Integration of inertial microchannels and droplet generators for controlled encapsulation of single cells

In this presentation, we describe a method for controlled encapsulation of single cells in micro-droplets by combining straight inertial micro-channels and flow-focusing droplet generators. Under fluid mechanical inertia, particles migrate toward inertial equilibrium positions inside the microchannel and form ordered trains of particles (cells). First we use microfluidic experiments and discrete-particle lattice-Boltzmann simulations to describe the pair trajectory attractors which lead to formation of trains with preferred spacing between particles. Then we illustrate that train formation can be utilized to modulate the entry frequency of cells into a flow focusing droplet generator. Considering the inertia of the cell-laden fluid, we control the wall-confinement in the orifice to segment the suspending fluid into uniform size droplets without forming stable or undulating jets. We show the capability of inertial microfluidic systems in controlled encapsulation of single cells in droplets for various cancer cell lines and human bone-marrow stem cells suspended in Newtonian Phosphate Buffered Saline (PBS) and weakly viscoelastic pre-gel fluids.