High-Purity Separation of Rare Species in Droplet Microfluidics using Droplet-Conduit Structures

We present a technique to achieve high-purity isolation of the target species in electrowetting-on-dielectric (EWOD)-based droplet microfluidics by forming a long and slender liquid path between droplets that acts as a "conduit" for actively transported target species, while minimizing non-specific transport due to diffusion and fluidic movement. By stabilizing the conduit chemically (e.g., using surfactants) and controlling the fluid by EWOD, we demonstrate, as an example, very high magnetic bead (MB) collection efficiency (≫ 99%) while eliminating ~97% non-magnetic beads (nonMBs) in just one separation step.