Support-free scalable 3D printing of photothermal composite material for robust adaptive construction in extreme conditions

Abstract

For unmanned lunar construction, 3D printing offers the ability to fabricate complex geometries such as domes and cantilevers. However, the flowable materials required for such printing are susceptible to vacuum-induced shape instability and often necessitate sacrificial supports that complicate processes and waste material. This work proposes a design scheme for a photothermal-hardened composite material (PTHC) and integrates it with direct ink writing (DIW) to achieve stable, support-free digital construction under high vacuum and drastic temperature fluctuations. Specifically, ultraviolet irradiation triggers second-scale surface curing (within 5 s), forming a protective skin that both shields the extruded material from extreme environments and maintains its initial shape. Subsequent in-situ heating (approximately 100 °C) induces minute-scale internal thermal curing (within 5 min), yielding an outstanding mechanical strength of ~170 MPa. Using this strategy, we successfully fabricated meter-scale self-supporting cantilever beams and other complex structures. Notably, the superior service performance of the designed PTHC is reflected in its unique combination of excellent vacuum stability, thermal shock resistance, radiation tolerance, and dynamic impact resistance. This photothermal dual-curing strategy establishes a support-free and environment-adaptive DIW paradigm, providing a scalable pathway for robust in-situ construction on the lunar surface.