The exploration of the Moon necessitates sustainable habitat construction. Establishing a permanent base on the Moon requires solutions for challenges such as transportation costs and logistics, driving the emphasis on In-Situ Resource Utilization (ISRU) techniques including Additive Manufacturing. Given the limited availability of regolith on Earth, researchers utilize simulants in laboratory studies to advance technologies essential for future Moon missions. Despite advancements, a comprehensive understanding of the fundamental properties and processing parameters of sintered lunar regolith still needs to be studied, demonstrating the need for further research. Here, we investigated the fundamental properties of lunar regolith simulant material with respect to the stereolithography-based AM process needed for the engineering design of complex items for lunar applications. Material and mechanical characterization of milled and sintered LHS-1 lunar regolith was done. Test specimens, based on ASTM standards, were fabricated from a 70 wt% (48.4 vol %) LHS-1 regolith simulant suspension and sintered up to 1150 degrees C. The compressive, tensile, and flexural strengths were (510.7 +/- 133.8) MPa, (8.0 +/- 0.9) MPa, and (200.3 +/- 49.3) MPa respectively, surpassing values reported in previous studies. These improved mechanical properties are attributed to suspension's powder loading, layer thickness, exposure time, and sintering temperature. A set of regolith physical and mechanical fundamental material properties was built based on laboratory evaluation and prepared for utilization, with the manufacturing of complex-shaped objects demonstrating the technology's capability for engineering design problems.

The solidification and molding of lunar regolith are essential for constructing lunar habitats. This study introduces an innovative lunar regolith molding technique that synergistically combines solar concentration, flexible optical fiber bundle energy transfer, and powder bed fusion. A functional prototype is developed to validate the proposed scheme. Systematic experiments including fixed beam spot melting, line melting, surface melting, and body melting are conducted using simulated basalt lunar regolith. Through in-situ observation of the melt pool's formation, evolution, and expansion dynamics, we identify a sequential transformation mechanism on the powder bed's surface: initial curling evolves into detachment from the bed, subsequent incorporation into a molten droplet, and ultimate solidification. A comprehensive evaluation of density and mechanical properties across multiple parameter combinations reveals that energy flux density of 3.33 MW/m2 with a scan speed of 30 mm/min, inter-track spacing of 3 mm, and layer thickness of 2 mm enables the production of structurally integral samples with continuous morphology. The resulting specimens demonstrate a maximum compressive strength of 4.25 MPa and a density of 2.31 g/cm3. This solar-powered additive manufacturing approach establishes a viable reference framework for large-scale on-site construction of lunar research stations.

Poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable polymer derived from fossil-based raw materials. Combined with poly(lactic acid) (PLA), a major material used in 3D printing, PBAT provides mechanical properties that are particularly attractive for applications requiring flexible 3D-printed objects. However, blends with high PBAT content in fused filament fabrication (FFF) are currently not well-documented, and optimal printing parameters remain unclear for advancing this field. This study aims to address this gap by first exploring the extrusion of filaments at different temperatures, followed by analyzing the printing conditions for PBAT/PLA blends to enhance their spectrum of applications. Using a commercial blend, Ecovio (R) (86 mol% PBAT), this paper demonstrates the feasibility of employing high PBAT content in the additive manufacturing process. Printing parameters such as nozzle temperature and speed were assessed based on the visual quality and mechanical properties of the specimens. The results indicate that extruding at 120 degrees C yields smoother filaments with adequate diameter for FFF applications. Regarding 3D-printing analysis, variations in parameters did not significantly impact elongation at break. However, increasing the nozzle temperature from 180 to 210 degrees C and the printing speed from 50 to 80 mm/s resulted in a 29% increase in tensile strength and a 77% increase in the modulus of elasticity of the 3D-printed specimens which is attributed to better interlayer adhesion. Therefore, high PBAT content blends can improve the performance of 3D-printed materials, and parameters must be optimized to exploit their effectiveness fully across various industrial uses.Highlights Extrusion temperature variations minimally affect PLA/PBAT thermal properties. Higher nozzle temperature and speed significantly improve mechanical properties. Optimal printing conditions for high PBAT blends enable flexible materials. PBAT blends show potential for enhanced 3D printing performance in all sectors.

Excavated soil from widescale tunneling and excavation can be used in 3D-printed constructions. This research investigates the feasibility of 3D printing using geopolymer stabilized excavated soil (GP-E) containing 42% clay rich in kaolinite minerals. At dosages 0.50-1.5 wt%, sucrose is added to control the hydration and timedependent rheological properties, enabling adequate open printing time (OPT) for large-scale printing. Experimental findings show that 1% and 1.5% sucrose addition to GP-E offers OPT of 130 min and 170 min respectively compared to 32 min for GP-E. By enabling better dispersion, the addition of sucrose allows smooth extrusion with shape retention of 90 - 92% at a lower NaOH solution-to-binder ratio (0.68) than GP-E (0.75). Sucrose and clay (in the soil) act synergistically to reduce the time-dependent static yield stress but maintain it at an adequate level of 5-8 kPa required for stacking up the layers without collapse. Flow retention and thixotropy are maintained at 100% during the printing window, which balances extrusion and buildability. As a result, the sucroseGP-E mix could be built up to a height of 1.05 m compared to 0.19 m for GP-E. 1 % sucrose-added GP-E possesses 28 - 40% and 70% higher wet compressive strength and inter-layer bonding respectively compared to GP-E depending on the loading direction. These are linked to the refinement of capillary porosity and a 13-15% reduction in shrinkage. In summary, the findings present a potential route for controlling the printing time of geopolymer-stabilized earthen materials while reducing the embodied carbon and enhancing the mechanical performance.

In-Situ Resource Utilisation (ISRU) is increasingly being seen as a viable and essential approach to constructing infrastructure for human habitation on the moon. Transporting materials and resources, from Earth to the Moon, is prohibitively expensive and not sustainable for long-term, large-scale development. Various fabrication technologies have been investigated in recent years, designed for extra-terrestrial exploration and settlement. This review presents a comprehensive study on the development of several sintering techniques of lunar regolith simulant to demonstrate its feasibility for ISRU on the moon. Various critical processing parameters are evaluated in pursuit of creating a structural material that can withstand the extreme lunar environment. Key outcomes are summarised and assessed to provide insight into their viability. Finally, current challenges are addressed and potential improvements, and avenues for further research, suggested.

Human space exploration missions in the near future will inevitably demand beyond-Earth manufacturing capacity to develop critical subsystems utilising in situ resources. Therefore, to find an alternative solution to the logistics challenges of long-duration space missions, an on-site component fabrication process utilising indigenous resources on the Moon and Mars will be economical and play a crucial role in ensuring the expansion of succeeding missions to deep space. Additive manufacturing (AM) exhibits excellent potential to develop intricate components with functional and tailorable properties at various scales. To assess the potential of AM, an artificial Mars soil has been processed to formulate stable aqueous paste containing less organics (1.5% versus typically 30-40%) amenable to resource-efficient 3D printing. The formulated paste was utilised to fabricate a range of solid and porous designs of various shapes and sizes using a layer-wise material extrusion method for the first time. The additively manufactured components sintered at 1100 degrees C for 2 h exhibited an average relative permittivity (epsilon r) = 4.43, dielectric loss (tan delta) = 0.0014, quality factor (Q x f) = 7710 GHz and TCf = - 9. This work not only demonstrates progress in paste additive manufacturing but also illustrates the potential to formulate eco-friendly ink that can deliver components with functional properties to support long-term space exploration utilising local resources available on Mars.

There is an increasing demand for sustainable construction materials to address the challenges posed by the environmental impact of the built environment (BE), which is driven by climate change, population growth, and urbanization. Conventional construction materials like cement contribute significantly to carbon emissions during production, transport, use, and disposal phases, and their poor thermal conductivity hinders efforts to maintain comfortable indoor environments. To address these challenges, there is an urgent need for innovative, locally sourced thermal insulation materials specifically designed for regions with extreme climates and high energy demands to maintain building comfort. This research explores synthesizing novel, environmentally friendly building materials using locally sourced date palm fiber waste and clay. The study also investigates the developed material's 3D printing (3DP) capabilities and optimizes its printing parameters with lab-scale prototypes. Additionally, thermo-mechanical characterization is conducted to assess its suitability for built environment applications. Different concentrations, from 1 to 5 wt% of date palm fiber to clay ratio (Dpf/C), were studied regarding microstructural, thermal, and mechanical properties, dimensional accuracy, and feasibility for 3DP of BE structures. Results demonstrated a significant reduction in thermal conductivity by 73%, achieving 0.244 W/mK, and an increase in compressive strength by 106%, reaching 10.9 MPa at 5 wt% Dpf/C. The promising thermomechanical properties of these composites and their suitability for 3DP support their use in real-world applications in the future's sustainable built environment. This scalable methodology can be adapted to regions with similar sustainable local and waste resources, advancing the circular economy.

In this research, we have successfully produced biodegradable composite filaments using Poly(butylene succinate) (PBS) and cocoa bean shell residues (CBS). These composite filaments, fabricated by incorporating up to 20 wt% of the natural filler into the PBS matrix through extrusion processing, have undergone rigorous rheological, mechanical, thermal, morphological, and soil disintegration characterizations. The results have unveiled the potential of printing biodegradable biocomposite filaments, with the materials demonstrating thermal stability in the printing process temperature range. However, a reduction in thermal stability was observed with the incorporation of the natural filler. Differential scanning calorimetry (DSC) analyses indicated a small crystallinity variation for the composites concerning the pure PBS matrix. Furthermore, incorporating the natural filler improved the disintegration rate in the composites' soil, suggesting that CBS can increase and modulate the biodegradation rate of the PBS matrix, thereby expanding its applications in sustainable packaging, 3D printed parts for consumer goods, and agriculture.Highlights Sustainable innovation by using PBS-CBS filaments for eco-conscious production. CBS boosts biodegradation and soil disintegration. Shaping a greener future with eco-friendly 3D printing of PBS-CBS biocomposites. Methodology for fabricating filaments with multiple processing cycles and their characterization. image

A multifunctional biodegradable additive powder has been created for simultaneous enhancement of toughness and compostability of the biopolymer poly(lactic acid) (PLA). PLA has promising strength and stiffness compared to commodity plastics, but the neat polymer is not a direct replacement for petroleum-based plastics in consumer products due to its brittle fracture and low ductility. Although officially certified as biodegradable, PLA suffers from a slow composting rate and is not considered compostable outside of specialized environments such as those found in industrial composters (where temperatures approaching 60 degrees C are used). A powder-based additive has been developed that increases both the elongation at break and the composting rate of PLA to enhance the attractiveness of PLA over current commodity plastics. In this study, various amounts of the additive are compounded into PLA using a single screw extruder. Test specimens are prepared using the additive manufacturing method of fused filament fabrication. The PLA-based composites show a minimal loss of strength and stiffness as compared to plasticized PLA resins, and the additives provide tunable properties to the material in the ability to control elongation versus strength and stiffness. Direct tensile testing of 3.75 mm filament for additive manufacturing to compare material properties is also investigated. The composting behavior is investigated using specimens made by extrusion as part of an additive manufacturing model system. Composting studies show an increase in composting rate under elevated temperature of 58 degrees C and 50 % relative humidity under modified ASTM D5338 soil contact testing. Microbial analysis indicates that the additive particles support the growth of specific degraders and shifts the composition of the microbial population of bacteria and fungi and has potential for enhancing the compostability in home compost.

This study investigates the potential of xanthan gum (XG) to serve as a biopolymer binder for improving the rheological, mechanical, and 3D printing properties of earth-based concrete, aligning with the pressing need for sustainable, low-carbon construction materials. Experimental results indicate that XG could disperse kaolinite clay particles, which likely arises from the highly negative charges of both kaolinite and XG. Rheological parameters display two trends with increasing XG concentration: initially decreasing yield stress, viscosity, and storage modulus owing to XG's dispersing effect, followed by an increase due to polymer overlapping. The same trend is observed in 3D printing experiments, where the kaolinite clay suspensions exhibited enhanced buildability with increasing XG concentration and eventually achieved a Printable state at 5 % XG. Additionally, compressive strength was observed to steadily increase with increasing XG content, for instance, nearly tenfold with 2.4 % XG compared to 0 % XG (0.34 MPa to 3.58 MPa). This exploration highlights the pivotal role of XG as a dual-functionality agent, acting as a robust binder and a promising rheology modifier.