Three-dimensional printing technologies are transforming various sectors with promising technological abilities and economic outcomes. For instance, 3D-printed concrete (3DPC) is revolutionizing the construction sector with a promise to cut projects’ costs and time. Therefore, 3DPC has been subjected to extensive research and development to optimize the mechanical and thermal performance of concrete walls produced by 3D printing. In this paper, we conduct a comparative investigation of the thermal performance of various infill structures of 3DPC walls. The targeted outcome is to produce an infill structure with optimized thermal performance to reduce building energy consumption without incurring additional material costs. Accordingly, a computational model is developed to simulate the thermal behavior of various infill structures that can be used for 3DPC walls. The concrete composition and the concrete-to-void fraction are maintained constant to focus on the impact of the infill structure (geometric variations). The thermal performance and energy-saving potential of the 3DPC walls are compared with conventional construction materials, including clay and concrete bricks. The results show that changing the infill structure of the 3DPC walls influences the walls’ thermal conductivity and, thereby, the building’s thermal performance. The thermal conductivity of the examined infill structures is found to vary between 0.122 to 0.17 W/m.K, while if these structures are successful in replacing conventional building materials, the minimum annual saving in energy cost will be about $1/m². Therefore, selecting an infill structure can be essential for reducing building energy consumption.

Scaffold architecture plays a significant role in regulating cellular and microbial interactions in tissue engineering applications. This study evaluates the performance of 3D-printed poly (lactic acid) (PLA) scaffolds with varying porosity levels (20%, 40%, 60%, 80%, and 100%) in mechanical strength, supporting human skin fibroblast (HSF) viability and reducing bacterial colonization of Gram-positive bacteria (Staphylococcus epidermidis, Staphylococcus aureus), and Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli). The maximum tensile strength (28 MPa) was achieved in the 100% dense scaffold. Increasing porosity drastically decreased tensile strength, where 80% PLA scaffold possessed 16 MPa strength. At greater levels of porosity (60% and 40%), tensile strengths greatly decrease (8 MPa and 4 MPa), while ductility increases, especially at high porosity levels. HSF viability, assessed using the AlamarBlue assay, showed a time-dependent increase in cell proliferation, with the highest viability observed on scaffolds with 60% and 80% porosity. SEM imaging confirmed strong cell adhesion on the 80% porous scaffold, indicating that intermediate-to-high porosity enhances cell attachment and metabolic activity. In contrast, bacterial adhesion showed species-specific responses to scaffold porosity. S. epidermidis and E. coli exhibited a progressive increase in adherence with porosity, peaking at 100%. P. aeruginosa showed maximum adhesion at 80%, suggesting a porosity “sweet spot” that favors its colonization. S. aureus adhered most strongly to scaffolds with intermediate porosities (40–60%) and significantly less at 100% porosity. The current study provides insights into scaffold design considerations, emphasizing the need for optimized scaffold architecture that balances regenerative potential with infection control in tissue engineering applications.

Polyethylene terephthalate glycol (PETG) is a versatile thermoplastic widely used in food packaging and biomedical applications owing to its excellent mechanical properties, chemical resistance, biocompatibility, and ease of processing. Porosity is a critical design parameter that governs the biological and mechanical performance of 3D-printed PETG structures by influencing cell attachment, nutrient transport, mechanical integrity, and microbial interactions. In this study, PETG scaffolds were fabricated at five nominal infill densities (20%, 40%, 60%, 80%, and 100%) using fused deposition modelling (FDM) to investigate the influence of printing-defined architecture on mechanical performance and bacterial colonization. Tensile testing revealed that decreasing infill density resulted in a progressive reduction in ultimate tensile strength and Young’s modulus, demonstrating the trade-off between reduced material density and mechanical integrity. Bacterial interactions with the scaffolds were evaluated against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, and Salmonella typhimurium using optical density (OD) and ATP-based viability assays to quantify both planktonic and adherent bacterial populations. The results demonstrated that the influence of scaffold porosity was species-dependent. The results demonstrated species-dependent responses to scaffold architecture. Higher infill densities were generally associated with reduced attachment and metabolic activity for P. aeruginosa, S. epidermidis, and S. typhimurium, whereas E. coli exhibited relatively stable growth and metabolic activity across the tested infill conditions. S. aureus showed an intermediate response, with bacterial attachment and metabolic activity varying according to scaffold architecture. Overall, infill density exerted a greater influence on scaffold-associated bacteria than on planktonic populations, while simultaneously determining the mechanical performance of the printed structures. These findings demonstrate that controlling PETG infill architecture is important for balancing mechanical properties and bacterial colonization and provide design insights for future PETG-based biomedical and food-packaging applications.