A Simple System for In-droplet Incubation and Quantification of Agglutination Assays

This work reports on a simple system for quantitative sensing of a target analyte based on agglutination in microchannels. Functionalized microbeads and analyte with no prior incubation are flowed in droplets (~2μL) through a thin silicone tube filled with mineral oil at a flow rate of 150 μL/min. Hydrodynamic forces alone produce a highly efficient mixing of the beads within the droplet, without the need of complex mixing structures or magnetic actuation. The setup allows rapid observation of agglutination (<2 min), which is quantified using image analysis, and has potential application to high-throughput analysis.