Electrokinetic Separation of Polystyrene Microspheres in Conductive Media on a Microfluidic Chip

A polydimethylsiloxane (PDMS)/glass microfluidic chip consisting of a three-layer sandwich structure and a three-parallel micro-electrode system was fabricated for the separation of polystyrene microspheres depending on different the particle size in high conductivity solution by electric field that produced by alternating current. The principle of electrokinetics of microspheres directional movement was investigated in the experiment. The results showed that when the applied voltage was 14 V at 100 kHz, the separation efficiency for the 10-μm and 25-μm polystyrene microspheres was the best. Similarly, with a voltage of 10 V at 2 MHz, the separation efficiency for the 5-μm and 25-μm polystyrene microspheres could achieve the highest. Meanwhile, 11 V at 1 MHz was used for the quick and efficient separation of 5-μm, 10-μm and 25-μm polystyrene microspheres. The separation efficiency of the three groups were all above 90% evenly. At the same time, the formation of the laminar region in the middle of the electrode gap played a key role in the microsphere separation.

The figure shows that the microfluidic chip consisting of a three-parallel micro-electrode system, the electrode was fabricated by Ti-Au-Ti. The microfluidic channels were fabricated by molding poly-dimethylsiloxane (PDMS). Figure 1b shows that the annular liquid flow caused by ACEF exists on top of the parallel and adjacent electrodes, and in the opposite direction. Meanwhile, there was a laminar flow region with a weak ACEF in the gap between the adjacent electrodes.Figure optionsDownload as PowerPoint slide