Laser light is focused into the hollow region of a capillary fiber at low numerical aperture and transported down the fiber in a grazing incidence mode. In turn the laser light funnels particles from aerosol or aqueous sources into the fiber and guides them along the fiber center. A diverse range of particles can be manipulated including dielectric, semiconductor, and metal spheres ranging from 20 nm to 7 micron in diameter. The spectrum of particles is mainly dependent on laser power, particle composition, and surrounding fluids. The particles may be trapped at specific positions within the fiber by optical levitation or in counter-propagating laser fields.
Laser guidance has advantages over other laser-based manipulation techniques such as laser tweezers.
Particles can be taken from a source chamber and transported to a remote region. This allows the source and trap region to be isolated from each other. The exterior of the fiber can be exposed to a variety of environments without affecting the guidance of particles. Particle trajectories are easily manipulated by mechanical bending of the fiber. Laser guidance uses optical scattering and absorption forces to propel particles along the fiber and gradient forces for confinement to the center.