Osteochondral defects have become a common clinical problem. The cartilage-bone interface is complex, and regenerative biomaterials are limited. This is the first study to integrate Continuous plastic flow synthesis (CPFS) derived Zn-doped hydroxyapatite into an electrospun PVA nanofibrous membrane for osteochondral repair. Combined structural and spectroscopic analysis revealed a preserved apatite lattice after zinc integration, with a strong inorganic-polymeric interfacial interaction. The fabricated membrane exhibited smooth nanofibers with an average diameter of 272 ± 2.21 nm, in which Zn-HA was uniformly dispersed. The nanofibrous membrane exhibited considerably better antibacterial efficacy against Staphylococcus aureus and Pseudomonas aeruginosa than Zn-HA. In vitro results confirmed good viability of osteoblasts. In vivo assessment in an osteochondral defect model revealed nearly complete defect repair after 8 weeks, with well-organized trabecular bone formation and restoration of the bone-cartilage structure without a significant inflammatory response. Collectively, these findings reveal synergistic osteoregenerative and antibacterial activity, suggesting that the nanofibrous membrane may serve as a potential material for osteochondral tissue engineering.

Injection molding (IM) is widely used for high-volume, small, and complex plastic components and is increasingly applied to ceramic and metallic parts. However, the high cost and long processing times of conventional tooling hinder its application in prototyping or small series production. Conventional molding tools with straight-drilled channels cool unevenly, causing shrinkage differences and longer cycle times. This study focused on material extrusion-based composite extrusion modeling three-dimensional (3D) printing of large-scale IM tools using metal IM feedstock. Conformal cooling channels were integrated into the tools to enhance cooling efficiency and temperature uniformity, reducing residual stress and defects. Large-scale IM tools were successfully fabricated via composite extrusion modeling 3D printing for the first time, achieving high green and sintered densities of 97.37 ± 0.24% and 98.08 ± 0.10%, respectively, without any visible cracks or delamination. Dimensional accuracy remained within ~0.7 mm, and surface roughness was comparable to that of conventional IM tools. Nevertheless, post-processing is required to address surface waviness and support removal marks. Simulations also demonstrated that conformal-designed tools cool molded parts below 80 °C in 5 s, compared with 20 s for conventional tools. These findings demonstrate the potential of material extrusion-based 3D printing as a cost-effective alternative for producing IM tools with conformal cooling, enabling faster production cycles and more efficient design for fragile geometries.

Material extrusion additive manufacturing (MEX) of ceramics and metals enables fabrication of complex geometries. However, residual stresses during 3D printing cause torsional distortions during post-processing, compromising dimensional accuracy. This study systematically analyses the occurrence and mechanisms of torsional distortion in additively manufactured ceramic and metallic components. Ceramic and metallic feedstocks were selected due to their pronounced differences in thermophysical properties and sintering behavior, including thermal conductivity, binder content, and shrinkage anisotropy, which can influence residual stress development during MEX. The influence of key process parameters such as layer height, printing speed, and printing direction of the print head on torsional distortion is quantified. Experimental results demonstrate that distortions occur in both material systems but can be effectively controlled through printing process optimization. While increasing the layer height leads to a reduction in distortion, changes in printing speed had no significant effect on the degree of deformation. Alternating the printing direction between layers almost completely eliminated deformations, proving to be the most effective strategy across both material systems. These findings provide valuable insights for improving dimensional accuracy in additive manufacturing of highly filled polymers, and offer practical strategies for enhanced dimensional accuracy of final sintered parts.

Background Bone regeneration is regulated by biochemical, mechanical, and electrical cues. Piezoelectric materials have emerged as promising candidates in bone tissue engineering because they generate localized electrical stimulation in response to mechanical loading, potentially enhancing osteogenic differentiation and bone regeneration without the need for external electrical devices. This systematic review aims to evaluate piezoelectric materials for bone tissue engineering, with particular emphasis on their fabrication techniques, material classes, reported biological effects, and associated limitations, challenges, and future prospects. Methods A systematic literature search was conducted in scientific databases to identify experimental studies investigating piezoelectric materials for bone tissue engineering. Eligible studies reported on material fabrication, scaffold design, and in vitro or in vivo biological outcomes. Data were extracted on piezoelectric material types, fabrication techniques, including additive manufacturing, conventional and field-assisted sintering, electrospinning, film coating, casting, foaming, and phase separation and associated biological effects. The advantages, limitations, and applicability of each fabrication approach for scaffold fabrication were systematically compared. Results & discussion The reviewed literature reflects a wide variety of fabrication methods currently explored for piezoelectric constructs in bone tissue engineering. This methodological heterogeneity suggests ongoing efforts to tailor scaffold architecture, material distribution, and functional properties, and is associated with reported advances in scaffold design and performance. Across the included studies, piezoelectric materials are frequently described as being linked to indicators of osteogenic differentiation and bone regenerative responses. However, these findings vary considerably depending on material type, fabrication strategy, and experimental design. Persistent limitations are evident, particularly regarding the trade-off between scaffold porosity and mechanical stability. In addition, evidence from in vivo studies remains limited, restricting the extent to which the reported findings can be generalized. Conclusion Piezoelectric materials show considerable potential for enhancing bone regeneration in tissue engineering applications. Further material optimization, standardized assessment methods, and robust biological validation are required to support clinical translation.

Early pavement deterioration remains a major challenge in asphalt pavement construction, primarily due to temperature-induced distresses such as rutting and fatigue cracking. Conventional bitumen modification methods have been improving bitumen performance, but often rely on nonrenewable or environmentally harmful additives. This study introduces a novel bio-nano ash (BNA) derived from coffee husk ash (CHA) and wood ash (WA) as a suitable bio-nanomaterial for bitumen modification, compared with mineral nano limestone (LS). The bio-nano ashes were prepared by controlled burning in a closed chamber to minimize CO2 emission and secure ecofriendly synthesis. The 70/100 pen bitumen was modified with nanomaterials at 1.5 %, 3.5 %, and 5.5 % by weight of bitumen. The additives were characterized using X-Ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer, Emmette, and Teller method (BET) analysis. Evaluating and modeling tensile metric performance, rheological properties and Bitumen-Fast-Characterization test (BFCT) using a dynamic shear rheometer (DSR) were evaluated. Results revealed that BNA significantly enhanced the tensile maximum force (Fmax) and rutting resistance of modified bitumen compared with nano LS, due to increased complex shear modulus, elevated Equi-shear modulus temperature (TBTSV) and reduced phase angle (delta BTSV). At 5.5 % WA, the maximum peak force and cumulative area were observed, indicating excellent energy absorption and the best overall mechanical performance of modified bitumen. The values of (R2 = 0.999) from linear regression confirmed a strong, consistent link between mechanical and rheological parameters, evidencing bio-nano ash from bio-waste as a high-performance, eco-friendly bitumen modified supporting sustainable asphalt engineering.

High entropy alloys (HEA) are promising candidates as low-cost and precious metal-free catalysts for alkaline exchange membrane electrolysis. As part of the present study, HEA coatings are applied by atmospheric plasma spray coating on porous transport layers of stainless steel fleece. The coatings are fabricated using (Al,Co,Cr,Fe,Ni) powders in the form of an unalloyed metal powder mixture and in the form of a high entropy alloy powder synthesized by planetary ball milling. The resulting coatings are compared with respect to morphology, element distribution and crystal structure. Phases induced by the heat inside the plasma jet are investigated. The plasma spray coating process shown here achieves highly crystalline phases with characteristic FCC and BCC crystal structures, regardless of the type of powder used. Finally, the HEA-coated porous transport layers are characterized in an electrochemical test cell.

Composite extrusion modeling is an advanced material extrusion additive manufacturing process that requires fine-tuning of printing parameters for printing injection molding feedstocks. In order to achieve comparable high-quality parts at different layer thicknesses, the parameters must be optimized for the respective layer thicknesses. In this work, the printing parameters for AISI 8740 low-alloy steel injection molding material are optimized for four different layer thicknesses. The extrusion multiplier values for each layer thickness are tuned, allowing fine adjustment of the printer's screw rotation speed at every layer thickness, resulting in all final parts' maximum densities (>= 98 %) with high accuracies. Scanning electron microscope images, surface roughness measurements, and printing precision tests proved the good and comparable high-quality of all optimized printed parts. Young's modulus, tensile and yield strengths also raised by -24 %, -16 % and -15 %, respectively, compared to the non-optimized printed sintered part. The achieved tensile strength range of (-888-947) MPa and yield strength range of (-574-586) MPa of all optimized printed sintered parts were also higher than those provided by the feedstock manufacturer. This promising approach significantly reduces printing time and manufacturing costs without compromising the printed final parts' quality and mechanical properties. The adjusting screw rotation speed methodology allows broader applicability across diverse material extrusion processes.

The development of electrically active biomaterials, which create electrical cues on demand to foster cellular stimulation, remains a challenge. Here, we utilized a Field-assisted sintering approach to densify barium titanate and 45S5 bioactive glass to create a piezoelectric and potentially bioactive composite. By using Field-assisted sintering, we aimed to fabricate dense piezoelectric specimens, preserving a low degree of crystallization of the bioactive glass to keep bioactivity as high as possible. Therefore, we have varied the compositions of the materials and processed them at different sintering temperatures. This enabled us to produce dense test specimens in the 94 %-98 % relative density range. The samples were successfully polarized, and piezoelectric charge constants d 33 were determined for the composites. The content of bioactive glass and the sintering temperature influence the charge constant d33. 33 . It is in the range of 0.8-3.4 pC/N for the composites, approximately in the order of magnitude assigned to natural tissues such as bone. X-ray diffraction was used to analyze the composition of the processed samples and to investigate the influence of an additional thermal post-treatment. Altogether, we established a process window for field-assisted sintering, allowing the fabrication of a piezoelectric and potentially bioactive biomaterial for tissue engineering.

Steel bearings have been commonly used to counteract induced loading from thermal and traffic conditions in numerous bridges. However, their effectiveness has been compromised due to aging and maintenance limitations, potentially impacting the overall bridge system performance. Existing monitoring techniques for detecting malfunctioning steel bearings lack automation and precision, making them inadequate for long-term and real-time bridge dynamics assessment. This study proposes a response-based approach to identify bearing malfunction by analyzing the traffic-induced response in the bearing vicinity. To implement this approach, laser displacement sensors and wireless acceleration sensors were employed to monitor both malfunctioning and well-functioning steel bridge bearings. Significant differences in bearing performance were observed through response analysis and comparison. Laser sensor measurements revealed larger vertical deflections in the girder at malfunctioned bearing under traffic loading. Moreover, the investigation of the acceleration response in the bearing locality indicated that bearing malfunction could alter the vibrational characteristics of the vicinity, significantly affecting Cross Power Spectral Density (CPSD) and cross-correlation. To quantitatively evaluate the performance of steel bearings, a Condition Score (CS) was introduced. The CS exhibited a strong correlation with bearing damage, providing valuable insights for maintenance and decision-making processes in bridge asset management. This study offers a comprehensive and automated method for identifying steel bridge bearing malfunction by utilizing advanced monitoring techniques and introducing the CS for assessment. The results obtained from this approach can enhance bridge maintenance strategies and contribute to effective bridge asset management.

A critical-size bone defect in load-bearing areas is a challenging clinical problem in orthopaedic surgery. Titanium alloy (Ti6Al4V) scaffolds have advantages because of their biomechanical stability but lack electrical activity, which hinders their further use. This work is focused on the fabrication of Ti6Al4V-Barium Titanate (BaTiO3) bulk composite scaffolds to combine the biomechanical stability of Ti6Al4V with electrical activity through BaTiO3. For the first time, a hollow cylindrical Ti6Al4V is additively manufactured by electron beam melting and combined with piezoelectric BaTiO3 powder for joint processing in field-assisted sintering. Scanning electron microscope images on the interface of the Ti6Al4V-BaTiO3 composite scaffold showed that after sintering, the Ti6Al4V lattice structure bounded with BaTiO3 matrix without its major deformation. The Ti6Al4V-BaTiO3 scaffold had average piezoelectric constants of (0.63 ± 0.12) pC/N directly after sintering due to partial dipole alignment of the BaTiO3 tetragonal phase, which increased to (4.92 ± 0.75) pC/N after a successful corona poling. Moreover, the nanoindentation values of Ti6Al4V exhibited an average hardness and Young's modulus of (5.9 ± 0.9) GPa and (130 ± 14) GPa, and BaTiO3 showed (4.0 ± 0.6) GPa and (106 ± 10) GPa, respectively. It reveals that the Ti6Al4V is the harder and stiffer part in the Ti6Al4V-BaTiO3 composite scaffold. Such a scaffold has the potential to treat critical-size bone defects in load-bearing areas and guide tissue regeneration by physical stimulation.

Composite Extrusion Modeling (CEM) is a screw-based material extrusion (MEX) additive manufacturing process that can produce plastic, metal and ceramic parts based on standard injection molding feed-stocks. In this work, an aluminum oxide feedstock (Al2O3) originally developed for injection molding is processed via a screw-based MEX process for the first time by depositing the plasticized material in layers on the build platform. In order to identify appropriate process parameters, the feedstock is first characterized to estimate the printable temperature processing window. Initially, the best printable extrusion values were estimated in terms of green part density and dimensional accuracy. Afterwards, different nozzle diameters and layer heights are investigated to further improve the green part density and shape accuracy. An extrusion multiplier of 0.14, nozzle diameter of 0.4 mm and a layer height of 0.1 mm were found to be the optimum process parameters to achieve highly dense green parts with a density of 2.7 91 & PLUSMN; 0.001 g/cm3. The optimized parts were also debound and sintered and the shrinkage was investigated. A shrinkage of 17.43% in the z direction and 14.08% in the x-y direction was observed, and a density of 3.92 & PLUSMN; 0.0025 g/cm3 was achieved for the sintered parts.& COPY; 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The culverts are used to safely convey water under railways, highways, and overpasses. They are utilized in drainage areas or water channels and in areas where the bearing capacity of soil is low. The design and construction of this crucial infrastructure need to be improved to meet contemporary demands of reliability and affordability. Precast reinforced box culverts are popular alternatives as they ensure strength, durability, rigidity, and economy. This research seeks to develop an effective and affordable design improvement procedure for a precast box culvert using modern numerical tools. The Finite Element Method (FEM) based approach is used in studying the effects of haunch geometry and additional steel reinforcement on the load-bearing capacity of box culverts. A conventional box culvert is analyzed to create the numerical models in the Abaqus FEM code and to investigate the load-bearing capacity of culverts with an expanded span. The outcomes of the study reveal the critical places for stress concentration as well as the location of maximum damage. It is found that haunch geometry and additional reinforcement at these critical places significantly affect the load-carrying capacity of a culvert. From the comparison of capacity curves of models with and without haunches and diagonal reinforcement, it is found that a 25% increase in load-carrying capacity is achievable with the recommended changes. The proposed design improvement technique can be employed for the cost-effective and safe design of a concrete box culvert with larger span lengths and high water-flowing capacities. The findings of this study are expected to assist practitioners in strength enhancement tasks of box culverts for increased structural stability and drainage efficiency.

Composite Extrusion Modeling (CEM) is an advanced material extrusion additive manufacturing technique for low-cost rapid production of complex parts. In this work, a conventional Metal Injection Moulding (MIM) feedstock is used for 3D printing of low alloy-steel AISI 8740 via CEM. This steel is widely used in aircraft, aerospace, and MIM industries. However, it has, so far, not been processed using CEM-based 3D printing. The influence of four printing parameters, extrusion multiplier, extrusion temperature, nozzle velocity, and layer thickness on green density and surface roughness was explored following the feedstock's investigation. Full-factorial and face-centered response designs were utilized to study the influence of printing parameters and their optimization to achieve maximum green density and minimum surface roughness. The optimized parameters were found to be an extrusion multiplier of 107.6 %, extrusion temperature of 180 °C, nozzle velocity of 20 mm/s and layer thickness of 0.050 mm through a multiple response optimization process. The dense green part with relative densities of ≥ 98 % was achieved with minimum surface roughness of Ra = (2.3 ± 0.1) μm and Rz = (16.1 ± 1.1) μm. Moreover, a scanning electron microscope was utilized to study the surfaces of green parts. The parts printed with optimized printing parameters showed the best quality with minimized printing voids and smooth extrusion.

Beam–column connections are the most critical components of reinforced concrete (RC) structures. They serve as a load transfer path and take a significant portion of the overall shear. Joints in RC structures constructed with no seismic provisions have an insufficient capacity and ductility under lateral loading and can cause the progressive failure of the entire structure. The joint may fail in the shear prior to the connecting beam and column elements. Therefore, several modeling techniques have been devised in the past to capture the non-linear response of such joints. Modeling techniques used to capture the non-linear response of reinforced-concrete-beam–column joints range from simplified lumped plasticity models to detailed fiber-based finite element (FE) models. The macro-modeling technique for joint modeling is highly efficient in terms of the computational effort, analysis time, and computer memory requirements, and is one of the most widely used modeling techniques. The non-linear shear response of the joint panel and interface bond–slip mechanism are concentrated in zero-length linear and rotational springs while the connecting elements are modeled through elastic elements. The shear response of joint panels has also been captured through rigid panel boundary elements with rotational springs. The computational efficiency of these models is significantly high compared to continuum models, as each joint act as a separate supe-element. This paper aims to provide an up-to-date review of macro-modeling techniques for the analysis and assessment of RC-beam–column connections subjected to lateral loads. A thorough understanding of existing models is necessary for developing new mechanically adequate and computationally efficient joint models for the analysis and assessment of deficient RC connections. This paper will provide a basis for further research on the topic and will assist in the modification and optimization of existing models. As each model is critically evaluated, and their respective capabilities and limitations are explored, it should help researchers to improve and build on modeling techniques both in terms of accuracy and computational efficiency.

CaTiO3 is a promising candidate as a pseudo-piezoelectric scaffold material for bone implantation. In this study, pure and magnesium/iron doped CaTiO3 are synthesized by sol-gel method and spark plasma sintering. Energy dispersive X-ray mapping confirm the homogenous distribution of doping elements in sintered samples. High-energy X-ray diffraction investigations reveal that doping of nanostructured CaTiO3 increased the strain and defects in the structure of CaTiO3 compared to the pure one. This led to a stronger pseudo-piezoelectric effect in the doped samples. The charge produced in magnesium doped CaTiO3 due to the direct piezoelectric effect is (2.9 ± 0.1) pC which was larger than the one produced in pure CaTiO3 (2.1 ± 0.3) pC, whereas the maximum charge was generated by iron doped CaTiO3 with (3.6 ± 0.2) pC. Therefore, the pseudo-piezoelectric behavior can be tuned by doping. This tuning of pseudo-piezoelectric response provides the possibility to systematically study the bone response using different piezoelectric strengths and possibly adjust for bone tissue engineering.

The polycrystalline perovskite calcium titanate has an orthorhombic crystal structure at room temperature, which belongs to a centro-symmetric point group. Due to this fact, it does not show piezoelectric behaviour. However, such behaviour is observed in nanostructured calcium titanate prepared by sol-gel synthesis and field assisted sintering. Whereas, the conventionally sintered sample does not show this behaviour. Presumably, the instability of regular TiO6 octahedra results in the off-centering of titanium positions of the field assisted sintered calcium titanate. This phenomenon leads to the generation of electric dipoles due to the lattice distortions produced by the formation of highly localized defects, i.e. oxygen vacancies, during densification by the field assisted sintering. As a result, pseudo-piezoelectric behaviour is observed, which confirms that the field assisted sintering triggers the piezoelectric effect but not the conventional sintering. The charge (Q) produced in the field assisted sintered sample and the piezoelectric constant (d(33)*) values have been determined to be Q = (2.1 +/- 0.3) pC and d(33+)* similar to(7.13 +/- 0.4) pm/V or d(33-)* similar to (-5.95 +/- 0.3) pm/V, respectively. This particular response of nanostructured calcium titanate is of great interest in biomedicine because it can improve the osseointegration of an implant.

This study presents a detailed characterization of self-organized nano- and microstructures on Ti6Al4V evoked by different scanning strategies and fluences with a 300 fs laser operating at a laser wavelength of 1030 nm. The resulting surface morphology was visualized via field emission scanning electron microscopy (FEG-SEM) images of the surface and cross-sections. X-ray diffraction (XRD)-analysis was performed to analyse changes in crystal structures. The chemical surface composition of the near-surface layer was determined by X-ray photoelectron spectroscopy (XPS). Results show a significant influence of heat accumulation while processing with high laser repetition rates on the formation, crystallinity and chemical composition of self-organized structures depending on the scanning strategy. The ablation with different laser scanning strategies led to varying dynamics of growth-mechanisms of self-organized structures, formation of intermetallic phases (Ti3Al), sub-oxides and oxides (Ti6O, TiO) as well as ions (Ti3+, Ti4+) in surface layer reliant on applied fluence. Furthermore, investigations revealed a heat-affected zone up to several micrometers in non-ablated material.

Calcium titanate has an orthorhombic crystal structure and should not exhibit piezoelectric behavior. However, in the present study such behavior is observed in nanostructured calcium titanate prepared by sol–gel synthesis and field assisted sintering. This behavior is referred to as pseudo-piezoelectricity since it is generated by distorted structure. In-situ high-energy X-ray diffraction studies have been performed to investigate this behavior. Strain and defects in the nanostructured bulk material led to its piezoelectric response with non-180° domains reorientation and domains switching under external electric field. The piezoelectric constant is comparable with the piezoelectric constants of natural bone.