A microfluidic platform for manipulation and separation of oil-in-water emulsion droplets using optically induced dielectrophoresis

A microfluidic platform for manipulation and separation of oil-in-water emulsion droplets by using optically induced dielectrophoresis (ODEP) is reported in this study. By utilizing different scanning speeds of a moving light beam, the oil-in-water emulsion droplets can be moved and separated with a high separation resolution. A first demonstration of this platform is pre-separation and fine separation of emulsion droplets. Three groups of droplets with different sizes (40-43, 20-30 and 2-8 mu m) can be roughly separated first. The fine separation of emulsion droplets with a radius difference of 2.5 mu m can be performed using a moving light beam with a gradual gradient of moving speeds. To avoid the collision and overlapping of the droplets, a new approach to assign individual moving track for each droplet was adopted by using well-defined moving light patterns. Accordingly, droplets with five different sizes (30, 20, 10, 7.5 and 5 mu m) can be successfully separated. The second demonstration is to separate satellite and master emulsion droplets generated from microfluidic emulsion chips. The developed platform has a great potential to control the quality of emulsion droplets.