| In nature fluid transports often exists in the form of droplets. From the formation of clouds to the condensation of dews on leaves, droplets are formed spontaneously in air, on solid and in immiscible fluids. In biological systems, droplets with lipid bilayer membranes are used to transport sub-nano liters of reagents between organelles, between cells, and between organs, which have been utilized to a fine degree to control our day to day metabolic activities. The precision of these systems are self-evident and proves that droplet based systems are intrinsically efficient in controlled transport, reactions, and signaling.; This precision and efficiency can be channeled into many lab on chip applications through manipulating individual droplets using microfabricated force gradients. Complex segmented flow processing of generating, fusing, splitting, and sorting droplets have been developed to digitally control fluid volumes and concentrations of nanoliter variations. Design principles and criteria are analyzed in details and applied to advance current biomedical applications. |
