Microfluidic high-throughput encapsulation and hydrodynamic self-sorting of single cells

We present a purely hydrodynamic method for the high-throughput encapsulation of single cells into picoliter droplets, and spontaneous self-sorting of these droplets. Encapsulation uses a cell-triggered Rayleigh-Plateau instability in a flow-focusing geometry, and self-sorting puts to work two extra hydrodynamic mechanisms: lateral drift of deformable objects in a shear flow, and sterically driven dispersion in a compressional flow. Encapsulation and sorting are achieved on-flight in continuous flow at a rate up to 160 cells per second. The whole process is robust and costeffective, involving no optical or electrical discrimination, active sorting, flow switching, or moving parts. Successful encapsulation and sorting of 70-80% of the injected cell population into drops containing one and only one cell, with 10,000-fold enrichment as compared with the initial mix. The method can be implemented in simple 'soft lithography' chips, allowing for easy downstream coupling with microfluidic cell biology or molecular biology protocols. droplets | Rayleigh-Plateau | size-fractionnation | digital microfluidics