Particle manipulation using optical nanofibers

Optical trapping has proven to be an efficient method to control particles, including biological cells, single biological macromolecules, colloidal microparticles, and nanoparticles. Multiple types of particles have been successfully trapped, leading to various applications of optical tweezers ranging from biomedical through physics to material sciences. However, precise manipulation of particles with complex composition or of sizes down to nanometer scales can be difficult with conventional optical tweezers, and an alternative manipulation tool is desired. Incorporating optical nanofibers into an optical tweezers setup allows us to overcome some of these limitations. Optical nanofibers have the added advantages of being easily connected to a fibered experimental setup, being simple to fabricate, and providing strong electric field confinement and intense magnitude of evanescent fields at the nanofiber's surface. Many different particles have been trapped, rotated, transported, and assembled with such a system. Here, we discuss some recent observations of microparticle manipulation, such as Janus particle manipulation, negative torque, and transverse spin effects.