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NASA GRC has developed several different 3D printing techniques to fabricate polymer aerogel structures; different techniques are suitable for different polymer aerogel formulations. In general, the methods entail forming a first liquid comprising a polymer precursor and cross-linker, forming a second liquid comprising a catalyst for reacting a polymer precursor to form a polymer, then 3D printing the aerogel structure with a mixture of the two liquids onto or into a medium. Specifically, NASA's polymer aerogel 3D printing techniques include: direct syringe printing, dual-syringe printing with static mixing head, direct syringe printing of photocurable formulations, and a unique rapid prototyping method involving a sacrificial bath. The direct syringe process relies upon gelation to occur once the gel is extruded from the print head to the substrate. In the dual-syringe printing process, one syringe contains polyamic acid and the other contains a catalyst. These are mixed in a static mixing head to allow for curing/gelation upon extrusion. For direct syringe printing of photocurable polymer aerogel formulations, a UV pen and array follow the printed gel during extrusion to induce gelation. Finally, the rapid prototyping method uses a bath of highly viscosity, low shear gel that provides a low drag, flexible yet supportive medium in which to print the polymer aerogel. In other embodiments, a bath of polyamic acid is used while cross-linkers and catalysts are introduced via printing, or vice versa (polyamic acid is introduced via printing into a bath of cross-linkers and catalysts). In addition to complex geometries, these layered 3D printing processes allow for the fabrication of chemically-bonded (cross-linked) structures composed of layers of different polymer aerogel formulations (i.e., fabrication of structures with tailored chemistries / properties). Previously, joining different polymer aerogel formulations into a single structure required the fabrication of different formulations using individual molds and joining them using an adhesive, potentially introducing weak fracture points.