Cell addressing and trapping using novel optoelectronic tweezers

We present novel optoelectronic tweezers (OET) that are capable of trapping and transporting multiple biological cells. This is based on a new mechanism called light induced dielectrophoresis proposed by our group. OET allows a focused optical beam to create a virtual electrode on a photoconductive surface, producing a highly non-uniform electric field. This enables optical addressing of dielectrophoresis forces with a spatial resolution of ∼1 μm. The optical intensity required is three orders of magnitudes lower than that of conventional optical tweezers. By scanning the laser beam, the trapped cells can be moved to any position on a 2D surface. Experimentally, we have successfully demonstrated the concentration and transport of multiple E. coli cells using a HeNe laser with a focused spot size of 17 μm. Optical power as low as 8 μW is sufficient trap the E coli cells.