Plasmonic trapping with a gold nanopillar.

An improved ability to manipulate nanoscale objects could spur the field of nanotechnology. Optical tweezers offer the compelling advantage that manipulation is performed in a non-invasive manner. However, traditional optical tweezers based on laser beams focused with microscope lenses face limitations due to the diffraction limit, which states that conventional lenses can focus light to spots no smaller than roughly half the wavelength. This has motivated recent work on optical trapping based on the sub-wavelength field distributions of surface plasmon nanostructures. This approach offers the benefits of higher precision and resolution, and the possibility of large-scale parallelization. Herein, we discuss the fundamentals of optical manipulation using surface plasmon resonance structures. We describe two important issues in plasmonic trapping: optical design and thermal management strategies. Finally, we describe a surface plasmon nanostructure, consisting of a gold nanopillar that takes these issues into consideration. It is shown to enable the trapping and rotation (manual and passive) of nanoparticles. Methods by which this concept can be extended are discussed.