The integration of multibarrel glass capillaries into a microfluidic co-flow configuration is demonstrated for parallel production of nanoliter scale droplets. The multibarrel system supports the generation of a continuous stream of single-phase or dual-phase droplets with digital control over droplet content, enabling the formation of dynamically-programmable and tunable emulsions. The multibarrel capillary method allows simultaneous generation of multiple droplets from parallel droplet generators, with controlled switching between selected dispersed phase or continuous phase compositions. Individual phases emerging from each capillary outlet may be selected to yield merged droplets combining continuous phase emitted from one or more neighboring droplet generators. Because the capillary emitters are configured in a two dimensional array, the multibarrel system provides greater flexibility toward producing controlled interactions between multiple solutions and phases than conventional planar microfluidic droplet generators. Using a 7-barrel capillary configuration, the ability to regulate droplet composition and particle size of individual as well as combined single and merged water-in-oil droplets is explored, together with the use of two-dimensional spatial control within the multibarrel array to generate higher order emulsions. (C) 2015 Elsevier B.V. All rights reserved.