Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Gradient forces on double negative (DNG) spherical dielectric particles are theoretically evaluated for v-th Bessel beams supposing geometrical optics approximations based on momentum transfer. For the first time in the literature, comparisons between these forces for double positive (DPS) and DNG particles are reported. We conclude that, contrary to the conventional case of positive refractive index, the gradient forces acting on a DNG particle may not reverse sign when the relative refractive index n goes from vertical bar n vertical bar > 1 to vertical bar n vertical bar < 1, thus revealing new and interesting trapping properties. (C) 2010 Optical Society of America18232428724292Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CePOF, Optics and Photonics Research Center [2005/51689-2]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2009/54494-9]CePOF, Optics and Photonics Research Center [2005/51689-2]