Figure 12.

(a) Localized fusion and merging of the two adjacent drops; (b) Blocking the first drop by a laser valve until the second drop arrives and merging the two by another laser beam at the interface; (c) A droplet sampler that decides precisely what portion of the drop should go to each specific outlet. Republished with permission of Royal Society of Chemistry, from [140], “An optical toolbox for total control of droplet microfluidics”, C.N. Baroud, M.R. de Saint Vincent, and J.-P. Delville, Lab on a Chip, vol. 7, pp. 1029–1033, 2007; Permission conveyed through Copyright Clearance Center, Inc.