A microfluidic chip for formation and collection of emulsion droplets utilizing active pneumatic micro-choppers and micro-switches

The formation of emulsification droplets is crucial for many industrial applications. This paper reports a new microfluidic chip capable of formation and collection of micro-droplets in liquids for emulsion applications. This microfluidic chip comprising microchannels, a micro-chopper and a micro-switch was fabricated by using micro-electro-mechanical-systems (MEMS) technology. The microfluidic chip can generate uniform droplets with tunable sizes by using combination of flow-focusing and liquid-chopping techniques. The droplet size can be actively fine-tuned by controlling either the relative sheath/sample flow velocity ratios or the chopping frequency. The generated droplets can be then sorted to a specific collection area utilizing an active pneumatic micro-switch formed with three micro-valves. Experimental data showed that the olive oil and sodium-alginate (Na-alginate) droplets with diameters ranging from 3 μm to 70 μm with a variation less than 14% is successfully generated and collected. The development of this microfluidic system can be promising for emulsion, drug delivery and nano-medicine applications. © Springer Science+Business Media, LLC 2008.