An interfacial technique utilizes hydrodynamic micro-vortices to perform (i) high efficiency single cell encapsulation and (ii) size-selective capturing of cells based on their sizes in a single microfluidic device. A notable feature of this technique is that it can perform high efficiency single cell encapsulation at low cell concentrations, and this technique is all passive, controlled only by the flow rates of the two phases and does not require complex structures or on-chip active devices. Single bead/cell encapsulation was demonstrated at 50% efficiency, which is at least 10 times greater than the random encapsulations at the introduced cell concentrations. Also demonstrated is the selective trapping of cells based on their sizes. This present technique expands the capabilities of droplet microfluidics for applications ranging from single cell genomics, proteomic assays to sample preparation.
