1 Department of Electrical and Computer Engineering, Concordia University, Montréal, Canada. steve.shih@concordia.ca.
2 Centre for Applied Synthetic Biology, Concordia University, Montréal, Canada.
3 VERAXA Biotech GmbH, Heidelberg, Germany.
4 Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland. christoph.merten@epfl.ch.

Droplet microfluidics has become a ubiquitous and powerful tool for high-throughput phenotypic screening at the single-cell level. Large numbers of cells can be sorted for a variety of functions, including the secretion of antibodies with tailored properties. The recovery of cells from sorted droplets is still very poor compared to droplet sorting, usually being limited to around 50% of all sorted hits. Here, we present a fully integrated droplet-digital microfluidic platform for the isolation and the recovery of rare single cells and applied our system to antibody discovery. From our work, we have achieved an 18-fold increase in the recovery rate of individual cells and beads from droplets, as compared to conventional methods. We believe that the combination of high-throughput droplet generation with the on-demand control features of digital microfluidics will improve the number of characterized hits in single-cell -omics, antibody screens, directed evolution of enzymes, and beyond.