Optical transportation and controllable positioning of nanospheres using a microfiber

We experimentally demonstrate an optical transportation and controllable positioning of polystyrene nanospheres using a 3 μm diameter microfiber. By placing the microfiber in a microfluidic channel and injecting a 980 nm laser light into the fiber, nanospheres suspended in the water were stably trapped to the microfiber and delivered along the direction of light propagation. Furthermore, by increasing the velocity of the fluid in the opposite direction of the laser light, it was found that, once the fluid velocity increased to 6 μm/s, spheres stopped their forward progress and halted on the microfiber, so the controllable positioning of spheres along the microfiber was realized.