Design of a scanning laser optical trap for multiparticle manipulation

In recent years, single-beam optical traps have been used to manipulate individual colloids and biological objects such as cells. We have implemented a rapidly scanning laser optical trap with rates as high as 1200 Hz where a single laser beam is used to trap multiple colloids simultaneously. The optics are optimized to achieve a small laser focus size and a large scanning pattern in the sample. This approach provides great pattern flexibility and, because of the use of piezoelectrics, small particles (1 mu m in diameter) in low-viscosity solvents, such as water, can be readily manipulated. (C) 2000 American Institute of Physics. [S0034-6748(00)01005-4].