Contiunous micro-particle separation using optically-induced dielectrophoretic forces

The current study presents new methods to quickly separate micro-particles with different sizes using optically-induced dielectrophoretic (ODEP) forces. It was found that the strength of the ODEP force induced on the hydrogenated amorphous silicon surface is determined by the wavelength of the illuminating patterns. Therefore two moving lines and one stationary illuminated line which produced the ODEP forces as virtual electrodes were first defined by projecting lights onto a photoconductive chip. The moving lines and one stationary illuminated line were used to generate a stronger and a weaker ODEP force, respectively. As the moving lines approached to the weaker line, micro-particles between them were concentrated by the higher ODEP forces and squeezed through the stationary electrode. Finally, lager micro-particles were subsequently separated from the smaller particles. With this approach, continuous particle separation can be automatically achieved in a short period of time. This developed method may be promising for a variety of applications such as cell-based assays and sample pre-treatment using micro-particles.