  Controlling the transport, trapping, and filtering of nanoparticles is
important for many applications. By virtue of their weak response to gravity
and their thermal motion, various physical mechanisms can be exploited for such
operations on nanoparticles. However, the manipulation based on optical forces
is potentially most appealing since it constitutes a highly deterministic
approach. Plasmonic nanostructures have been suggested for this purpose, but
they possess the disadvantages of locally generating heat and trapping the
nanoparticles directly on surface. Here, we propose the use of dielectric rings
made of high permittivity materials for trapping nanoparticles. Thanks to their
ability to strongly localize the field in space, nanoparticles can be trapped
without contact. We use a semi-analytical method to study the ability of these
rings to trap nanoparticles. Results are supported by full-wave simulations.
Application of the trapping concept to nanoparticle filtration is suggested.
