On-drop Separation and Sensing with Compound Droplet Microfluidics

We present a new platform for analytical applications of droplet-based microfluidics in which flowing droplets function not only as isolated reaction flasks, but are also capable of on drop separation and sensing. To demonstrate this, ionic liquids with tunable chemical and physical properties have been selected as designer fluids. We create aqueousionic liquid compound droplets with various structures and present two analytical applicationsseparation of a binary aqueous mixture and dynamic pH sensingto highlight the salient features of this scheme. By combining designer fluids with designer microfluidic emulsions, the present work opens a rich space of exploration for analytical microfluidics.