, electric dipole, and quadrupole emerge with distinct light and force patterns, which can be leveraged to promise unprecedented high-precision manipulations, such as sorting sub-10 nm polystyrene nanoparticles at 1 nm resolution, sorting 20 nm proteins/exsomes at 3 nm resolution, conveying, and concentrating 100 nm gold nanoparticles. Remarkably, the design can also be employed to screen out medium-sized nanoparticles from a mixture of nanoparticles with over three sizes. This optofluidic manipulation platform opens the new way to explore intriguing optical modes for the powerful manipulation of nanoparticles with nanometer precisions and low laser powers.

Automated summary

Sorting nanoparticles is crucial in various fields such as physics, chemistry, and biomedicine. However, current sorting technologies for dielectric nanoparticles have limitations in size and resolution. This study reveals a new physics based on toroidal and multipole responses in a dielectric metasurface, enabling precise manipulation of sub-10 nm nanoparticles with low laser powers. The design can achieve high-resolution sorting and concentration of different sized nanoparticles, opening up new possibilities for optical manipulation of nanoparticles at nanometer scale.