  Recent advances in Nanotechnologies have prompted the need for tools to
accurately and non-invasively manipulate individual nano-objects. Among
possible strategies, optical forces have been foreseen to provide researchers
with nano-optical tweezers capable to trap a specimen and move it in 3D. In
practice though, the combination of weak optical forces involved and
photothermal issues have thus far prevented their experimental realization.
Here, we demonstrate first 3D optical manipulation of single 50 nm dielectric
objects with near field nano-tweezers. The nano-optical trap is built by
engineering a bowtie plasmonic aperture at the extremity of a tapered
metal-coated optical fiber. Both the trapping operation and monitoring are
performed through the optical fiber making these nano-tweezers totally
autonomous and free of bulky optical elements. The achieved trapping
performances allow for the trapped specimen to be moved over tens of
micrometers during several minutes with very low in-trap intensities. This
novel non-invasive approach is foreseen to open new horizons in nanosciences by
offering an unprecedented level of control of nano-sized objects including
heat-sensitive bio-specimens.
