Formation of microdroplets in liquids utilizing active pneumatic choppers on a microfluidic chip

Monodispersed emulsions are of great significance for a variety of applications. The current study reports a new microfluidic system capable of formation of microdroplets in liquids for emulsification applications. This new emulsion chip can precisely generate uniform droplets using a novel combination of hydrodynamic-focusing and liquid-chopping techniques. Experimental data show that microdroplets with diameters ranging from 6 to 100 pill with a variation less than 3% can be precisely generated. The size of the droplets is tunable using three approaches including adjusting the relative sheath/sample flow velocity ratios, the applied air pressure and the applied chopping frequency. Moreover, focusing and chopping of multiple flows has been demonstrated to increase the emulsion process throughput.