Size-dependent trapping and delivery of submicro-spheres using a submicrofibre

We report size-dependent trapping and delivery of polystyrene submicro-spheres using a 600 nm diameter fibre. Theoretical results show that both gradient and scattering forces exerted on polystyrene submicro-spheres by the evanescent wave field around the submicrofibre increase with an increase in the sphere diameter, and the delivery velocity of the bigger spheres is also higher than that of smaller spheres. To support the theoretical predictions, experiments were performed using polystyrene spheres with diameters of 230, 400, 530 and 700 nm by injecting a 532 nm green laser into the fibre. The results demonstrate that spheres with larger diameter can be more easily trapped to the surface of the fibre and delivered in the propagation direction of the laser at a low input laser power.