Review and analysis of performance metrics of droplet microfluidics systems

Droplet microfluidics has enabled many recent applications in high-throughput screening and diagnostics. Little work has been done, however, to analyze the performance of droplet-based assays. This review aims to apply what is known in the literature to the analysis of the performance metrics of droplet-based assays, with specific relevance to diagnostic and biomedical applications based on two processes: enzymatic reactions and cell culture in droplets. By considering the physical scaling of individual processes—droplet generation, reaction kinetics, cell growth, and droplet interrogation—it is possible to extract a practical relationship between input parameters (e.g., droplet size and droplet polydispersity) and the output characteristics (e.g., throughput, dynamic range, and accuracy) of the assay. This review can serve as a guide to the design of droplet-based assays for achieving desired performance. While the focus is on assays based on enzymatic reactions and cell cultures, a similar analysis can be applied to other assays based on polymerase chain reaction and the detection of nucleic acids.