Viscoelasticity-dependent, deformation-based sorting of microgels using sequential bifurcations.

Droplet-based microfluidics have accelerated the discovery of rare variants in large combinatorial protein libraries by enabling high-throughput screening in miniaturized reaction systems. However, throughput limitations and assay compatibility constrain the accessible sequence space and the diversity of enzyme classes amenable to droplet-based screening. Passive, deformability-based sorting systems offer scalability via microfluidic parallelization, but existing platforms lack the sensitivity and throughput required for efficiently exploring vast fitness landscapes. In this work, we present a microfluidic device for passively sorting monodisperse microgels based on their deformability using sequential bifurcations, with a throughput up to 300 Hz. Extension-dominated flow in a T-shaped junction enables rapid microgel deformation, leading to viscoelasticity-dependent trajectories under finite flow inertia. To investigate the relationship between microgel viscoelasticity and sorting performance, we characterized the transit dynamics of a model system of agarose microgels. We demonstrated the ability to rapidly isolate highly viscous agarase-degraded microgels from highly elastic 1% agarose microgels with 99.3% accuracy. Our design has promise for expanding the capabilities of droplet-based screening for enzyme-mediated polymerization or degradation assays.