Optical Trapping and Manipulation for Biomedical Applications

The field of optical trapping and manipulation was started in 1970 by Ashkin et al. [1, 2], when the group at Bell Laboratory demonstrated the following:

• A mildly focused laser beam in a sample chamber containing micron-size polystyrene beads suspended in water could attract the bead transversely towards the beam axis and drive the bead to move along the beam axis in the direction of beam propagation (Fig. 14.1a).

• A pair of mildly focused laser beams aligned coaxially and propagating in opposite direction with approximately equal optical power could stably trap a bead (suspended in water) in a three-dimensional space (Fig. 14.1b).

• A mildly focused laser beam directed vertically upward can stably levitate a bead by balancing the radiation pressure against the weight of the bead in water (Fig. 14.1c).