Controlled Generation of Double Emulsions for Laser Fusion Target Fabrication Using a Glass Capillary Microfluidic Device

We report the controllable generation of double emulsions for target fabrication using glass capillary microfluidic devices. Instead of a conventional triple-orifice droplet generator, user-friendly glass capillary devices are used to produce micrometer to millimeter-sized water-in-oil-in-water emulsions. The double emulsions have a relatively uniform size distribution with an average outer diameter of 1420 μm. The sizes of the emulsions can also be varied by changing the ratio of the inner, middle, and outer fluids. Increasing the flow rate ratio of the outer fluid to the other fluids [Q_o/(Q_m+Q_i)] from 3 to 11, the outer radii of the emulsions decrease from 1120 to 950 μm. On the other hand, increasing the flow rate ratio of the middle fluid to the inner fluid (Q_m/Q_i) from 0.7 to 1.6, the aspect ratio of the emulsions increases from 4 to 8. Our experimental values are in good agreement with a simple theoretical model. These results suggest that our present method to control the generation of double emulsions can be used as an alternative approach to fabricate polystyrene targets for future laser fusion experiments.