Droplet microfluidics for high-throughput analysis of cells and particles

Droplet microfluidics (DM) is an area of research which combines lab-on-a-chip (LOC) techniques with emulsion compartmentalization to perform high-throughput, chemical and biological assays. The key issue of this approach lies in the generation, over tens of milliseconds, of thousands of liquid vessels which can be used either as a carrier, to transport encapsulated particles and cells, or as microreactors, to perform parallel analysis of a vast number of samples. Each compartment comprises a liquid droplet containing the sample, surrounded by an immiscible fluid. This microfluidic technique is capable of generating subnanoliter and highly monodispersed liquid droplets, which offer many opportunities for developing novel single-cell and single-molecule studies, as well as high-throughput methodologies for the detection and sorting of encapsulated species in droplets. The aim of this chapter is to give an overview of the features of DM in a broad microfluidic context, as well as to show the advantages and limitations of the technology in the field of LOC analytical research. Examples are reported and discussed to show how DM can provide novel systems with applications in high-throughput, quantitative cell and particle analysis.