Search Results (78)

This paper presents the development and validation of a cost-effective 3D-printed conductive phantom for EEG sensing system validation that achieves 85% cost reduction (£48.10 vs. £300–£500) and 48-hour fabrication time while providing consistent electrical properties suitable for standardized electrode testing. The phantom was fabricated using conductive PLA filament in a two-component design with a conductive upper section and a non-conductive base for structural support. Comprehensive validation employed three complementary approaches: DC resistance measurements (821–1502 $\mathsf{\Omega }$), complex impedance spectroscopy at 100 Hz across anatomical regions (3.01–6.4 k$\mathsf{\Omega }$ with capacitive behavior), and 8-channel EEG system testing (5–11 k$\mathsf{\Omega }$ impedance range). The electrical characterization revealed spatial heterogeneity and consistent electrical properties suitable for comparative electrode evaluation and EEG sensing system validation applications. To establish context, we analyzed six existing phantom technologies including commercial injection-molded phantoms, saline solutions, hydrogels, silicone models, textile-based alternatives, and multi-material implementations. This analysis identifies critical accessibility barriers in current technologies, particularly cost constraints (£5000–20,000 tooling) and extended production timelines that limit widespread adoption. The validated 3D-printed phantom addresses these limitations while providing appropriate electrical properties for standardized EEG electrode testing. The demonstrated compatibility with clinical EEG acquisition systems establishes the phantom’s suitability for electrode performance evaluation and multi-channel system validation as a standardized testing platform, ultimately contributing to democratized access to EEG sensing system validation capabilities for broader research communities. Full article

This work presents a multiscale, microstructure-aware framework for predicting fatigue strength distributions in additively manufactured (AM) alloys—specifically, laser powder bed fusion (L-PBF) AlSi10Mg and Ti-6Al-4V—by integrating density functional theory (DFT), instrumented indentation, and Bayesian inference. The methodology leverages principles common to all 3D printing (additive manufacturing) processes: layer-wise material deposition, process-induced defect formation (such as porosity and residual stress), and microstructural tailoring through parameter control, which collectively differentiate AM from conventional manufacturing. By linking DFT-derived cohesive energies with indentation-based modulus measurements and a MAP-based statistical model, we quantify the effect of additive-manufactured microstructural heterogeneity on fatigue performance. Quantitative validation demonstrates that the predicted fatigue strength distributions agree with experimental high-cycle and very-high-cycle fatigue (HCF/VHCF) data, with posterior modes and 95 % credible intervals of ${\widehat{\sigma }}_f^{\mathrm{AlSi}10\mathrm{Mg}}={86}_{-7}^{+8}\mathrm{MPa}$ and ${\widehat{\sigma }}_f^{\mathrm{Ti}–6\mathrm{Al}–4\mathrm{V}}={115}_{-9}^{+10}\mathrm{MPa}$, respectively. The resulting Woehler (S–N) curves and Paris crack-growth parameters envelop more than 92 % of the measured coupon data, confirming both accuracy and robustness. Furthermore, global sensitivity analysis reveals that volumetric porosity and residual stress account for over 70 % of the fatigue strength variance, highlighting the central role of process–structure relationships unique to AM. The presented framework thus provides a predictive, physically interpretable, and data-efficient pathway for microstructure-informed fatigue design in additively manufactured metals, and is readily extensible to other AM alloys and process variants. Full article

Three-dimensional (3D) printing has emerged as a transformative technology in dental splint fabrication, offering significant advancements in customization, production speed, material efficiency, and patient comfort. This comprehensive review synthesizes the current literature on the clinical use, benefits, limitations, and future directions of 3D-printed dental splints across various disciplines, including prosthodontics, orthodontics, oral surgery, and restorative dentistry. Key 3D printing technologies such as stereolithography (SLA), digital light processing (DLP), and material jetting are discussed, along with the properties of contemporary photopolymer resins used in splint fabrication. Evidence indicates that while 3D-printed splints generally meet ISO standards for flexural strength and wear resistance, their mechanical properties are often 15–30% lower than those of heat-cured PMMA in head-to-head tests (flexural strength range 50–100 MPa vs. PMMA 100–130 MPa), and study-to-study variability is high. Some reports even show significantly reduced hardness and fatigue resistance in certain resins, underscoring material-specific heterogeneity. Clinical applications reviewed include occlusal stabilization for bruxism and temporomandibular disorders, surgical wafers for orthognathic procedures, orthodontic retainers, and endodontic guides. While current limitations include material aging, post-processing complexity, and variability in long-term outcomes, ongoing innovations—such as flexible resins, multi-material printing, and AI-driven design—hold promise for broader adoption. The review concludes with evidence-based clinical recommendations and identifies critical research gaps, particularly regarding long-term durability, pediatric applications, and quality control standards. This review supports the growing role of 3D printing as an efficient and versatile tool for delivering high-quality splint therapy in modern dental practice. Full article

This paper presents an FPGA-based configurable drive waveform generation system for industrial inkjet printheads, targeting the need for real-time adaptability in printing across heterogeneous materials. The system adopts a three-array waveform description method, enabling flexible configuration and precise generation of drive waveforms with adjustable geometry, segment duration, and voltage levels. Through a modular and parameterized design, the system supports rapid waveform switching during column-wise printing without interrupting the printing process, addressing the challenges posed by varying ink absorption characteristics across different substrates. Experimental results demonstrate the system’s capability to achieve smooth waveform transitions within an interval of 830 µs between columns, with data loading times as low as 4 µs. This efficient performance ensures seamless operation and high flexibility. The proposed approach significantly reduces the hardware cost and improves printing efficiency, offering a scalable and robust solution for next-generation industrial inkjet applications involving complex and dynamic material surfaces. Full article

To address the problem of excessive ablation in conventional laser processing caused by the inhomogeneous energy distribution at the focal point, along with the inherent heterogeneity and surface irregularities of textile materials, a new method for laser printing elastic bandage fabrics was developed. We used flat top light sources, short focal field mirrors, and low power lasers instead of the Gaussian light sources, long focal field mirrors, and high-power lasers used in traditional methods. First, the sample was preheated, and the aspherical lens system was designed and simulated. Then, the physical and chemical properties of laser-processed elastic bandage fabrics were investigated. Finally, based on single-factor experiments, orthogonal experimental analysis was conducted to determine the optimal process parameters. The results show that the optimized optical path can effectively improve the uniformity of the temperature field during laser scanning and enhance focusing performance; as energy gradually accumulates, chemical bonds in polymer molecules break; when the elastic bandage fabric is in a highly elastic state, it exhibits appropriate breaking strength and color difference. The best parameters obtained from the single-factor experiment are as follows: laser power range of 25–34 W, scanning speed range of 2200–2800 mm/s, preheating temperature range of 125–200 °C. The best parameters obtained from the orthogonal experiment are as follows: laser power 28 W, scanning speed 2800 mm/s, and the preheating temperature 175 °C. Full article

Recent studies focus on recovering materials from Waste Electrical and Electronic Equipment (WEEE). Printed Circuit Boards (PCBs) are promising due to their heterogeneous composition, which includes precious metals, ceramics, and polymers. This research analyzes the leaching process of computer PCB waste to recover valuable metals such as copper and gold. The study involved physical-mechanical processing of PCB samples followed by chemical composition characterization. Metal extraction was performed through a three-stage leaching process. The first two stages used 2 M and 3 M sulfuric acid with hydrogen peroxide as leaching agents, achieving about 75% copper extraction. In the third stage, parameters for gold leaching using thiosulfate were evaluated, including concentrations of ammonium hydroxide and copper sulfate, reaction times (1–4 h), and temperatures (30, 40, and 50 ${\phantom{­}}^{\circ }$C). The leaching solution comprising 0.12 M sodium thiosulfate, 0.2 M ammonium hydroxide, and 20 mM copper sulfate yielded maximum gold extractions of 14.76% for fine and 15.73% for coarse fractions at 40 ${\phantom{­}}^{\circ }$C. In conclusion, the proposed method for recovering metals from PCBs can reduce the environmental impact of improper WEEE disposal while promoting a circular economy of secondary raw materials. Full article

This study focuses on the fabrication and application of heterogeneous acid catalytic filaments for free fatty acid (FFA) reduction in crude palm oil (CPO) via esterification. Amberlyst-15 catalyst was blended with acrylonitrile butadiene styrene (ABS) using a single-screw filament extruder to produce Amberlyst-15/ABS catalytic filaments. A 5 wt.% concentration of fine Amberlyst-15 particles was considered optimal for blending with ABS, making them a suitable acid catalyst for FFA reduction. The mechanical properties, thermal behavior, and morphology of the Amberlyst-15/ABS catalytic filaments were assessed. The esterification process was optimized by varying three independent variables: the methanol-to-oil molar ratio, catalytic filament loading, and reaction time. The results revealed that under the recommended conditions—26.7:1 methanol-to-oil molar ratio, 78.5 wt.% catalytic filament loading, and a reaction time of 20.2 h at 500 rpm and 60 °C—the FFA content in CPO was reduced from 10.05 to 0.83 wt.%. Additionally, the reusability of the catalytic filaments was evaluated under the recommended conditions of the esterification process. The results demonstrated that the filaments remained effective for at least two cycles, achieving FFA levels below 2 wt.%, thereby confirming their stability and catalytic efficiency. The methodology employed in this study for the preparation and characterization of Amberlyst-15/ABS catalytic filaments offers a promising approach for fabricating acid catalytic materials via 3D printing, especially for heterogeneous catalysis in esterification reactions. Full article

Cancer is the second leading cause of death worldwide, after cardiovascular disease, claiming not only a staggering number of lives but also causing considerable health and economic devastation, particularly in less-developed countries. Therapeutic interventions are impeded by differences in patient-to-patient responses to anti-cancer drugs. A personalized medicine approach is crucial for treating specific patient groups and includes using molecular and genetic screens to find appropriate stratifications of patients who will respond (and those who will not) to treatment regimens. However, information on which risk stratification method can be used to hone in on cancer types and patients who will be likely responders to a specific anti-cancer agent remains elusive for most cancers. Novel developments in 3D bioprinting technology have been widely applied to recreate relevant bioengineered tumor organotypic structures capable of mimicking the human tissue and microenvironment or adequate drug responses in high-throughput screening settings. Parts are autogenously printed in the form of 3D bioengineered tissues using a computer-aided design concept where multiple layers include different cell types and compatible biomaterials to build specific configurations. Patient-derived cancer and stromal cells, together with genetic material, extracellular matrix proteins, and growth factors, are used to create bioprinted cancer models that provide a possible platform for the screening of new personalized therapies in advance. Both natural and synthetic biopolymers have been used to encourage the growth of cells and biological materials in personalized tumor models/implants. These models may facilitate physiologically relevant cell–cell and cell–matrix interactions with 3D heterogeneity resembling real tumors. Full article

The increasing global demand for metals, driven by technological progress and the energy transition, has led to an acceleration in the expansion of the mining and metallurgical industry, resulting in an increase in the generation of mine tailings. This waste, which is of heterogeneous composition and has high contaminant potential, represents significant environmental and social challenges, affecting soils, water, and the geotechnical stability of tailings. The accumulation of these mine tailings poses a problem not only in terms of quantity, but also in terms of physicochemical composition, which exacerbates their environmental impact due to the release of heavy metals, affecting ecosystems and nearby communities. This article reviews the potential of geopolymerization and 3D printing as a technological solution for the management of tailings, offering an effective alternative for their reuse as sustainable building materials. Alkaline activation of aluminosilicates facilitates the formation of N–A–S–H and C–A–S–H cementitious structures, thereby providing enhanced mechanical strength and chemical stability. Conversely, 3D printing optimizes structural design and minimizes material consumption, thereby aligning with the principles of a circular eco-economy and facilitating carbon footprint mitigation. The present study sets out to compare different types of tailings and their influence on geopolymer reactivity, workability, and mechanical performance. In order to achieve this, the study analyses factors such as the Si/Al ratio, rheology, and setting. In addition, the impact of alkaline activators, additives, and nanoparticles on the extrusion and interlaminar cohesion of 3D printed geopolymers is evaluated. These are key aspects of their industrial application. A bibliometric analysis was conducted, which revealed the growth of research in this field, highlighting advances in optimized formulations, encapsulation of hazardous waste, CO₂ capture, and self-healing geopolymers. The analysis also identified technical and regulatory challenges to scalability, emphasizing the necessity to standardize methodologies and assess the life cycle of materials. The findings indicated that 3D printing with tailings-derived geopolymers is a viable alternative for sustainable construction, with applications in pavements, prefabricated elements, and materials resistant to extreme environments. This technology not only reduces mining waste but also promotes the circular economy and decarbonization in the construction industry. Full article

The study investigates the mechanical characterization of PET-G components fabricated via Fused Deposition Modeling (FDM), integrating experimental testing with advanced numerical modeling. Initially, an extensive parametric analysis was conducted to determine the optimal printing conditions, focusing on temperature, speed, and infill density to ensure reliable and repeatable sample fabrication. Subsequently, the study employs an inverse problem-solving approach that combines Digital Image Correlation (DIC) with Finite Element Method Updating (FEMU) to identify the material parameters, specifically Young’s modulus and Poisson’s ratio. The methodology allows for a precise evaluation of mechanical properties by iteratively minimizing discrepancies between experimental strain fields and FEM simulations. The results reveal significant dependencies of material stiffness on infill pattern and density, with Young’s modulus varying up to 20% between different configurations. Additionally, the study highlights the limitations of conventional tensile testing for FDM materials, emphasizing the necessity for advanced full-field measurement techniques to account for anisotropy and microstructural heterogeneity. The proposed methodology enhances the accuracy of material characterization, contributing to the development of more reliable predictive models for 3D-printed components. The research provides valuable insights for optimizing FDM process parameters and establishing standardized testing protocols for additively manufactured materials. Full article

Objective: To conduct a systematic review on the mechanical properties of 3D printed resin-based composites when compared with those of subtractively manufactured resin-based composites. Materials and Methods: In vitro studies comparing the mechanical properties of additively and subtractively manufactured resin-based composites were sought. A systematic search, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), was performed on four databases (PubMed, Embase, Web of Science, and Scopus) for articles published until 23 December 2024. The quality of the studies was assessed with the QUIN tool (risk-of-bias tool for assessing in vitro studies conducted in dentistry) and those assessed with a high risk of bias were excluded. Results: Of the 1058 screened articles, 13 were included in this review. A noticeable heterogeneity emerged in the methodologies employed, mainly regarding samples’ fabrication techniques, materials involved, and parameters analyzed. The most investigated mechanical property was fracture resistance, followed by microhardness, flexural strength, and wear behavior. Among the tested materials, the most used 3D printable resins were VarseoSmile Crown Plus (Bego) and Crowntec (Saremco Dental), whereas for the subtractive groups, the most investigated was Brilliant Crios (Coltène). Conclusions: The mechanical properties of 3D printed resins designed for permanent restorations are still lower than those of their subtractively manufactured counterparts. Moreover, in the long term, the degradation processes that inevitably occur might significantly increase their chances of failure. Full article

Colored 3D printing, as one of the crucial directions in 3D printing technology, has been widely applied in various fields in recent years. Compared to traditional 3D printing, colored 3D printing introduces color information to achieve multi-material identification of different regions in the model structure, enabling the fabrication of heterogeneous and complex components. This presents unique advantages in both visual effects and functionality, making it of significant value in fields such as metal manufacturing, bioengineering, and artistic design. However, during the construction of colored models, technical challenges such as low-slicing contour accuracy and poor color reproduction persist. Existing slicing methods for colored models are often accompanied by contour offset, deformation, color distortion, and low rendering efficiency, severely limiting the application scope of colored 3D printing technology. To address these challenges, this paper proposes a “Fast Slicing Method for Colored Models Based on Colored Triangular Prisms and OpenGL”. This method first constructs colored triangular prisms to effectively solve the problems of color contour offset and deformation, achieving uniform thickness offset of the colors. Then, by utilizing OpenGL rendering technology, the method overcomes color abruptness, simplifies bitmap rendering processes, and ensures smooth color transitions while significantly improving rendering efficiency. In summary, the proposed slicing method can effectively enhance the accuracy of slicing contours and color reproduction, significantly expanding the application range of colored 3D printing. Full article

The objective of this work is to review the literature on the use of three-dimensional scaffolds obtained by printing for the regeneration of bone defects in the maxillofacial area. The research question asked was: what clinical experiences exist on the use of bone biomaterials manufactured by CAD/CAM in the maxillofacial area? Prospective and retrospective studies and randomized clinical trials in humans with reconstruction area in the maxillofacial and intraoral area were included. The articles had to obtain scaffolds for bone reconstruction that were designed by computer processing and printed in different materials. Clinical cases, case series, in vitro studies and those that were not performed in humans were excluded. Six clinical studies were selected that met the established inclusion criteria. The selected studies showed heterogeneity in their objectives, materials used and types of regenerated bone defects. A high survival rate was found for dental implants placed on 3D-printed scaffolds, with rates ranging from 94.3% to 98%. The materials used included polycaprolactone, coral-derived hydroxyapatite, biphasic calcium phosphate (BCP) and bioceramics. The use of CAD/CAM technology is seen as key for satisfying variations in the shapes and requirements of different fabrics and size variations between different individuals. Furthermore, the possibility of using the patient’s own stem cells could revolutionize the way bone defects are currently treated in oral surgery. The results indicate a high survival rate of dental implants placed on 3D-printed scaffolds, suggesting the potential of this technology for bone regeneration in the maxillofacial mass. Full article

Hydrogels as biomaterials possess appropriate physicochemical and mechanical properties that enable the formation of a three-dimensional, stable structure used in tissue engineering and 3D printing. The integrity of the hydrogel composition is due to the presence of covalent or noncovalent cross-linking bonds. Using various cross-linking methods and agents is crucial for adjusting the properties of the hydrogel to specific biomedical applications, e.g., for direct bioprinting. The research subject was mixtures of gel-forming polymers: sodium alginate and gelatin. The polymers were cross-linked ionically with the addition of CaCl₂ solutions of various concentrations (10%, 5%, 2.5%, and 1%) and covalently using squaric acid (SQ) and dialdehyde starch (DAS). Initially, the polymer mixture’s composition and the hydrogel cross-linking procedure were determined. The obtained materials were characterized by mechanical property tests, swelling degree, FTIR, SEM, thermal analysis, and biological research. It was found that the tensile strength of hydrogels cross-linked with 1% and 2.5% CaCl₂ solutions was higher than after using a 10% solution (130 kPa and 80 kPa, respectively), and at the same time, the elongation at break increased (to 75%), and the stiffness decreased (Young Modulus is 169 kPa and 104 kPa, respectively). Moreover, lowering the concentration of the CaCl₂ solution from 10% to 1% reduced the final material’s toxicity. The hydrogels cross-linked with 1% CaCl₂ showed lower degradation temperatures and higher weight losses than those cross-linked with 2.5% CaCl₂ and therefore were less thermally stable. Additional cross-linking using SQ and DAS had only a minor effect on the strength of the hydrogels, but especially the use of 1% DAS increased the material’s elasticity. All tested hydrogels possess a 3D porous structure, with pores of irregular shape and heterogenic size, and their swelling degree initially increased sharply to the value of approx. 1000% during the first 6 h, and finally, it stabilized at a level of 1200–1600% after 24 h. The viscosity of 6% gelatin and 2% alginate solutions with and without cross-linking agents was similar, and they were only slightly shear-thinning. It was concluded that a mixture containing 2% sodium alginate and 6% gelatin presented optimal properties after gel formation and lowering the concentration of the CaCl₂ solution to 1% improved the hydrogel’s biocompatibility and positively influenced the cross-linking efficiency. Moreover, chemical cross-linking by DAS or SQ additionally improved the final hydrogel’s properties and the mixture’s printability. In conclusion, among the tested systems, the cross-linking of 6% gelatin–2% alginate mixtures by 1% DAS addition and 1% CaCl₂ solution is optimal for tissue engineering applications and potentially suitable for 3D printing. Full article

Plastic packaging waste (PPW) can be considered as solid waste with harmful effects on the environment or as a material with recycling potential in terms of sustainable development in a circular economy. Knowing the amount of PPW generated is very important as it is related to the availability of this material for recycling and determines the actual recycling rate (denominator of a fraction). PPW is very heterogeneous and contains a certain number of impurities (e.g., product residues, direct printing, glue, labels, plastic sleeves, cap, etc.). According to EU law, an annual report (for the data in 2021) on the masses of both the PPW actually recycled (PPW_R) (“targeted materials”) and impurities (“non-targeted materials”) must be prepared and submitted to the European Commission. The PPW_R is used for the calculation of the recycling rate (the numerator in a fraction). The impurities should be considered for the calculation of own resources (national contributions to the general EU budget based on the uniform call rate of 0.80/kg of non-recycled PPW). To date, the Council of the EU has not proposed a method for calculating these amounts, so they have only been estimated. The present study (the first of its kind in Poland) aimed to estimate the number of impurities in PPW and the actual amount of PPW_R at the calculation point using a method accepted by the EU. In the installations, PPW (plastic packaging (15 01 02), multi-material packaging (15 01 05) and mixed packaging waste (15 01 06)) is recycled together with other plastic waste (plastic (16 01 19), plastic (17 02 03), plastic and rubber (19 12 04), and plastics (20 01 39)). It was assumed that the proportions of the mass of individual types of PPW in the total mass of plastic waste processed in the installation were proportional to the mass of impurities in these individual types of PPW. It was found that the average percentage of impurities in PPW was 4.40–6.90%, which seems to be relatively low. However, this means that, when calculating the PPW_R, the mass of impurities should be subtracted from the mass of PPW entering the recycling process. As a result, the mass of PPW_R at the calculation point in 2021 in Poland was almost 30,000 tonnes lower than the original mass entering the installation. Thus, applying the uniform call rate to the weight of impurities in the PPW increases Poland’s own resources by approx. 24 million euros. Full article