Water-encapsulated microbubbles (gas-in-water-in-oil) are fabricated using two different microfluidic approaches. By adjusting the flow rate ratio of water to oil the number of encapsulated microbubbles in micrometer-size water droplets and the thickness of the water layer can be controlled. Adding photopolymerizable monomers into the water phase permits polymerization of the aqueous droplets encapsulating the microbubbles yielding porous polymer microparticles.