Wenqiang Zuo

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.

Geopolymers offer a promising pathway for low-energy lunar construction, though their practical application is limited by the high cost of Earth-Moon transportation and extreme lunar conditions, particularly water scarcity, which necessitate high material robustness and extensive in-situ resource utilization. In this work, we develop an ultra-low water consumption geopolymer (ULWG) based on a typical lunar regolith simulant CUG-A. Using a compressible packing model (CPM) combined with press molding, we achieved a maximum particle packing fraction of 78.8%, representing a 26.7% enhancement over non-optimized conditions. The mixture was then cured at 80°C to accelerate, leading to the formation of alkaline aluminosilicate hydrate, as verified by mineralogical and functional group analyses. The resulting ULWG reached a mechanical strength of 20 MPa within 72 hours. To further reduce water demand, we introduced an improved full-process thermoforming strategy that employs higher temperatures and a saturated alkali activator, lowering water consumption to just 3% and achieving over 90% in-situ resource utilization. We also assessed the material’s performance under high vacuum and large temperature variations, observing a strength retention rate above 90% after 7 days. This study demonstrates the highest reported 72-hour strength per unit alkali activator solution (AAS) usage among lunar geopolymers, providing a material solution with high in-situ utilization, excellent mechanical properties, and robust durability for future lunar construction.

The cooperation of a pair of robot manipulators is required to manipulate a target object without any fixtures. The conventional control methods coordinate the end-effector pose of each manipulator with that of the other using their kinematics and joint coordinate measurements. Yet, the manipulators' inaccurate kinematics and joint coordinate measurements can cause significant pose synchronization errors in practice. This paper thus proposes an image-based visual servoing approach for enhancing the cooperation of a dual-arm manipulation system. On top of the classical control, the visual servoing controller lets each manipulator use its carried camera to measure the image features of the other's marker and adapt its end-effector pose with the counterpart on the move. Because visual measurements are robust to kinematic errors, the proposed control can reduce the end-effector pose synchronization errors and the fluctuations of the interaction forces of the pair of manipulators on the move. Theoretical analyses have rigorously proven the stability of the closed-loop system. Comparative experiments on real robots have substantiated the effectiveness of the proposed control.

The current paper deals with the effect of powder type and chemical admixtures on the rheological properties of mineral suspensions. The plastic viscosity of calcite, cement, and fly ash suspensions with or without superplasticizers (SP) and hydration retarders was characterized in a wide range of solid volume fractions. The results show that the plastic viscosity of suspensions increases with the decrease in particle size, and strongly decreases with the presence of superplasticizers. Besides, for reactive suspensions, hydration retarders decrease the plastic viscosity of the suspension, while competitive adsorption occurs when adding retarders to suspensions containing SP, leading to an increase in the plastic viscosity. Based on the experimental results, a relative plastic viscosity, i.e., the ratio between the total plastic viscosity and the theoretical viscosity contributed by the hard-sphere, is proposed to assess the effect of the contribution of colloidal forces. Moreover, the solid volume fraction of flocs in colloidal suspensions before percolation is identified by comparing the measured plastic viscosity with the Krieger-Dougherty model. Finally, a theoretical approach to determine the percolation packing fraction of minerals powders is further proposed.