  We propose a novel way to trap and manipulate nano-objects above a dielectric
substrate using an apertureless near-field probe. A combination of evanescent
illumination and light scattering at the probe apex is used to shape the
optical field into a localized, three dimensional optical trap. We use the
coupled-dipole method and the Maxwell stress tensor to provide a
self-consistent description of the optical force, including retardation and the
influence of the substrate. We show that small objects can be selectively
captured and manipulated under realistic conditions.
