An additive manufacturing (AM) system and method configured to fabricate a 3D printed object from a liquid photocurable composition is provided. The AM system comprises a gas sphere assembly and an AM assembly. The gas sphere assembly comprises a prep chamber and a generation system having a generation chamber including a gas sphere generation unit, a jet source chamber including a sphere unit, and a gas chamber, a reservoir, and a gas cylinder. When a gas is fed to the gas chamber and the liquid photocurable composition is fed to the jet source chamber and generation chamber, the gas is pushed through a plurality of first openings of the sphere unit, and then a plurality of micro-openings of the gas sphere generation unit, to generate the plurality of closed-packed gas spheres. The plurality of closed-packed gas spheres are employed in the AM system for fabrication of the 3D printed object.