High-Order Multiple Emulsions Formed in Poly(dimethylsiloxane) Microfluidics
microfluidics, multiple emulsions, photoresponsive materials, sol–gel processes, wettability
Droplets encapsulated multiple times in droplets of alternating kinds of fluids (oil, water) were emulsified in a highly controlled way. PDMS microcapillary devices were used to guarantee monodispersity of higher order emulsions, at the expense of large quantity formation.
Results and Discussion
A single emulsion of water droplets in fluorocarbon oil (w/o) is formed by injecting water at 200mL/h in the first inlet of a microtube and oil in a second inlet at 400mL/h (Fig. 1a). The single drop maker has uniform hydrophobic wettability. To form a double emulsion of o/w/o a third inlet is added to the linear drop maker where the fluid is injected at 600mL/h (Fig. 1b). By adding even more inlets and controlling the fluid speeds at each inlet even triple, quadruple and quintuple emulsion were formed (Fig. 1c-e).
In that way monodisperse higher order emulsion can be formed. Since the microcapillary devices fabrication is very difficult the scalability of the emulsification process is restricted. Linear arrays of poly(dimethylsiloxane) (PDMS) drop makers with alternating wettability were fabricated such that drops form from each channel.