A bead-in-droplet solution exchange system via continuous flow microfluidic railing

A continuous flow, microfluidic railing system has been developed for the rapid and autonomous exchanges of bead and bead-in-droplet formations. Fluidic encapsulations of microparticles (e.g., microbeads and living cells) inside individual microdroplets provide various possibilities for chemical and biological applications. This work extends the bead-in-droplet technology from a single type droplet to a multiple-stage, different droplet solutions system. A micropost array railing system has been demonstrated to passively: (i) guide an array of bead-in-droplet in a “first” droplet solution to different liquid flows and release the microbeads from the droplets, and (ii) re-encapsulate the released microbeads in droplets containing a different, “second” droplet solution. Experimental results revealed successful continuous flow solution exchanges for water-in-oil droplets with size of about 60.2μm in diameter containing microbeads of 15μm in diameter.