A capillary microfluidic device comprised two tapered cylindrical glass capillaries coaxially assembled in a square capillary (fig. S1). The cylindrical capillaries were tapered by a puller (P-97, Sutter Instrument) and sanded to have a diameter of either 200 or 280 μm. The inner wall of the cylindrical capillary with a 200-μm orifice was first treated with 2-[methoxy(polyethyleneoxy)propyl] trimethoxy silane (Gelest Inc.) to render the surface hydrophilic, and then, the outer wall was treated with trimethoxy(octadecyl)silane (Sigma-Aldrich) to render the surface hydrophobic. The whole surfaces of the capillary with a 280-μm orifice were treated with 2-[methoxy(polyethyleneoxy)propyl] trimethoxy silane (Gelest Inc.) to render them hydrophilic. Afterward, two cylindrical capillaries were coaxially assembled in the square capillary to have a tip-to-tip alignment with a separation of 200 μm. The innermost CLC solution and an aqueous solution for the inner shell were simultaneously injected through the cylindrical capillary with the 200-μm orifice, and the silicone monomer for the outer shell was injected through the interstice between the cylindrical and square capillaries. At the same time, the continuous phase was injected through the interstice between the cylindrical capillary with the 280-μm orifice and square capillary as a counterflow. Flow rates of the four fluids were typically set to 120, 200, 300, and 3200 μl hour−1 from the innermost to the continuous phase using syringe pumps (KD Scientific Inc.). The formation of triple-emulsion drops was observed with an optical microscope (TS100, Nikon) equipped with a high-speed camera (MotionScope M3, Redlake). The outer shell was polymerized by irradiating the droplets with UV (CoolWave UV Curing System, Nordson) for 2 min after collecting the drops. The resulting capsules were suspended in the aqueous solution of 5% (w/w) of PVA and 4% (w/w) of glycerol, which leads to the floatation of CLC-loaded capsules made from the triple-emulsion drops and the sedimentation of CLC-free capsules from the double-emulsion drops due to the difference in average density.

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