Reduction of nonspecific surface-particle interactions in optoelectronic tweezers

We demonstrate three-dimensional optoelectronic tweezers (3D OET) for the adsorption-free manipulation of microparticles. In typical OET, nonspecific interactions between the manipulated particles and the device surfaces, such as hydrophobic, Van der Waals, and electrostatic interactions, interfere with the effective microparticle manipulation. Here, by using the 3D OET device, which is composed of two photoconductive layers, we succeeded in three-dimensional focusing and manipulating polystyrene microbeads in a channel-less microenvironment without the particle adsorption. The 3D OET with the light-induced negative dielectrophoresis also shows a higher particle trapping efficiency and less particle adsorption rate than typical OET. (c) 2008 American Institute of Physics.