Nanoparticle Enrichment by the reversal AC Electroosmotic Flow

Microfluidic devices provide advantages such as rapid reactions, portability, less sample volume, and the availability of on-chip multi-functional integration. A particle control in the microfluidic platform often brings beneficial effects for improved performance of the device or highly sensitive analysis. This study demonstrates a novel approach for nanoparticle enrichment driven by the reversal alternating current electroosmotic flow (rACEO). The process of nanoparticle enrichment in a microfluidic device embedded with a coplanar symmetric electrode array was examined. Nanoparticles in a solution were driven by rACEO to be concentrated into the electrode's gap at a high-frequency range of AC signal, typically 50-150 kHz. We could achieve over tenfold rise in the concentration of polystyrene particles having a diameter of 100 nm from the initial concentration. This result demonstrates a potential application of rACEO for focusing rare species in the sample in the way to enhance the detection sensitivity.