A novel optoelectronic tweezer using light induced dielectrophoresis

We demonstrate a novel optoelectronic tweezer using light induced dielectrophoresis mechanism to optically trap and transport micro particles with optical power in the μW range. This device consists of two pattern-less surfaces: a bottom glass substrate coated with photoconductive material and a top transparent indium-tin-oxide (ITO) glass. To achieve optical trapping, we sandwich the liquid-immersed micro particles between these two surfaces and supply an ac electric bias. A 633-nm He-Ne laser focused by a 40x objective lens is used to transport the particles. Negative dielectrophoretic trapping is demonstrated in this paper. Our experiment results show that optical beam with power as low as 1 μW is sufficient to transport 25-μm-diameter latex particles at a speed of 4.5 μm/sec. The transport speed increases with higher optical power. A maximum speed of 397 μm/sec is observed at 100 μW.