Applicability of UV-Curable Binders in High Solid Suspensions for Direct-Ink-Write 3D Printing in Extremely Cold Temperatures.

Leveraging material extrusion 3D printing of high solid suspensions for rapid manufacturing in future space missions requires materials compatible with the unique environments found on the Lunar surface. However, there is currently a lack of selection criteria for materials processable in the harsh environmental conditions on the Moon without significantly altering the 3D printers. Here, we provide valuable insights into the behavior of high solid suspensions at low temperatures to guide informed decision-making for manufacturing in subzero environments. We investigate the effects of direct-ink-write (DIW) printing at -30 °C on the structure-property relationships of UV-curable high solid inks of glass microspheres. We analyze the inks based on extrudability and curability at subzero temperatures to verify extrusion, shape retention, and sufficient solidification, culminating in successful printing at -30 °C. Preferential polymerization among monomers is observed at -30 °C and results in a lower cross-linking density in the final print, with a reduced tensile modulus. However, lower ratios of highly mobile monomers result in the retention of mechanical properties, demonstrating the selection criteria for binder design. Through this work, we highlight the importance of binder formulations used for 3D printing in uncommon environmental conditions that are emerging as tomorrow's manufacturing challenge.