In this work the effect of the dielectrophoretic force (DEP) in the self-assembly process of nanoparticles electrosprayed onto a substrate, is examined. DEP force is originated by the electric field created by the electrospray gun and by the distortion of the field created by the effective dipole of each nanoparticle. It is also shown that the modulus of this force is large when the distance between particles is few times its diameter, provided the medium is wet and the electric field is not switched off. The directional nature of DEP In this wet phase, is shown to chain nanoparticles aligned with the main electric field direction. Although there is a repulsive force between chains in the orthogonal direction to the field, it is minimum when the beads align with the voids in the nearby chains. DEP is a dominant force in the close distances of nanoparticles compared to double layer, van der Waals, electrophoretic retardation, weight and buoyancy.