Deformability-based separation of microgels using microfluidics

Droplet microfluidics has the potential to increase the throughput of biomolecule screening. However, current on-chip passive droplet sorting methods have throughputs significantly below standard active fluorescence activated droplet sorting techniques. Here, we present an asymmetric microfluidic T-junction to separate picoliter sized microgels based on their deformability. We experimentally characterize the motion and deformation of microscale agarose hydrogels transported at low Re through microchannels. Microgels of different stiffnesses are separated based on their deformation and relaxation after leaving the T-junction. With increasing rigidity, we observe that microgels shift their exit from the right outlet to the top outlet in the device at a constant flow rate. We demonstrate that sorting of microgels can be tuned by altering their viscoelasticity relative to the continuous oil phase. Our results can provide insights to the label-free, high-throughput, passive separation of monodisperse droplets for protein screening and directed evolution of enzymes.