Mediating millisecond reaction time around particles and cells.

Precise spatiotemporal control of how particles and cells interact with reagents is critical for numerous laboratory and industrial processes. Novel tools for exerting this control at shorter time scales will enable development of new chemical processes and biomedical assays. Previously, we have developed a generalized approach to manipulate cells and particles across fluid streams termed rapid inertial solution exchange (RInSE), which utilizes inertial lift forces at finite Reynolds number and high Peclet number to transfer particles from an initial solution to another within a millisecond. Here, we apply these principles toward developing a continuous flow microfluidic platform that enables transient chemical treatments of cells and particles (on the order of 1 ms). We also demonstrate how the reactant stream can be employed as a diffusion barrier, preventing adverse reactions between coflowing solutions. In order to demonstrate the utility of the method, we applied it to various operations in molecular biology and automated cell staining including cell permeabilization, fluorescent staining, and molecular delivery to viable cells. We expect this method will enable previously unexplored studies of the dynamics of molecular events, improve uniformity of reactions carried on the surface of beads, and increase uniformity in cell-based assays through automation.