Search Results (414)

Three-dimensional (3D) bioprinting provides new options for airway reconstruction by enabling the fabrication of customizable, biodegradable scaffolds designed to support in situ tissue regeneration. Building on our established large-animal platform, in which two cm bioprinted tracheal grafts combined with refined surgical techniques and adjunctive laser intervention have achieved long-term survival exceeding three months, the present study aims to explore long-segment (≥four cm) tracheal transplantation. We evaluated the fabrication feasibility and regeneration patterns of extrusion-based 3D bioprinted polycaprolactone (PCL) tracheal grafts in a porcine model. The grafts were implanted via end-to-end anastomosis with adjunctive mechanical stabilization and followed by serial bronchoscopic surveillance, gross examination, and histological analysis. The two cm PCL tracheal grafts achieved reproducible survival exceeding three months when combined with refined surgical techniques, structured postoperative airway management, and optimized wound coverage. Histological analysis revealed multi-lineage tissue formation—including cartilage, muscle, glands, and epithelium—was observed. Cartilage regeneration followed a staged maturation process, compared to epithelial regeneration, although continuous by 12 weeks, remained developmentally immature. A single long-segment transplantation was explored in a single preliminary case, providing an initial technical observation of feasibility; however, definitive conclusions regarding long-term survival or regeneration cannot be drawn. These findings further characterize regenerative responses in a large-animal model and highlight critical translational barriers—fabrication constraints, airway biomechanics, and delayed epithelial maturation—that require systematic investigation before long-segment tracheal reconstruction can advance toward clinical application. Full article

The performance of flux-cored Zn-Al filler metal is susceptible to corrosion-induced degradation, thereby impairing its brazability. In this study, flux-cored Zn-2Al filler metals are prepared, and the salt spray test is subsequently carried out on the prepared filler metals. Scanning transmission electron microscope is used to identify the phases in filler metals. An electrochemical workstation was employed to test the electrochemical performance of the filler metals. The corrosion pathways and evolution patterns of filler metals are analyzed. The findings demonstrate that the corrosion type of the filler metals is electrochemical corrosion, characterized primarily by the corrosion modes of pitting corrosion and intergranular corrosion. The cathode is the α-Al phase, which undergoes an oxygen-absorption corrosion reaction, while the anode is the η-Zn phase, which experiences corrosion and subsequent dissolution. The continuously distributed α-Al phase bands and discontinuously distributed large-sized rod-like α-Al phases accelerate the corrosion rate, and the corrosion propagation rate along the extrusion direction is higher than that in the radially inward direction. After 15 days of salt spray corrosion, the tensile strength of filler metals decreases by 16.2%, and the elongation rate decreases to 3.73%. Full article

Understanding embryonic development is fundamental to improving captive breeding protocols and supporting conservation strategies for threatened fish species. Prochilodus vimboides is a Neotropical freshwater fish for which detailed information on early ontogeny remains scarce. This study aimed to characterize the embryonic and early larval development of P. vimboides under captive conditions. Broodstock were hormonally induced to reproduce, and extrusion occurred between 209 and 230 degree-hours after induction at 21.49 ± 0.15 °C. Embryonic development was monitored at regular intervals after fertilization (AF) using freshly collected eggs examined under a stereomicroscope. The principal developmental stages were identified, namely zygote, cleavage, including morula and blastula, gastrula, organogenesis, and hatching. Fertilized oocytes exhibited marked hydration and formation of a large perivitelline space at 15 min AF. More than 50% of embryos reached the two-blastomere stage by 20 min AF, and cleavage continued until 2 h 14 min AF. The gastrula stage was observed at 3 h 23 min AF, blastopore closure occurred at 11 h 47 min AF, and organogenesis began at 12 h 55 min AF. Complete hatching occurred at 22 h 04 min AF, and larvae subsequently initiated yolk sac absorption without cannibalistic behavior. These findings provide a species-specific developmental framework that supports captive production and conservation efforts for P. vimboides in the Paraíba do Sul River Basin. Full article

Currently, the packaging sector must continue developing more sustainable systems to reduce the high quantities of single-use plastic waste generated. This study evaluated the production and characterization of bio-based composite trays with antimicrobial activity. Different formulations of polybutylene adipate co-terephthalate (PBAT) and polylactic acid (PLA) with polyethylene glycol (PEG) as plasticizer and citric acid as a compatibilizer/crosslinker were evaluated, in addition to the inclusion of plantain microfibers (PFs), TiO₂, and menthol as reinforcing and antimicrobial agents, respectively. The mixtures were subjected to pellet extrusion (165/175/185/190 °C and 60 rpm) and then to flat sheet extrusion (at 185/190/195/205 °C and 60 rpm), besides calendering (at 3.5–6.0 rpm). A single-screw extruder was used in both cases. The obtained sheets (0.317 ± 0.040 mm thick and 17 cm wide) were molded into 12.5 × 11.0 × 3.5 cm trays in a thermoforming machine (at 325 °C and vacuum pressure). For the resulting composite sheets and trays, measurements of mechanical strength, moisture absorption, barrier (WVTR), transmittance, and color were performed. FT-IR, DSC, TGA, SEM, and in vitro antimicrobial tests were also conducted. Based on these tests, an initial formulation with an 85/15 (w/w) PLA/PBAT ratio was defined, which was then reinforced with 3% (w/w) PF. Furthermore, the inclusion of 5% (w/w) menthol in the composite led to fungistatic activity against Botrytis cinerea, also resulting in homogeneous sheets (tensile strength 24.137 ± 1.439 MPa) and trays (compressive strength 0.113 ± 0.010 MPa). These findings can be applied to the packaging and preservation of perishable produce. Full article

3D printing (3DP) of cement-based systems (CBSs) is a highly demanded technology in the construction field. Material requirements include specific rheological conditions for proper extrusion, followed by fast stiffening and strength gain to allow the construction process to continue, taking into account variable environmental conditions if the construction is on-site. To guarantee quality control of the process, it is essential to define field-oriented testing methodologies that allow real-time monitoring of mechanical properties’ evolution of the printed material, which will govern construction speed. This study evaluates the cone penetration test (CPT) method as a field-oriented test method to estimate the mechanical properties of 3DP CBSs over time. CPT penetration depth measurements were used to calculate shear yield stress and fresh compressive strength over time for 90 min. The experimental results were compared to two widely used laboratory tests: the fresh compressive strength test (squeeze test—SQT) and DSR test (vane test—VT). CBS pastes with and without fly ash and with three inorganic modifiers (nanoclays) and two types of organic rheology-modifying admixtures were considered. The results showed that CPT is highly conditioned by the stiffness of the paste, measured by the compressive Young Modulus (E), overestimating CBSs’ strength. The increase in E over time showed an inflection point at 130 kPa, corresponding to the evolution from plastic to pseudo-rigid behavior in the pastes. The corresponding time was used to define a linear adjustment for the average strength calculated using the CPT regarding both the fresh compressive SQT and shear yield stress VT. Full article

High-moisture extrusion (HME) is critical for plant-based meat analogs with meat-like fibrous structures. To expand HME protein sources, this study explored mung bean protein (MBP) substitution (0–50%, dry basis) effects on structural, textural and functional properties of soy protein concentrate (SPC)–wheat gluten (WG) HME products. At 20% MBP addition, the proteins formed a dense layered fibrous network, and the fibrous degree of the extrudates reached the peak. MBP > 40% disrupted the continuous protein network. The optimal rehydration for 20% MBP dried extrudates was 60 °C for 40 min, preserving fibrous texture. Protein interaction analysis indicated that hydrogen bonds and disulfide bonds played an important role in stabilizing the protein network structure. Overall, MBP can be incorporated into SPC-WG-based HME products to diversify protein sources, providing a feasible strategy for developing high-quality, nutritionally diversified plant-based meats. Full article

Heat creep is a critical failure mechanism in fused filament fabrication (FFF) extrusion systems, arising from insufficient thermal isolation between the hot end and cold end. It causes premature polymer softening, extrusion instability, and nozzle clogging, especially when active cooling is reduced or lost. This study experimentally evaluates passive cooling strategies for mitigating heat creep in consumer-class printers by exploiting ambient thermal stratification within the build volume. Vertical air-temperature gradients above heated build plates were measured for enclosed, semi-enclosed, and open-frame architectures, revealing pronounced stratification. Cold-end temperatures were then quantified for a stock extruder under forced and natural convection while printing polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS). Finally, a modified cold-end using a heat pipe to relocate heat rejection to an elevated heat sink was tested under identical conditions, assuming fan failure. Elevated heat-rejection locations experienced lower ambient temperatures and improved natural-convection heat transfer. Relative to the stock configuration, the augmented design reduced cold-end temperatures and improved thermal stability during representative printing cycles without continuous active cooling—the improvement percent is ~8%. The results demonstrate that coupling heat-pipe conduction with environmental thermal gradients can mitigate heat creep and improve extruder reliability with lower energy demand. Full article

In this work, we report the synthesis and evaluation of a bioink based on marine collagen, chitosan, and silica-doped hydroxyapatite (HA–SiO₂) for extrusion-based 3D bioprinting. FTIR spectroscopy confirmed amide (I–III) and phosphate/siloxane signals, TGA showed initial dehydration and degradation stages compatible with the process’s thermal handling, and SEM revealed an interconnected porous microstructure. Rheologically, the ink exhibited elastic dominance (G′ > G″) within the linear range and pseudoplastic, shear-thinning behavior—consistent with pneumatic extrusion. Process evaluation on a BIO X printer (14 G nozzle, low print speeds, moderate pressure, cartridge at 37 °C to 45 °C, and a cooled build platform) enabled deposition of strands with local shape retention. However, filament continuity was limited and line width varied, indicating only preliminary printability and a narrow operating window. Overall, physicochemical, microstructural, and rheological evidence supports the formulation’s viability as a starting point for scaffold fabrication. Full article

The Al–Cu–Mg–Ag alloys have excellent specific strength, good heat resistance and have a wide range of applications in the aerospace and automotive industries. However, industrial production of such alloys is a great challenge owing to the addition of Ag, which limits their widespread application. In this work, the industrial continuous cast and continuous extrusion (Conform) processes were employed to prepare Al–5Cu–0.4Mg–0.1Zr (–0.4Ag) alloys, and the effects of Ag addition on the microstructural characteristics and mechanical properties during processing and heat treatment were investigated. The results indicated that Ag addition significantly refined grain size, increased high-angle grain boundary fraction and grain orientation difference in as-cast Al–5Cu–0.4Mg–0.1Zr (–0.4Ag) alloys, and suppressed excessive grain coarsening during homogenizing annealing. During Conform, Ag further refined grain size, increased subgrain number and enhanced grain orientation difference in extruded alloys. For the aging heat treatment, the T6 process demonstrated superior strengthening effects compared to the T5 process. Following T6 treatment, Ag promoted efficient and uniform precipitation of the Ω (Al₂CuMgAg) phase and then significantly enhanced peak hardness (160 HV) and tensile strength (511.46 ± 2.06 MPa). Additionally, Ag accelerated second-phase dissolution throughout the entire process and produced finer, denser ductile dimples on tensile fracture surfaces to gain good strength–ductility balance. Full article

Piezoresistive pressure sensing has broad application prospects in wearable fields such as human–machine interaction, physiological signal detection, and electronic skin. As a high-performance conductive filler, multi-walled carbon nanotubes (MWCNTs) have demonstrated extensive application potential across various domains. However, polymer composites filled with MWCNTs exhibit complex behavior during the printing process, which increases the difficulty of applying extrusion-based 3D printing technology. To this end, this study systematically investigated the extrusion 3D printing process of MWCNTs/polydimethylsiloxane (PDMS) composites. In this research, MWCNTs/PDMS composites with MWCNTs mass fractions of 1 wt%, 2 wt%, 3 wt%, and 4 wt% were prepared. The printability of the materials at each ratio was systematically explored, and rational printing process parameters were determined. On this basis, the influence of MWCNTs mass fraction on sensor performance was analyzed through tensile testing. Finally, three sets of experiments, including palm gesture recognition and gripping tests, elbow joint motion monitoring, and continuous pressure monitoring, successfully verified the feasibility of the fabricated sensors in human motion monitoring. The results demonstrate that the sensors made of this composite material via extrusion 3D printing possess excellent application potential in the field of flexible wearable electronics. Full article

This study investigates the machinability of Continuous Fiber-Reinforced Thermoplastic Composite (CFRTP) produced via Material Extrusion (MEX) additive manufacturing, focusing on drilling as a critical post-processing step in hybrid manufacturing. CFRTP components, fabricated from 3K carbon fibers and a PLA matrix, were subjected to systematic drilling tests under varying cutting speeds (50–110 m/min) and feed rates (0.06–0.24 mm/rev). Thrust force (Fz) and torque (Mz) were recorded using a high-precision dynamometer to evaluate the influence of cutting parameters on mechanical loads and damage mechanisms. Results indicate that increasing the feed rate significantly increases Fz and Mz, promoting fiber pull-out, delamination, and edge deformation, particularly at hole entry and exit regions. Conversely, higher cutting speeds reduce Fz and Mz due to thermal softening of the PLA matrix, enabling more controlled fiber–matrix interaction. Microscopic analyses revealed that damage severity correlates strongly with mechanical load levels. While high feed rates caused pronounced surface irregularities and matrix smearing, low feed rates combined with high cutting speeds yielded smoother hole morphology and preserved fiber–matrix integrity. The study concludes that optimal drilling conditions for CFRTP materials involve low feed rates and high cutting speeds, minimizing mechanical loads and suppressing damage formation. These findings provide a scientific basis for precision finishing strategies in hybrid manufacturing, enhancing dimensional accuracy and structural reliability of CFRTP components for advanced engineering applications. Full article

Low-moisture meat analogs (LMMAs) typically exhibit highly expanded structures with large air cells, which differ from the dense and fibrous architecture observed in high-moisture systems. This study investigated the role of isolated pea protein (IPP) in extrusion-induced protein gelation and gel-like network formation in LMMAs produced by low-moisture extrusion. By partially substituting isolated soy protein (ISP) with IPP, changes in expansion behavior, protein network structure, and gel-related physicochemical properties were systematically evaluated. Increasing IPP content markedly reduced expansion and air-cell size, leading to the formation of a dense and continuous gel-like protein network with enhanced fibrous alignment. At IPP substitution levels of 20–30%, the extrudates exhibited gel structures and fibrous characteristics comparable to those of high-moisture meat analogs. As IPP incorporation increased, water holding capacity, springiness, and cohesiveness declined, while mechanical resistance parameters, including chewiness, cutting strength, and integrity index, progressively increased, indicating gel network densification. Nitrogen solubility index analysis further revealed distinct protein denaturation and gelation behaviors between IPP- and ISP-based systems. These results demonstrate that controlled incorporation of IPP effectively modulates extrusion-induced gelation and gel network architecture in low-moisture meat analogs, providing mechanistic insights into gel-based structuring strategies for plant-based meat systems. Full article

Healthcare-associated infections (HAIs) remain a major challenge in clinical environments, where textiles frequently act as reservoirs for pathogenic bacteria. This study reports the development, upscaling, and hospital validation of antimicrobial hospital apparel incorporating copper nanoparticles (CuNPs) embedded within polyamide-6 core–sheath bicomponent filaments. A CuNP–polyamide masterbatch was produced through ultrasound-assisted melt extrusion and processed into continuous filament yarns under varying draw conditions. Filaments drawn at 1500 m/min exhibited uniform nanoparticle distribution, improved sheath exposure, and suitable mechanical properties for weaving. The optimized yarns were incorporated into woven narrow fabrics and integrated into prototype medical coats. Antimicrobial assays demonstrated >90% inhibition of S. aureus and 70% inhibition of P. aeruginosa. Durability testing showed minimal activity loss after 10 laundering cycles and no significant decline after up to 200 abrasion cycles. Cytotoxicity evaluation confirmed high fibroblast viability (97%), supporting the biocompatibility of the materials. In a hospital field trial, antimicrobial uniforms achieved substantial reductions in microbial burden, particularly at sleeve cuffs (30% total bacteria, 55% Gram-positive, 70% Gram-negative). It was demonstrated that intrinsically antimicrobial CuNP-embedded textiles offer a durable and safe strategy for reducing bacterial contamination in healthcare apparel and improving infection-control practices. Full article

In this study, the geometric and compressive characteristics of a rhombicuboctahedron architecture fabricated by material extrusion were investigated. The compressive results showed that increasing the number of unit cells led to the specific compressive strength remaining nearly constant. In contrast, as the strut thickness increased, the structures exhibited higher compressive strength, specific compressive strength, and elastic modulus. In particular, the thickest configuration exhibited no premature fracture or abrupt stress drop, instead demonstrating a progressive densification behavior with continuously increasing stress. Furthermore, a pallet prototype was fabricated to demonstrate practical feasibility. The non-cubic, recessed geometry of the rhombicuboctahedron units enabled geometric interlocking between stacked pallets, increasing surface-induced friction and contributing to enhanced stacking stability and anti-slip performance. These results demonstrate the potential of rhombicuboctahedron architectures as lightweight, scalable, and mechanically reliable structural elements for compression-dominated applications enabled by additive manufacturing. Full article

Concrete 3D printing (3DCP) combines materials science with material processing technologies to enable automated, additive construction. This review summarizes findings from the literature and industrial practice on 3DCP mortar formulation with emphasis on the material processing chain. The workflow is examined from raw material storage through handling, mixing, and deposition. The roles of binders, aggregates, dispersed reinforcement, and chemical admixtures are discussed in relation to rheological behavior, buildability, and early-age mechanical performance. The analysis covers storage, dosing, and mixing strategies with respect to mix consistency and overall process reliability, while mortar pumping and extrusion are addressed alongside nozzle-injected additives and automation. Finally, limitations and scalability challenges are outlined with research directions such as continuous mixing, in-line monitoring, and adaptive mix formulation for on-site applications. Full article