Concentric electrodes improve microfluidic droplet sorting.

Microfluidic droplet sorting allows selection of subpopulations of cells, nucleic acids, and biomolecules with soluble assays. Dielectrophoresis is widely used for sorting because it generates strong forces on droplets, actuates rapidly, and is easy to integrate into microfluidic chips. However, existing device designs apply a short force, limiting the deflection of droplets, and therefore the speed and reliability of sorting. We describe a concentric design that applies a long force, allowing large deflections and increased reliability. We demonstrate the utility of this design by sorting polydisperse emulsions, which are typically difficult to sort with high purity.