Search Results (1,892)

Hydrogels derived from natural and synthetic polymers have emerged as versatile materials with wide applications in food science, biotechnology, and health-related sectors, providing unique opportunities to encapsulate, protect, and deliver bioactive compounds, as well as to create new textures and functional properties in food systems. This review summarizes the latest advances in the design and application of hydrogels, highlighting the critical relationship between polymer structure, crosslinking strategies, and functional performance. The analysis reveals that while significant progress has been achieved, challenges persist in scaling laboratory-scale hydrogel systems to industrially relevant processes, where stability, reproducibility, and regulatory acceptance remain major bottlenecks. Emerging directions in the field include the development of smart hydrogels that respond to environmental stimuli (pH, temperature, or enzymatic activity), sustainable fabrication routes using renewable biopolymers, integration with advanced processing technologies such as 3D printing or microfluidics, and biorefinery approaches emphasizing their role in valorizing agro-industrial by-products into high-value functional materials. Hydrogels represent a promising platform at the interface of polymer science, food technology, and biotechnology, whose continued development will depend on multidisciplinary innovation aiming to meet consumer demands for sustainable, safe, and health-promoting food systems. Full article

Soft biological tissues display highly nonlinear and anisotropic mechanical behavior, which is critical to their physiological function. Replicating these mechanical properties using engineered materials and additive manufacturing represents a significant challenge in biomedical engineering, particularly for surgical simulation, device development, and preclinical testing. The left atrial appendage (LAA) was selected since it plays a central role in thrombus formation during atrial fibrillation, significantly contributing to cardioembolic stroke. This study proposes a framework for reproducing the nonlinear stress–strain behavior of soft tissue using 3D-printed models. The methodology integrates experimental material selection with optimization of key printing parameters to ensure structural reliability and functional mechanical performance. Two polymers—polyurethane (TPU) and a thermoplastic with elastomer-type behavior (TPE)—were selected for their tunable hardness and elasticity. A parametric study was conducted to investigate the effects of Shore A hardness (60A to 100A), infill density (0% to 100%), and external shell number (zero to two) on the tensile performance of printed models. Mechanical testing was performed to extract stress–strain curves and evaluate the mechanical response. The practical implications of this study are significant, demonstrating the potential of additive manufacturing for anatomical reproduction and replicating functional mechanical properties in soft tissue models. Full article

Additive manufacturing of polymer materials, also known as 3D printing, is becoming a key technology for the production of functional parts with the ability to customize the structure and properties according to the application requirements. Polylactide (PLA) is one of the most commonly used materials in this field due to its biodegradability, ease of processing, and adequate strength for lightweight functional components. An important factor that affects the resulting properties of parts is not only the filler structure and density but also the angle at which the material is deposited during the printing process. This article focuses on investigating the influence of the printing angle (0°, 30°, 60° and 90°) and the bulk density of the filler (20%, 40%, 60% and 80%) on the mechanical properties of PLA samples. Two series of samples were prepared—the first was subjected to direct mechanical tests, and the second series was first exposed to freezing conditions and then tested to evaluate the effect of freezing on the material behavior. The samples were tested for tensile strength according to ASTM D638 and for bending strength according to ASTM D790. The results showed that the highest values were achieved in tensile strength in the 60°/80% configuration with a strength of 39.27 MPa, which represents more than a twofold improvement over the weakest configuration (0°/20%–19.58 MPa). In the bending test, the best results were achieved by the 90°/80% sample with a strength of 58.89 MPa, approximately 18% higher than 0°/20%. Cryogenic treatment caused a deterioration of all monitored parameters, especially at low infill densities and at an angle of 0°, where the decrease in strength reached up to 10–13%. These results confirm that the combination of a higher printing angle and a higher infill density is key to optimizing the mechanical properties of PLA parts, while cryogenic treatment has a negative impact on their behavior. Full article

Dynamic covalent bonds within polymer materials have been the subject of ongoing research. These bonds impart polymers, particularly thermosets, with capabilities for self-healing and reprocessing. Concurrently, three-dimensional (3D) printing techniques have undergone rapid advancement and widespread adoption. Since polymers are among the primary materials used in 3D printing, networks featuring dynamic covalent bonds have emerged as a prominent research area. This review outlines approaches for incorporating dynamic covalent bonds into polymers suitable for 3D printing and examines representative studies that leverage these chemistries in material design. Polymers produced using these strategies demonstrate both self-healing and reprocessability, primarily via bond-exchange (metathesis) reactions. In addition, we discuss how the type and amount of dynamic bonds in the network affect the resulting material properties, with particular emphasis on their mechanical, physical, and thermal performance. In particular, the introduction of dynamic covalent bonds seems to significantly improve the degree of anisotropy, which has been the limitation of 3D printing techniques. Finally, we compile recent applications for objects printed from polymers that include dynamic covalent bonds. Full article

Reconstruction of large and complex hard tissue defects remains a major clinical challenge, as conventional autografts and allografts are often limited in availability, biological compatibility, and long-term efficacy, particularly for extensive defects or poor bone quality. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a potent osteoinductive factor capable of initiating the complete cascade of bone formation. However, its clinical use is restricted by dose-dependent complications such as inflammation, ectopic ossification, and osteolysis. This review synthesizes current evidence on the safety profile of rhBMP-2 and examines strategies to enhance its therapeutic index. Preclinical and clinical data indicate that conventional collagen-based carriers frequently cause rapid burst release and uncontrolled diffusion, aggravating adverse outcomes. It is noteworthy that low doses of rhBMP-2 (0.5–0.7 mg/level in anterior cervical discectomy and fusion (ACDF) or 0.5–1.0 mg/level in transforaminal lumbar interbody fusion (TLIF)) provide the optimal balance of efficacy and safety. Advanced biomaterial-based platforms, such as bioceramic–polymer composites, injectable hydrogels, and 3D-printed scaffolds, enable spatially and temporally controlled release while maintaining osteogenic efficacy. Molecular delivery approaches, including chemically modified messenger RNA (cmRNA) and regional gene therapy, provide transient, site-specific rhBMP-2 expression with reduced dosing and minimal systemic exposure. By integrating mechanistic insights with translational advances, this review outlines a framework for optimizing rhBMP-2-based regenerative protocols, emphasizing their potential role in multidisciplinary strategies for reconstructing complex hard tissue defects. Full article

This article demonstrates that 3D-printed parts can replace metal parts in optomechanics in the correct circumstances. Three examples are shown: a clamping fork for pedestal holders where stability is important, an adjustable mirror holder where the rigidity is the main criterion, and a stray light shield where the transmissivity is critical. By combining carbon-fiber-reinforced polymers (CFRPs) with 3D printing, it is possible to produce components that fill the gap between standard 3D-printed plastics and metal parts in terms of strength and stability. These parts are designed to be lighter, more compact, and easier to modify, while keeping good mechanical properties such as resistance to vibration, shape accuracy, and controlled thermal expansion. The article focuses on the application of composite 3D printing on optomechanical components. It compares different methods of composite 3D printing, including fused filament fabrication (FFF) with either chopped fibers or with continuous fiber reinforcement. Three examples from the HiLASE Centre demonstrate how these parts are used in practice, confirming that it is indeed possible to 3D print components that are lighter and cheaper yet still highly functional compared to their off-the-shelf counterparts—for example, lightweight and stiff mounts, shielding against stray laser light, or flexible elements allowing fine mechanical adjustments. Simulations of the deformations are included to compare the printed and metal versions. The article ends with a summary of the benefits and limitations of using 3D-printed composites in optomechanics. Full article

In this study, six common fused filament fabrication (FFF) polymers—PEEK, PLA, PETG, ABS, Nylon, and TPU—were acclimatized at 15%, 45%, and 95% relative humidity (RH) to characterize tensile behavior, including Young’s modulus, maximum strain, and ultimate tensile strength. Separately, mechanical metamaterial samples at relative densities (RD) of 25%, 35%, and 45% were tested in compression at the same RH levels to evaluate stiffness, strength, and Poisson’s ratio. The water absorption process can generally be divided into different stages—rapid uptake (0–12 h), a plateau (12–60 h), and a late rebound (60–100 h)—with a total uptake ranking of Nylon > PETG > PLA ≈ ABS > TPU ≈ PEEK. Samples under tensile and compressive tests show a great difference between properties at different RD and RH levels. Poisson’s ratio indicates that material responses remain predictable at low-to-moderate RH, whereas high RH serves as a critical threshold inducing abrupt Poisson’s ratio behavioral shifts. This study provides systematic validation for the application of 3D-printed metamaterials under varying humidity conditions, such as biomedical implants in human body. Full article

This work investigates the effect of a bio-based plasticizer derived from used sunflower oil on the crystallization behavior of poly (lactic acid) (PLA), comparing it with that of the conventional plasticizer tributyrin. This study aims to explore biodegradable alternatives to petroleum-based materials and to evaluate their potential in modulating PLA crystallization kinetics without altering the crystalline structure of the resulting sustainable material solutions with tailored performance. PLA-based films containing 5%, 10%, and 15% plasticizer were prepared and characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-Ray diffraction (XRD). DSC analysis showed a decrease in the glass transition temperatures upon plasticization, with tributyrin producing a more pronounced effect than the recycled sunflower oil plasticizer. XRD patterns confirmed that the crystalline form of PLA remained unchanged regardless of plasticizer type or content. POM revealed that both plasticizers influenced crystallization kinetics, with the bio-plasticizer promoting larger and more sparsely distributed spherulites than tributyrin, indicating differences in nucleation efficiency and crystal growth. Crystallization kinetics were further analyzed using the Avrami model, the Lauritzen-Hoffman theory, and the isoconversional method. Avrami analysis indicated that nucleation mechanisms were largely unaffected, although the overall crystallization rate increased upon plasticization. Lauritzen-Hoffman analysis confirmed crystallization in Regime III, controlled by nucleation, while isoconversional analysis showed reduced activation energy in plasticized PLA. These findings highlight the ability of bio-derived plasticizers to modulate PLA crystallization, promoting the valorization of a food industry residue as a sustainable plasticizer. This study hopes to contribute relevant knowledge to emerging areas of polymer processing, such as 3D printing, to develop sustainable and high-performance PLA-based materials. Full article

The field of 4D printing has seen rapid advancement in recent years, making it a highly dynamic research domain. This new technology is promising for the development of brand-new lightweight, smart and reliable devices. This article is a literature review of the latest research in 4D printing, focusing on electroconductive thermosensitive Shape Memory Polymers. They are promising thanks to their high strength-to-weight ratio and their large deformability. However, devices made of such materials are difficult to embed into larger systems because of the triggering mechanism needed to actuate them. Electroconductive Shape Memory Polymers can be stimulated by the Joule effect, but the intricacies and interdependence of their properties make them a great scientific challenge. The first part of this article provides a clear explanation of the main concepts of 4D printing. Afterwards, it focuses on Fused Filament Fabrication due to its high customisability and ease of use. A description of the properties of thermosensitive 4D printed specimens is provided in the third part. Finally, their main challenges and intricacies are discussed. Full article

This paper presents an adapted methodology for the prediction of fracture loads in additively manufactured (fused filament fabrication) polymers that exhibit non-linear behavior. The approach is based on the Average Strain Energy Density (ASED) criterion, which is typically limited to materials which develop fully linear-elastic behavior. Thus, in those cases where the material has a certain (non-negligible) amount of non-linear behavior, the ASED criterion needs to be corrected. To extend its applicability, this work proposes a thorough calibration of the ASED characteristic parameters: the critical value of the strain energy and the volume of the corresponding control volume. This enables the extrapolation of the linear-elastic formulation to non-linear situations. The approach is validated using acrylonitrile-styrene-acrylate (ASA) and 10 wt.% carbon-fiber reinforced ASA specimens. Single-edge-notched bending (SENB) specimens with three different raster orientations (0/90, 45/−45, and 30/−60) and four U-notch radii (0.0 mm—crack-like, 0.50 mm, 1.0 mm, and 2.0 mm) were printed and tested. The results demonstrate that the proposed calibration of the ASED criterion allows for accurate predictions of failure loads, providing a reliable tool for the structural integrity assessment of 3D-printed components. Full article

This study offers an integrated synthesis of polymeric materials in biomedical engineering, revealing four major and interlinked research domains: tissue engineering and regenerative medicine, drug delivery and nanomedicine, wound healing and antimicrobial applications, and advanced fabrication through 3D/4D printing and bioprinting. Across these areas, hydrogels, biodegradable composites, and stimuli-responsive polymers emerge as the most influential material classes. The analysis highlights substantial progress in extracellular matrix–mimetic scaffolds, smart drug delivery systems with controlled release, multifunctional wound dressings integrating antimicrobial and healing functions, and patient-specific constructs produced via additive manufacturing. Despite these advances, recurring challenges persist in long-term biocompatibility and safety, scalable and reproducible fabrication, and regulatory standardisation. The results point toward a convergence of bioactivity, manufacturability, and clinical translation, with hybrid natural–synthetic systems and personalised polymeric designs defining the next phase of biomedical polymer innovation. Full article

This article presents the results of research on dust emissions generated by the additive manufacturing process (3D printing) using an FFF method and its impact on the human work environment. The study utilized filaments from three manufacturers in three color variants: neutral, yellow, and black, all made from polylactic acid (PLA), one of the most commonly used polymers in FFF processes. The findings indicated that dust emission levels vary significantly depending on the selection of printing process parameters and the type of filament used. Among the process parameters, the extruder temperature and nozzle diameter have the greatest influence on emission levels. It was shown that at high temperatures and with a small nozzle diameter, the emission level can exceed values hazardous to human health within a short printing time. The maximum recorded Dust Emission Intensity Index (DEII) reached 1058 µg/h when printing with black PLA filament under high-temperature conditions (225 °C, 0.4 mm nozzle). Under these parameters, the predicted dust concentration in a 29 m³ room without ventilation exceeded the WHO limit of 50 µg/m³ for PM₁₀ after approximately 98 min of continuous operation. These results indicate that even desktop-scale FFF printing can pose a measurable risk to indoor air quality when unfavorable process settings are applied. Full article

Composite engine fan blades are critical aircraft engine components, and their failure can compromise the safe and reliable operation of the entire aircraft. To enhance aircraft availability and safety within a condition-based maintenance framework, effective methods are needed to identify damage and monitor the blades’ condition throughout manufacturing and operation. This paper presents a unique experimental framework for real-time monitoring of composite engine blades utilizing state-of-the-art structural health monitoring (SHM) technologies, discussing the associated benefits and challenges. A case study is conducted on a representative Foreign Object Damage (FOD) panel, a substructure of a LEAP (Leading Edge Aviation Propulsion) engine fan blade, which is a curved, 3D-woven Carbon Fiber Reinforced Polymer (CFRP) panel with a secondary bonded steel leading edge. The loading scheme involves incrementally increasing, cyclic 4-point bending (loading–unloading) to induce controlled damage growth, simulating in-operation conditions and allowing evaluation of flexural properties before and after degradation. External damage, simulating foreign object impact common during flight, is introduced using a drop tower apparatus either before or during testing. The panel’s condition is monitored in-situ and in real time by two types of SHM sensors: screen-printed piezoelectric sensors for guided ultrasonic wave propagation studies and surface-bonded Fiber Bragg Grating (FBG) strain sensors. Experiments are conducted until panel collapse, and degradation is quantified by the reduction in initial stiffness, derived from the experimental load-displacement curves. This paper aims to demonstrate this unique experimental setup and the resulting SHM data, highlighting both the potential and challenges of this SHM framework for monitoring complex composite structures, while an attempt is made at correlating SHM data with structural degradation. Full article

Bio-based photo-crosslinkable hydrogels are used in tissue engineering as three-dimensional printable scaffolds due to their functional and biological similarities with the extracellular matrix (ECM). In this work, emerging bioink candidates such as chitosan, alginate and gelatin-based photo-crosslinkable hydrogel were developed using extrusion-based 3D printing to establish a better understanding of their applicability. The polymers were methacrylated by the same methacrylation reaction pathway, which enabled successful light-induced 3D printing. Morphology, swelling (6–40%), mechanical (Young’s modulus, 0.1–0.5 KPa) and rheological properties (300–1000 Pa), degradation kinetics (10->60 days) and printability of the gels were also characterized in identical conditions for the first time. 3D-printability results indicated that methacrylated gelatin enhanced printability, shape fidelity and integrity of printed structures compared to methacrylated alginate, which presents structural instability and poorer printing control due to its low crosslink density. Moreover, cell attachment and Live/Dead assays using bone marrow-derived mesenchymal stem cells (BM-MSCs) showed that all formulations have good biocompatibility for use as scaffolds. Specifically, gelatin-based hydrogels showed a higher level of BM-MSCs attachment and spreading than the other types of hydrogels. Overall, our results suggest that the hydrogels based on these three biopolymers present good potential as a biomaterial for light-induced extrusion-based 3D printing. Full article