Lunar soil-based polymers, created using lunar soil as a precursor combined with highly automated 3D printing construction methods, hold great potential for lunar base construction. However, technical challenges such as ambiguities in characterizing rheological behavior and difficulties in regulation limit their 3D printing workability. To address these issues, the applicability of the Bingham model, Herschel-Bulkley (H-B) model, and a modified Bingham model to TJ-1 simulated lunar soil-based polymer was investigated by analyzing the fluidity variation. The effects of the solid-liquid ratio, Ca(OH)2, and Hydroxypropyl Methyl Cellulose ether (HPMC) on the 3D printing performance of the simulated lunar soil-based polymer were explored through one-way tests and standard deviation analysis. The results show that the modified Bingham model more accurately describes the rheological properties of TJ-1 simulated lunar soil-based polymer. HPMC proved to be an effective thixotropic agent for adjusting the 3D printing performance of the polymer. The yield stress and plastic viscosity of the polymer doped with 0.15 % HPMC were 3.577 Pa and 0.733 Pa s, respectively, meeting the requirements for printability. The yield stress and plastic viscosity of the simulated lunar soil polymers ranged from 1.84 to 3.58 Pa and 0.23-0.73 Pa s, respectively. Moreover, the compressive and flexural strengths of the simulated lunar soil polymers were significantly improved by adding Ca(OH)2. The optimal ratios for 3Dprinted simulated lunar soil polymers are a water-cement ratio of 0.30, 10 % NaOH, 8 % Na2SiO3, 6 % Ca(OH)2, and 0.10 % HPMC. Under these conditions, the 28-day compressive strength and flexural strength were 19.5 MPa and 6.9 MPa, respectively, meeting the strength standards of ordinary sintered bricks.The research results could provide a theoretical basis for the subsequent optimization of the simulated lunar soil base polymer mixing ratios for 3D printing.

The construction industry faces significant challenges, including the urgent need to minimize environmental impact and develop more efficient building methods. Additive manufacturing, commonly known as 3D-printing, has emerged as a promising solution due to its advantages, such as rapid fabrication, design flexibility, cost reduction, and enhanced safety. This technology enables the creation of structures from digital models through automated layering, presenting opportunities for mass production with innovative materials and architectural designs. This article focuses on developing eco-friendly earthen-based materials stabilized with 9 % cement and 2 % rice husk (RH) for large-scale 3D-printed construction. The raw materials were characterized using geotechnical tests for soil, water absorption tests for natural fibers, and SEM-EDS to examine their microstructure and elemental composition. Key properties such as rheology, printability (pumpability and extrudability), buildability, and compressive strength were evaluated to ensure the material's optimal performance in both fresh and hardened states. By utilizing locally sourced materials such as soil and rice husk, the mixture significantly reduces environmental impact and production costs, making it a sustainable alternative for large-scale 3D-printed construction. The material was integrated into architectural and digital fabrication techniques to construct a bioinspired housing prototype showcases the practical application of the developed material, demonstrating its scalability, adaptability, and suitability for innovative and costeffective real housing solutions. The article highlights the feasibility of using earthen-based materials for sustainable 3D-printed housing, thereby opening new possibilities for advancing greener construction practices in the future.

Imagine a world in which architecture will be 3D printed from living materials. That buildings will germinate, bloom, wither, produce new kinds of materials, and return back to the soil. This article introduces an innovative approach to sustainable architecture, through the utilization of 3D-printed structures crafted from locally sourced soil and plant seeds. After printing, the seeds germinate over time, forming load-bearing designs with interwoven root systems, which exhibit remarkable strength and resilience, reducing reliance on conventional construction materials. The research evaluates the mechanical properties of 3D-printed living structures through a set of material experiments to find a material combination that will allow maximum growth within 3D-printed architectural scale objects. The successful pilot project demonstrated their strength and capacity to support plant growth. The study also addresses the esthetic, cultural, and social dimensions of this novel fabrication technique, offering personalized, native plant-based patterns, and fostering community engagement. In conclusion, this research underscores the transformative potential of 3D-printed root-built structures as a sustainable architectural solution. By harnessing local soil and plant roots, these living constructions offer an eco-friendly alternative to conventional materials, with diverse environmental and social benefits. This study contributes to the evolving knowledge base of eco-conscious building practices, encouraging further exploration and adoption of nature-based solutions in architecture. With ongoing development, root-built buildings hold the promise of revolutionizing design, construction, and habitation, promoting a harmonious coexistence between humans and the natural environment.

Preparing regolith-based composites for 3D printing is crucial in lunar base construction, leveraging costeffective and mechanically favorable materials for lunar construction by utilizing lunar regolith as the reinforcing phase. This research focuses on developing lunar regolith simulant as a matrix for 3D printing, which is crucial for in-situ resource utilization on the Moon. Resin-based composites, well-established in aerospace, are explored for their simple manufacturing and robust properties. The formulation involves simulated regolithbased polymer for direct ink writing printing. Rheological properties, including yield stress and plastic viscosity, are characterized across various cementite-sand ratios and printing temperatures. The relationship between extrudability, the time interval of the printing material and its rheological attributes is investigated. Quantitative assessment of material buildability employs three-dimensional scanning of the printed parts. Freeze-thaw cycle tests explore its temperature resilience. The influence of varying the printing infill rate on printing efficiency and the performance of the printed parts was assessed. It was found that modulating the printing infill rate affects the efficiency and performance of parts, with a 1:4 cementite-sand ratio and a 40 degrees C print temperature demonstrating optimal printing workability. These findings offer an efficient scheme for the automated production of regolithbased epoxy composites with precise structural, temperature-resistant, and favorable mechanical properties.

The escalating global crisis of plastic waste necessitates innovative and sustainable approaches to its management. This study explores a novel method; the transformation of discarded plastic materials into high quality 3D printing filaments, offering a promising solution to this pervasive environmental challenge. This review paper delves into the prospects of leveraging plastic waste recycling for the production of 3D printing filaments, thereby advancing the cause of sustainable additive manufacturing. The investigation encompasses a comprehensive examination of the recycling process, encompassing waste collection, sorting, and filament extrusion. The outcomes of this study underscore the substantial potential of recycling plastic waste for 3D printing filaments as a sustainable alternative to conventional manufacturing. This review also delves into the polymer degradation phenomenon, assessment of properties of recycled polymers, and environmental impact assessment, conducting a comparative analysis with traditional filament production methods. This paper advances the application of recycling plastic waste for 3D printing filaments, offering a tangible and immediate response to the global plastic waste crisis.

Geocells have become an integral part of many geosystems like road and railway embankments, retaining walls and foundations, attributed to their multiple merits in terms of stability and strength, but their contributions towards liquefaction mitigation are unknown. The present study aims to understand the role of geocell reinforcement on the liquefaction and post-liquefaction shear response of saturated sands through monotonic and cyclic triaxial tests. Low-strength geocells of required physical and mechanical properties were fabricated through ultrasonic welding of 3D printed polypropylene (PP) sheets. The liquefaction benefits of including a single geocell in sand were quantified in terms of the reduction in pore water pressure, retardation in stiffness degradation and delay in the retardation of effective stress. In general, the inclusion of geocells delayed liquefaction, with higher beneficial effects at lower initial confining pressure, higher cyclic strain amplitude and higher cyclic loading frequency. The maximum benefit measured in terms of percentage rise in the number of cycles needed to liquefy was calculated to be about 230 %. Geocell reinforcement also helped in the quick regain of post-liquefaction shear strength and stiffness.

Understanding the interface shear behavior between clay and structures is crucial in geotechnical engineering. The mechanism of the roughness effect in the shear process between the clay and structures was studied to reveal the macroscopic and microscopic interface shear behavior. The different surface protrusion shapes of the structures were produced using a three-dimensional (3D) printer. Direct shear tests were conducted to analyze the shear failure modes and peak and residual strengths under different conditions. Subsequently, a discrete element method (DEM) numerical analysis was employed to study the contact network, soil fabric evolution, shear zone, coordination number, and void ratio variations in the interface shear. The test results indicated that the shear interfaces exhibited the same failure mode under various conditions, and the peak and residual strengths showed a strong positive correlation with roughness. The results obtained from numerical calculations match the experimental findings. The contact orientations and principal stresses shifted during the shear process, and the shear zone, coordination number, and void ratio also showed regular changes with the change of roughness. The evolution of microscopic parameters in DEM can effectively help explain the macroscopic interface shear behavior.

In the vat photopolymerization (VPP) 3D printing of ceramic cores, the solid loading is generally conducive to the microstructure and performance of products, owing to the improved bonding between adjacent layers and enhanced dimensional accuracy with increasing solid loading. In this work, the content of ceramic powder in photosensitive resin was optimized, the solid loading increased from 56 vol% to 68 vol%, and a novel curing model was established to explain the impact of solid loading on the printing precision. During sintering, the shrinkage is regulated to approximately 3 %, demonstrating a more homogeneous structure. The interlayer strength increased to 11.43 MPa while maintaining an apparent porosity of 23.47 %. Furthermore, the anisotropy of VPP-3D printed ceramic cores dependent on the solid loading was investigated. The ratio of vertical strength to horizontal strength (sigma V/sigma H) increased from 0.57 to 0.68 when the solid loading grew from 56 vol% to 68 vol%. At 1540 degrees C, the value of sigma V/sigma H was further enhanced to 0.81. This value met the precision casting criteria for ceramic cores effectively. This work can provide a reference for the investigation of high-solid-loading ceramic cores.

To improve the formability and bonding strength of 3D printing soil, a temperature-stimulating responsive intelligent soil-hydrogel 3D printing formula was innovatively developed by combining soil and gelatin. Varied soil-gelatin composites, featuring different gelatin content by weight of soil (0 %, 0.5 %, 1 %, and 1.5 %), were prepared and cured at 5 degrees C to facilitate the crosslinking of gelatin. An array of tests, including rheological assessments, compressive tests, and scanning electron microscopy analysis. Were conducted to thoroughly characterize the performance of gelatin-soil composites for 3D printing. Our findings unveiled that, following the cross-linking of gelatin at 5 degrees C, the gelatin-soil composites exhibited superior formability and bond strength compared to the reference. Furthermore, the soil-gelatin composites demonstrated not only comparable compressive strength to the reference but also enhanced interlayer bond strength. This innovative soil-hydrogel 3D printing formula, combining the versatility of soil and the responsive characteristics of gelatin, presents a promising avenue for advancing the capabilities of 3D printed soil.

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.