Development of a novel ODEP chip using polymer photoconductive material and FTO electrode

A novel ODEP (optical dielectrophoresis) chip using a polymer photoconductive material and fluorine doped tin oxide (FTO) conductive film is demonstrated to manipulate micron-sized polystyrene beads. Instead of using the traditional hydrogenated amorphous silicon (a-Si:H) as photoconductive layers, a thin film of a mixture of poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methylester (PCBM) photoconductive polymer is used in this novel ODEP chip. When the polymer layer is illuminated by a light beam, many electron-hole pairs are created, which increase the conductivity of the polymer. Consequently, localized non-uniform electric field can be generated when an AC bias is applied across the ODEP chip, and localized DEP forces are then generated. The distribution of electrical field induced by a ring-shaped optical electrode is simulated and the maximum trapping velocity is calculated according to Stokes' law for this ODEP chip. The effect of the polymer thickness to the magnitude of the generated DEP force has also been investigated. The maximum trapping velocity and the induced DEP force exerted on 20 µm polystyrene beads are estimated to be 77 µm/s and 15 pN, respectively. Finally, performance of the polymer-based ODEP chip is compared with an a-Si:H-based ODEP chip by trapping and sorting polystyrene beads with identical parameters. The experimental results indicate that the polymer photoconductive material used in our work is promising for rapid fabrication of ODEP chips for microparticles manipulation.