Search Results (166)

Background: ExPEC9V was a 9-valent vaccine candidate intended for the prevention of invasive extraintestinal pathogenic Escherichia coli (ExPEC) disease (IED). Here, we describe more than a decade-long formulation development trajectory of this vaccine candidate aimed at establishing a stable, robust and scalable drug product that maintains long-term stability while addressing potential manufacturing challenges and increasing the probability of successful global deployment. Methods: Selected formulation development studies of the ExPEC multivalent vaccine candidate are summarized, spanning formulation screening, confirmation, and design of experiments (DoE)-based robustness, stability and compatibility studies. A formulation initially developed for an early low-valency vaccine candidate was subsequently tested and confirmed for candidates with additional serotypes incorporated based on antigen heterogeneity evidence. Contact materials employed included primary packaging—polycarbonate (PC) and polyethylene terephthalate glycol (PETG) bottles, borosilicate glass vials, stoppers, and prefilled syringes; vessel types—bags and stainless steel vessels used in drug substance (DS) and drug product (DP) manufacturing; and varying concentrations of tungsten and hydrogen peroxide. An evolving analytical panel was applied to assess attributes such as purity, protein concentration and degree of O-acetylation. Results: A phosphate-based formulation containing sorbitol, methionine, and polysorbate 80 showed superior stability in screening and was confirmed as fit for purpose across increasing vaccine valency. The ExPEC 9V drug product displayed remarkable thermal and formulation robustness, long-term (3 years) stability at 2–8 °C in glass vials and prefilled syringes, and compatibility with assessed primary containers and manufacturing materials. DoE-based robustness studies defined acceptable excipient and pH ranges, supporting a wide formulation design space. Conclusions: The development trajectory of the ExPEC9V vaccine candidate demonstrates that early prioritization of a robust, scalable formulation that remains fit for purpose across valency evolution supports a stable late-stage manufacturable drug product. Full article

Understanding the carbon emission characteristics of fused filament fabrication (FFF) is important for the development of more sustainable additive manufacturing practices. This study presents a framework for quantifying, modelling, and optimizing the carbon emissions of FFF-printed specimens of carbon-reinforced Polyethylene Terephthalate Glycol (PETG-CF) composite. Carbon emissions were assessed within a cradle-to-gate system boundary by considering material consumption and electrical energy usage during fabrication. The influence of print speed, raster angle, layer height, infill density and infill pattern on carbon emissions were experimentally investigated. Response Surface Methodology (RSM) was utilized to formulate a predictive carbon emission model, while analysis of variance was applied to assess the significance of the process parameters. The findings revealed that infill density, infill pattern, layer height, and raster angle significantly affected carbon emissions, while print speed showed a comparatively lower influence. Contour plot analysis was used to visualize parameter interactions and identify low-emission regions. RSM-based optimization predicted a minimum carbon emission of 0.0732 kgCO₂eq at a print speed of 220 mm/s, layer height of 0.12 mm, infill density of 50%, raster angle of 0°, and rectilinear infill pattern. The proposed framework presents a practical strategy for integrating carbon emissions for a sustainable FFF process. Full article

This study presents the design, fabrication, and experimental validation of the Hermes reusable model rocket platform integrating additive manufacturing, onboard sensing, and telemetry capabilities for low-cost aerospace experimentation. The rocket was manufactured using modular Polyethylene Terephthalate Glycol (PETG) components produced through fused filament fabrication to achieve a lightweight and structurally robust configuration suitable for repeated flight operations. A custom flight computer based on a Raspberry Pi Zero 2W was developed to acquire in-flight data from an inertial measurement unit, barometric pressure sensor, and Global Positioning System module, while an onboard camera enabled post-flight trajectory assessment. Aerodynamic performance and stability were evaluated using OpenRocket simulations, and propulsion was provided by a cluster of Klima D9-5 solid rocket motors. Four experimental flights were conducted to evaluate the integrated system architecture, assess telemetry and sensor performance, and compare experimental flight data with simulation predictions. The recorded measurements successfully captured the primary flight phases, including launch, ascent, apogee, descent, and recovery. The experimental results showed qualitative agreement with the simulated flight profiles; however, deviations in apogee altitude, acceleration, and flight duration were observed due to aerodynamic drag, environmental disturbances, motor-performance variability, and implementation-related limitations. The flight campaigns additionally identified practical challenges associated with wireless telemetry reliability, GPS signal acquisition, electronic protection, and parachute deployment, leading to iterative system improvements. From a sensing perspective, the flight campaigns demonstrate the operation and limitations of a low-cost embedded acquisition architecture under dynamic conditions, including the effects of sampling rate, sensor calibration, synchronization, wireless-link interruption, and local data preservation on the quality of the recorded flight measurements. The presented platform demonstrates the feasibility of combining low-cost additive manufacturing techniques with commercially available embedded electronics for reusable aerospace testing and educational applications. The proposed system further provides a flexible experimental framework for flight-data acquisition, simulation validation, and iterative development in academic and amateur rocketry research. Full article

Polyethylene Terephthalate Glycol (PETG) is a thermoplastic material used in Fused Deposition Modelling for prosthetic applications, where mechanical properties are strongly dependent on process parameters. This study investigated the effects of carbon fibre (CF) content, print orientation (PO), and print temperature (PT) on the mechanical performance of PETG, fabricated using a Bambu Lab A1 printer. Tensile, three-point bending and impact testing were conducted to characterise the mechanical response of printed specimens. A Taguchi L9 array was employed to evaluate parameter effects while minimising experimental runs, and factor effects were quantified using per-response general linear models. Findings indicated that PO and PT significantly affected tensile behaviour, while CF content dominated flexural stiffness and impact response, with the strongest tensile response at 240 °C attributed to improved interlayer bonding. CF reinforcement increased stiffness and flexural strength but had limited effect on tensile strength and a reduced impact resistance at higher loadings, indicating increased brittleness. PO was identified as the most influential factor, with upright specimens exhibiting superior tensile performance, consistent with more favourable alignment of filament deposition with the loading direction. These findings demonstrate that the mechanical behaviour of CF-PETG is strongly process-dependent, informing its future application within prosthetic limb design. Full article

The development of reusable and biocompatible biomaterial-based culture substrates is increasingly relevant for improving sustainability in biomedical research workflows. In this study, polyethylene terephthalate glycol-modified (PETG) was evaluated as a potential alternative to conventional polystyrene (PS) for in vitro cell culture applications. PETG substrates were fabricated through laser cutting and tested for their ability to support cell adhesion, viability, proliferation, and lineage-specific differentiation across multiple human cell models, including calvarial mesenchymal stromal cells (CMSCs), bone marrow-derived mesenchymal stromal cells (hBM-MSCs), dermal fibroblasts, LHCN-M2 myoblasts, and SH-SY5Y neuroblastoma cells. Morphological and immunofluorescence analyses demonstrated that PETG supported cell attachment and focal adhesion formation, comparable to standard PS surfaces. Cell viability and proliferation assays confirmed metabolic activity and growth over time. Furthermore, PETG substrates supported osteogenic, adipogenic, myogenic, and neuronal differentiation, as demonstrated by histological staining, myotube formation, neurite outgrowth, and lineage-specific gene expression analyses. Finally, PETG maintained CMSC morphology and metabolic activity after repeated recovery, ethanol/UV treatment, and gelatin re-coating, with comparable results between new substrates and those reused for up to three cycles. These findings support PETG as a biocompatible culture substrate with preliminary short-term reuse potential and possible sustainability benefits for laboratory workflows. Full article

To address the increasing demand for energy-efficient buildings, this study experimentally characterizes the effective (λ_eff) and apparent (λ_app) thermal conductivity of 3D-printed polymer plates. While 3D printing offers significant design flexibility, a lack of comprehensive comparative data between printable polymers and conventional building materials limits their integration into large-scale facade systems. This research investigates four distinct materials: standard polylactic acid (PLA Basic), foamable poly-L-lactic acid (PLA Aero), amorphous polyethylene terephthalate glycol (PETG), and carbon fiber-reinforced polyethylene terephthalate (PET-CF). Utilizing the guarded hot plate (GHP) method (ASTM C177, EN 12667, EN 12939), steady-state heat flux and temperature gradients were measured. The methodology incorporates a rigorous uncertainty analysis (k = 2) addressing the inherent inhomogeneity of additively manufactured components. Results demonstrate significant variations: PLA Aero achieved a 57.3% reduction in thermal conductivity (0.114 ± 0.005 W/(m·K)) compared to PLA Basic (0.267 ± 0.011 W/(m·K)), while PET-CF showed increased conductivity (0.533 ± 0.021 W/(m·K)) due to carbon fiber bridging. Notably, multi-layered PLA Aero assemblies outperformed conventional double-glazed units, reaching a minimum λ_app of 0.051 W/(m·K). These findings validate the GHP method for 3D-printed polymers and provide a technical foundation for material selection in next-generation, energy-efficient smart facades. Full article

The increasing demand for sustainable and lightweight furniture systems has driven interest in additively manufactured polymer components as alternatives to conventional metal hardware. However, their performance at the functional assembly level under standardized loading conditions remains insufficiently explored. This study evaluates the feasibility of replacing metal drawer slides with fused deposition modeling (FDM)-based polymer alternatives fabricated from polylactic acid (PLA) and polyethylene terephthalate glycol (PETG). Unlike previous studies focused on material-level characterization, this work investigates fully functional drawer slide assemblies integrated into medium-density fiberboard (MDF) systems, enabling component-level assessment under realistic conditions. Specimens were designed in SolidWorks and fabricated under controlled printing parameters. Commercial metal slides were used as benchmarks. Mechanical performance was tested according to BS EN standards, and deformation was measured at multiple points. Statistical analysis included ANOVA, Tukey HSD, and t-tests at a 95% confidence level. Results showed significant differences among materials (p < 0.05). Metal slides exhibited the highest stiffness and minimal deformation. PLA showed stable performance with minor surface degradation, while PETG demonstrated lower dimensional stability and premature failure due to higher compliance. Overall, PLA-based FDM components offer a cost-effective alternative for non-heavy-duty applications, whereas PETG requires further optimization. The study bridges additive manufacturing and real-world furniture component performance under standardized testing. Full article

Despite major advances in polymer composites for Fused Filament Fabrication (FFF), designing environmentally sustainable materials from bio-based resources remains a key research priority. The objective of this study is to check the processability and properties of sustainable PETG/cork composites processed via FFF technology. Filaments with 5 and 10% of cork were created using a twin-screw extruder. Samples from these filaments were printed by FFF technology, and subsequently subjected to morphological, thermal and mechanical testing. As a result of the study, it was proved that the 3D-printing process did not result in a tensile strength decrease with an increasing cork percentage, as observed in mechanical testing of the filament. The addition of cork significantly increased plasticity without decreasing tensile strength when introducing 10% of cork particles. The interfacial temperatures of the prepared composites did not differ much from the polymer matrix and were 79.55 °C, 77.56 °C, 76.67 °C for PET-G, PET-G + 5% cork, and PET-G + 10% cork, respectively. Thermal conductivity decreased significantly as the percentage of cork increased. This work shows that FFF technology is one of the most suitable manufacturing options for PETG + 10% cork composites to produce things with low conductivity and the same thermal and mechanical properties as pure PETG. Full article

The presence of polymeric impurities in recycled polyethylene terephthalate (PET) streams, particularly amorphous copolyesters such as polyethylene terephthalate glycol-modified (PETG) and polycyclohexylenedimethylene terephthalate glycol-modified (PCTG), as well as polycarbonate (PC), represents a critical challenge for high-performance applications involving orientation drawing. In this study, the influence of such components on the orientation behavior and resulting mechanical properties of PET-based blends was systematically investigated. Model blends were prepared using virgin materials and processed into monofilaments via inline melt spinning followed by controlled orientation drawing with draw ratios up to 6.5. The evolution of tensile strength, modulus, elongation at break, density, and thermal shrinkage was analyzed as a function of draw ratio. The results demonstrate that PET-rich systems exhibit superior mechanical performance, which is consistent with the development of strain-induced crystallization during orientation drawing, reflected in increased density and reduced thermal shrinkage at higher draw ratios. In contrast, amorphous copolyesters (PETG, PCTG) suppress crystallization, resulting in limited structural development, lower modulus, and significantly higher thermal shrinkage. Blends containing polycarbonate showed reduced maximum draw ratios and tensile strength, indicating restricted orientation capability, but exhibited comparatively low shrinkage at moderate draw levels. The study establishes clear structure–property relationships linking molecular orientation, crystallization behavior, and macroscopic performance in PET-based blends. The findings highlight that even minor amounts (~10 wt%) of amorphous polyester impurities can significantly alter orientation efficiency and end-use properties, emphasizing the importance of feedstock control in recycling processes targeting high-performance-oriented products such as strapping tapes and monofilaments. Full article

Sustainable production in dental and orthodontic 3D printing has gained increasing attention due to environmental concerns and the need for cost-effective and resource-saving solutions. This study presents a proof of concept for using recycled polymers and fused granular fabrication (FGF) in a closed-loop 3D printing approach, omitting intermediate filament manufacturing. A desktop 3D printer served as the kinematic platform and was modified with a pellet-based extruder to directly process recycled polyethylene terephthalate glycol (PETG) flakes, obtained by shredding previously printed PETG parts, into dental models. Dimensional accuracy was evaluated using optical 3D scanning analysis. The results indicate that models produced from recycled PETG are, in principle, suitable for dental and orthodontic applications within the investigated scope. This technical note provides initial evidence supporting the integration of recycled thermoplastics into dental and orthodontic model fabrication as part of sustainable additive manufacturing workflows. Potential pathways for workflow integration in clinical and laboratory environments, as well as directions for future research, are outlined, including the optimization of printing parameters and process stability. The main technical challenges were unreliable feedstock flow, causing bridging and jamming, while thermal creep from insufficient inlet cooling promoted premature softening of the flakes, causing torque spikes and unstable feeding. Full article

This paper presents the results of research conducted on the influence of thermoplastic extrusion parameters (layer height per pass—L_h and the percentage fill density—I_d) and heat treatment (annealing) on the compressive strength of specimens manufactured by thermoplastic extrusion of virgin and recycled polyethylene terephthalate glycol (PETG and rPETG) filaments. To support the study, using the parameters L_h = (0.10–0.20) mm and I_d = (50–100)%, 90 compression test specimens were manufactured from PETG and rPETG (45 specimens for each material), which were subsequently subjected to heat treatment by annealing at a temperature of 75 °C for a period of 180 min. The results obtained highlight a significant correlation between the variable manufacturing parameters (L_h and I_d) and the compressive strengths (C_s). The average compressive strengths of the 45 specimens made from PETG are 44.15% lower than the average compressive strengths of the specimens made from rPETG. The annealing heat treatment resulted in a 31.40% decrease in the average compressive strengths of the specimens made from PETG and a 0.63% increase in the average compressive strengths of the specimens made from rPETG. The specimens made from PETG exhibited increased thermal sensitivity, which led to molecular relaxation, while rPETG exhibited superior thermal stability acquired through recycling. Full article

Adhesion between fused deposition modelling (FDM) printed polymers and textile substrates is critical for durable printed-on-textile hybrids. Since no dedicated test standard exists for additively manufactured textile interfaces, many studies use T-peel methods adapted from adhesive-bond standards. However, printed-on-textile joints are often governed by polymer penetration into the fabric and mechanical interlocking, rather than by a discrete adhesive layer. This work evaluates a fixture-based perpendicular (normal-separation) tensile method, using a circular dolly printed directly onto a cotton plain-weave substrate and a fully 3D-printable, threaded, self-aligning clamping assembly. Three representative filaments, namely polyethylene terephthalate glycol-modified (PETG), polylactic acid (PLA), and thermoplastic polyurethane (TPU), were tested using both the proposed pull-off method and an ISO 11339-type T-peel benchmark, with n = 8 specimens per polymer. The perpendicular method produced complete datasets for all polymers and clearly differentiated adhesion performance (TPU > PLA > PETG). In contrast, for T-peel, the standard evaluation window (25–125 mm) was completed for all PETG specimens but only for a subset of PLA specimens and a single TPU specimen. In the remaining tests, premature substrate failure prevented completion of this window, so the results could not be evaluated. Microscopy confirmed distinct interlocking morphologies across polymers, supporting the observed differences in failure behavior between peel and normal separation. Overall, the results indicate that perpendicular dolly pull-off testing is a practical and reproducible alternative for quantifying adhesion across a wider range of printed-on-textile bonding conditions. Full article

This research systematically investigates the shape memory properties of re-entrant hexagonal negative Poisson’s ratio (NPR) honeycomb structures fabricated via 4D printing, using polyethylene terephthalate glycol (PETG) and polylactic acid (PLA) as comparative materials. Periodic honeycomb models with varied wall thicknesses and structural unit angles were designed, and their effects on shape recovery time and recovery rate were examined. Response surface methodology (RSM) based on a Box–Behnken design was employed to optimize key process parameters, including the wall thickness, structural unit angle, and mold pressing angle. The results demonstrate that PETG exhibits significantly superior shape memory performance compared to PLA, characterized by a shorter recovery time and higher recovery rate under thermal stimulation. Through RSM optimization, the optimal parameter combination was identified as a wall thickness of 0.5 mm, a structural unit angle of 65°, and a mold pressing angle of 135°, which was subsequently validated experimentally, demonstrating a high degree of consistency between predicted and actual outcomes. This study not only clarifies the influence of the structural parameters on the shape memory behavior of NPR honeycomb systems but also provides parameter guidance and a practical experimental basis for the application of PETG in 4D-printed intelligent structures, with potential implications for soft robotics, aerospace, and biomedical devices. Full article

Three-dimensional printed polymers produced using Fused Deposition Modelling (FDM) exhibit directional microstructures resulting from filament paths, layer interfaces, and cellular infill, leading to mechanical and tribological responses distinct from those of homogeneous bulk materials. This study presents a comparative tribomechanical evaluation of polypropylene (PP) bulk inserts and 3D-printed polyethylene terephthalate glycol (PETG) inserts with a 30% hexagonal infill, relevant for robotic gripping applications. Progressive scratch tests were performed under loads from 5 to 100 N (150 N for PP), and profilometry was applied to quantify groove morphology, ridge formation, and displaced-volume ratios. An elasto-plastic conical indentation model was used to derive indentation pressures and elastic–plastic transition radii from groove geometry. The PETG inserts exhibited heterogeneous groove depth, intermittent ridge tearing, and friction fluctuations associated with the internal infill structure, consistent with previous findings on anisotropy and architecture-dependent behaviour in additively manufactured polymers. In contrast, bulk PP demonstrated smoother friction profiles and more stable plastic flow under increasing loads. Two functional indices—specific frictional work and ridge-to-trace volumetric ratio—are introduced to support material selection for robotic gripping systems. The results show that local contact mechanics in 3D-printed inserts are governed by print-induced structural features and can be effectively evaluated through a scratch-based elasto-plastic analysis. The methods and results presented in this work support the rational selection and design of polymer inserts for robotic gripper fingertips. The proposed scratch-based elasto-plastic evaluation framework enables manufacturers and automation engineers to compare 3D-printed and conventional materials based on friction stability, wear response, and deformation resistance. This approach can be directly applied to optimise gripping performance in industrial handling, packaging, and collaborative robotics. Full article

The conducted study was focused on the development of a new type of polymer blends intended for additive manufacturing applications, in particular, the material extrusion method (MEX). The developed materials were prepared from recycled poly(ethylene terephthalate) and amorphous copolymers poly(ethylene terephthalate-glycol) (PETG), and poly(cyclohexylenedimethyl terephthalate-glycol) (PCTG). The basic blend systems were additionally modified with POE-g-GMA impact modifier (IM) during the reactive extrusion process. The main aim of the work was to assess the effectiveness of using composite additives and their influence on the mechanical and thermomechanical parameters of the tested systems. To prepare the composites, selected polymer blends were modified with 10% of talc (T) and carbon fibers (CF). The properties evaluation includes the mechanical/thermomechanical testing, thermal analysis and structural observations. The accuracy of printing was measured using optical scanning methods. The test results indicate that even the relatively small amount of the CF filler could lead to a significant increase in tensile modulus from reference 1.6 GPa to 2.9 GPa; the same improvement applies to strength values, where the CF-modified materials reached 45 MPa, compared to the reference 31 MPa. The heat deflection tests (0.455 MPa) after annealing revealed the maximum HDT of around 170 °C for both types of CF-modified materials. The Vicat test results were also favorable for annealed materials. Considering that the Vicat/HDT results after the 3D-printing process usually reach around 70 °C, the performed heat treatment strongly enhanced the heat resistance for most of the prepared blends. The performed studies revealed that for most of the prepared materials, the brittleness was a common drawback for both MEX-printed and injection-molded materials. Full article