Passive microfluidic channel geometries for control of droplet fission, fusion and sorting are designed, fabricated, and tested. In droplet fission, the inlet width of the bifurcating junction is used to control the range of breakable droplet sizes and the relative resistances of the daughter channels were used to control the volume of the daughter droplets. Droplet fission is shown to produce concentration differences in the daughter droplets generated from a primary drop with an incompletely mixed chemical gradient, and for droplets in each of the bifurcated channels, droplets were found to be monodispersed with a less than 2% variation in size. Droplet fusion is demonstrated using a flow rectifying design that can fuse multiple droplets of same or different sizes generated at various frequencies. Droplet sorting is achieved using a bifurcating flow design that allows droplets to be separated base on their sizes by controlling the widths of the daughter channels. Using this sorting design, submicron satellite droplets are separated from the larger droplets.

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We review theoretical and numerical studies and methods for droplet deformation, breakup and coalescence in flows relevant to the design of micro channels for droplet generation and manipulation.

Nano-sized lipid vesicles with tailored properties have been used as building blocks to generate lipid tubules between two glass surfaces. The tubules formed not only have defined orientation, width, and length, but they can also grow to be as long as 13 mm under ambient conditions, without externally supplied flow, temperature control, or catalyzing agents. Tubule membrane and its internal aqueous content can be manipulated by controlling the combination of different vesicle's lipid composition and aqueous entrapment. This self-assembly process opens up new pathways for generating complicated and flexible architectures for use in biocompatible molecular and supramolecular engineering. We demonstrated these possibilities by generating tubules encapsulated with siRNA, tubules with multiple branches, and polymerized fluorescent tubules in a single-throughput self-assembly process.