ability to optically trap and manipulate small particles1 using the forces of light has experienced intensivedevelopment in the past years. For example, optical tweezers techniques enable efficient multiple trapping,manipulating living cells or other biological specimens. However, conventional optical tweezers face challenges forthe trapping of nanoparticles because the optical gradient force scales with the particle volume4. Plasmonicnanostructures can overcome the abovementioned difficulties due to their unique ability to confine light into deep subwavelengthvolumes. As a consequence, the enhancement of the local field intensity is due to the coupling of externalelectromagnetic fields to the collective oscillations of the conduction electrons. Therefore, plasmonic nanotweezershave been used to trap and manipulate dielectric4-7. Here, we experimentally demonstrate plasmonic optical tweezersfor nanoparticle trapping based on a metamaterial device. We achieve optical trapping of 20 nm diameter polystyreneparticles with incident trapping intensities (~ 0.80 mW/μm~2) at off-resonant frequencies. A high trap stiffnessenhancement factor of 60 was observed due to the ultra-small mode volume contribution. These results enable precisenanoscale particle trapping and manipulation without damage due to the phototoxic heating effect.
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