Search Results (36)

Additive manufacturing is increasingly integrated into digital prosthodontic workflows for the fabrication of dental models; however, printing-related parameters may influence the dimensional accuracy of clinically relevant regions. This in vitro study evaluated the effect of support spacing on the region-specific dimensional accuracy of masked stereolithography (MSLA)-printed dental models. A standardized typodont model representing a three-unit posterior fixed dental prosthesis preparation in the FDI 24–26 region was digitized to obtain a reference STL dataset. Three support spacing configurations were evaluated: 3 mm, 5 mm, and 7 mm (n = 8 per group). All specimens were fabricated using an MSLA printer and a photopolymer model resin at a layer thickness of 50 μm. After post-processing, the printed models were rescanned and compared with the reference dataset using three-dimensional deviation analysis. Root mean square (RMS) deviations were calculated for global, marginal, intaglio, and adjacent regions. Significant differences were observed in the global (p < 0.001), marginal (p = 0.001), and intaglio (p = 0.010) regions, whereas adjacent regions were not significantly affected (p = 0.070). Increasing support spacing was associated with greater dimensional deviations in the global and intaglio regions. Overall, the 3-mm support spacing demonstrated the most consistent dimensional performance across the evaluated regions. These findings indicate that support spacing is an important design parameter influencing the dimensional predictability of MSLA-printed dental models and highlight the value of region-specific accuracy assessment for optimizing support design in digital prosthodontic workflows. Full article

Lattice structures are widely utilized in lightweight engineering due to their design flexibility and tailorable mechanical properties. However, polymer lattices often exhibit limited load-bearing capacity and moderate crashworthiness under compression. This study proposes a hybrid reinforcement strategy based on the integration of carbon fiber-reinforced polymer (CFRP) rods into polymeric Kelvin-cell lattices. The specimens were manufactured via masked stereolithography, and the effects of rod placement pattern, the number of rods, and rod-length configuration were systematically investigated under quasi-static compression. Crashworthiness was evaluated in terms of force–displacement response, deformation mode, and crashworthiness metrics. Compared with the empty Kelvin-cell lattice, the best-performing hybrid configuration increased energy absorption, specific energy absorption, and mean crushing force by approximately 356%, 307%, and 356%, respectively. Mechanistically, distributed rod placement promoted more uniform load sharing, while the effect of increasing rod number depended strongly on the rod-length configuration. In addition, delayed or sequential reinforcement strategies provided superior performance and an enhanced balance between energy absorption and force efficiency. Regression models and ANOVA consistently identified rod-length configuration as the dominant design variable. These findings demonstrate that CFRP rod reinforcement can effectively enhance the crashworthiness of polymeric Kelvin-cell lattices, provided that the rod placement pattern, rod number, and rod-length configuration are designed jointly. Full article

Electrically conductive photopolymers enable the fabrication of functional 3D-printed components with customized electrical properties, expanding additive manufacturing applications beyond traditional structural uses. This study reports the formulation and characterization of electrically conductive, water-washable photopolymer resins for masked stereolithography (MSLA) through the incorporation of nano-graphite, PEDOT:PSS, and dimethyl sulfoxide (DMSO) as a secondary dopant. Single filler and hybrid resin systems were prepared and processed via MSLA printing, then subjected to sequential thermal treatments, 25 °C curing for 48 h followed by annealing at 80 °C and 120 °C, to investigate conductivity enhancement and microstructural evolution. Electrical characterization via current–voltage (I–V) measurements, referenced to the transversal conductivity (${\sigma }_{TRA}$), showed that the hybrid formulation containing PEDOT:PSS, graphite, and DMSO achieved the highest conductivity (9.40 × 10⁻² S·cm⁻¹), outperforming PEDOT:PSS/graphite systems (2.6 × 10⁻³ S·cm⁻¹) and graphite-only samples (9.76 × 10⁻⁴ S·cm⁻¹). Conductivity increased consistently after each thermal step, indicating enhanced charge transport. Scanning electron microscopy further revealed improved filler dispersion and interconnectivity within the polymer matrix. The synergistic combination of PEDOT:PSS, graphite nanofillers, and DMSO enables MSLA printed components with tunable and reproducible electrical performance. This work demonstrates a scalable strategy for producing functional, water-washable photopolymer resins suitable for applications in sensors, soft electronics, and lightweight conductive structures. Full article

Microfluidics enables spatially controlled nanostructure synthesis by coupling confined flows with surface reactions. In this work, we study how geometry-induced laminar microenvironments govern the in situ formation of Au and Ag nanostructures inside 3D-printed microfluidic reactors. Proof-of-concept fish-scale valves were fabricated by masked stereolithography in three architectures designed to define three recurring zones in the microreactor, inside the fish-scales (zone 1), between the fish-scales (zone 2), and along the rows of fish-scales (zone 3). A Cu thin film was deposited on the inner walls of the channel to serve as the sacrificial surface for galvanic replacement using AgNO₃ or HAuCl₄. Distinct 0D, 1D, and 2D nanostructures were simultaneously obtained in a zone-dependent manner across the valves, including nanoparticle and nanopore-rich regions, nanowires, nanoflakes and clustered 2D features. COMSOL simulations were used to solve the Navier–Stokes equation and extract specific-zone flow descriptors, including Reynolds number, velocity, and wall shear stress, and relate them to the nanostructure morphologies observed by SEM. The flow throughout the devices is strongly laminar, with local Reynolds numbers up to 0.04, exhibiting systematic spatial gradients imposed by the valve geometry. These results provide a design-guided route to tune nanostructure morphology through microchannel architecture under constant global operating conditions. Full article

Construction technologies and materials engineering are collaborating to develop new solutions that enhance energy efficiency. One such solution is thermal barriers filled with phase change material. Thanks to their thermal properties, these innovative barriers are being used in an increasing number of construction projects. Additive manufacturing enables the production of architected thermal barriers with controlled cellular topologies and customized heat transfer pathways. This study investigates the thermal performance of lightweight partitions produced using masked stereolithography (m-SLA) 3D printing, focusing on two geometries: open-cell Kelvin structures and closed-cell honeycomb structures. Two strategies for incorporating phase change material were evaluated: direct addition of 10% and 30% paraffin oil by weight to the photopolymer resin and post-print filling of cellular voids with a PCM-based gel. The aim was to establish the effect of topology and PCM distribution on steady-state thermal parameters and transient temperature stabilization. Experimental testing under cyclic heating–cooling conditions revealed that increasing paraffin oil content significantly improves thermal performance. The open-cell Kelvin structure with 30% PCM exhibited the lowest thermal conductivity (λ = 0.0289 W/(m·K)) and the highest thermal resistance (R = 0.697 m²·K/W). Honeycomb structures achieved λ = 0.0360 W/(m·K) and R = 0.590 m²·K/W at the same PCM content. Transient analysis demonstrated enhanced temperature stabilization, with maximum ΔT values of 29.55 K (30% PCM) and 28.61 K (honeycomb 30%). These results confirm that the geometry produced by additive manufacturing plays a decisive role in governing heat transfer and latent heat utilization in PCM-based thermal barriers. Full article

Vat polymerization-based 3D printing has emerged as a promising approach for the rapid, low-cost, and scalable fabrication of microfluidic devices; however, achieving high-resolution and fully clog-free microchannels using commercial resins remains challenging. In this study, we systematically investigate key printing parameters—including channel orientation, length, layer thickness, and exposure time—to elucidate their effects on channel openness, dimensional fidelity, and surface morphology using a commercially available low-cost masked stereolithography (MSLA) printer and printing resin, thereby establishing quantitative fabrication boundaries that define the transition from fully open to blocked microchannels in practice. Under optimized printing conditions, microchannels with characteristic dimensions exceeding 200 µm were fabricated in a reliable and clog-free manner using standard commercial resins. In addition, by implementing a size-compensated design strategy, we achieved the fabrication of complex droplet generator arrays with a minimum central channel width of 400 µm, while maintaining an internal dimensional deviation below 2.5%. These investigations significantly expand the practical applicability of low-cost MSLA 3D printing for microfluidic device fabrication, providing a scalable and accessible pathway for producing high-fidelity microchannels without reliance on custom resins or post-processing-intensive workflows. Full article

This study addresses the critical need for advanced biomedical materials that possess both potent antimicrobial properties and high biocompatibility to prevent device-related infections and promote healing. To this end, we demonstrate the successful development and comprehensive characterization of functional composite materials based on a photopolymerizable acrylate resin modified with laser-ablated copper nanoparticles (Cu NPs). The synthesized Cu NPs exhibited a monomodal size distribution with a peak at 47 nm, a high zeta potential of −33 mV, and a spherical morphology. Incorporation of Cu NPs into the polymer matrix via Masked Stereolithography (MSLA) enabled the fabrication of complex structures that maintained high surface quality and optical transparency after polishing. Modification of photopolymer resin with Cu NPs significantly increased the strength of the resulting products and caused dose-dependent formation of reactive oxygen species (ROS). The resulting composite materials exhibited strong antibacterial activity against E. coli. Crucially, despite their potent antimicrobial efficacy, the materials showed no cytotoxicity towards human fibroblast cultures. These results highlight the potential of these composites for a new generation of biomedical applications, such as implantable devices and wound coatings, which combine programmable antimicrobial activity with high biocompatibility. Full article

Triply Periodic Minimal Surface (TPMS) structures, with their zero average curvature, excellent energy absorption properties, high specific strength and high surface-to-volume ratio, could be used in a wide range of applications, such as the creation of lightweight and durable structures, grafts and implants. In this study, an internal TPMS structure inspiring trabecular bone and an external TPMS structure inspiring cortical bone were combined with infill density and topologically functionally graded to obtain hybrid structures. The aim of the study was to investigate the effects of functional grading on mechanical properties, energy absorption capacity and surface/volume (S/V) ratio and to determine the best combination. The novelty of the study is to obtain hybrid structures close to bone structures with a functional grading approach. The experimental design of the study was performed using the Design of Experiment (DoE) approach and the Taguchi method. Specimens were created according to the established experimental design and fabricated using a Masked Stereolithography (mSLA)-type 3D printer with bio-resin. The fabricated structures were subjected to compression tests; the results were examined in terms of deformation behavior, first peak, maximum force, energy absorption, specific energy absorption and S/V ratio. The optimal structures for defined input parameters were determined using signal-to-noise (S/N) ratios and ANOVA results. Deformations for diamond and primitive specimens began as shear band formation. Deformations for Neovius structures were mostly as brittle fracture. The highest first peak of 18.96 kN was obtained with the DN specimens, while the highest maximum force of 23.77 kN was obtained with the ND specimens. The best energy absorption property was also obtained with ND. The highest S/V ratio was 5.65 in the GP specimens. The statistical analyses were in accordance with the experimental results. Infill density increases decreased the S/V ratio while increasing all other parameters. This demonstrated the importance of mechanical-strength/porosity optimization for bone scaffold surrogate applications in this study. Full article

The research methodology involved creating a 3D sample model that featured both flat and cylindrical surfaces inclined at angles ranging from 0° to 90° relative to the XY plane. The study investigated the surface topography of additively manufactured samples produced using various technologies, including Fused Filament Fabrication (FFF), masked Stereolithography (mSLA), PolyJet (PJ), and Selective Laser Sintering (SLS). The focus was on how material type, print angle, and measurement location influenced the results. The materials used in the study included PLA, PETG, acrylic resins, PA2200, and VeroClear. Due to the optical properties of the materials used, measurements were carried out on replicas that were prepared using a RepliSet F5 silicone compound from Struers. Consequently, a methodology was developed for measuring surface roughness using the Alicona microscope based on these replicas. A 10× objective lens was used during the measurements, and the pixel size was 0.88 µm × 0.88 µm. Each time, an area of approximately 1 mm × 4 mm was measured. The lowest roughness values were observed for mSLA samples (Sa = 6.72–8.54 µm, Spk + Sk + Svk = 33.36–42.16 µm), whereas SLS exhibited the highest roughness (Sa = 27.86 µm, Spk + Sk + Svk = 183.79 µm). PJ samples exhibited intermediate roughness with significant anisotropy (Sa = 11.65 µm, Spk + Sk + Svk = 72.1 µm), which was strongly influenced by the print angle. FFF surfaces showed directional patterns and layer-dependent roughness, with the Sa parameter being the same (12.44 µm) for both PETG and PLA materials. The steepest slopes were observed for SLS surfaces (Sdq = 7.67), while mSLA exhibited the flattest microstructure (Sdq = 0.48–0.89). Statistical analysis confirmed that material type significantly influenced topography in mSLA, while print angle strongly affected PJ and FFF (although for FFF, further studies would be beneficial). The results of the research conducted can be used to develop a methodology for optimizing the printing process to achieve the required geometric surface structure. Full article

This study aims to evaluate the effects of printing temperature and post-curing duration on double-bond conversion (DBC), mechanical properties, and fabrication reproducibility of three dental photopolymer resins used for fixed dental prostheses (FDPs), denture bases, and direct clear aligners. Specimens were fabricated using stereolithography and masked stereolithography three-dimensional (3D) printers at room temperature (RT, 28 °C) and 50 °C, then subjected to six post-curing durations: 0, 60, 120, 180, 240, and 600 s. DBC was measured using Fourier transform infrared spectroscopy, and tensile strength was measured using tensile testing. Furthermore, fabrication reproducibility for clinical applicability was analyzed using root mean square deviations from 3D scanning. Printing at 50 °C significantly improved the DBC, tensile strength, and fabrication reproducibility of FDP and denture base resins compared to printing at RT, enabling shorter post-curing times (p < 0.001). Clearer aligner resin specimens printed at 50 °C and post-cured for 120 s exhibited the highest fabrication reproducibility (p < 0.001), while tensile strength did not differ significantly from that of RT specimens post-cured for 240 s (p > 0.05). These findings suggest that optimizing printing temperature and post-curing time enhances the mechanical properties and fabrication reproducibility of 3D-printed dental materials. Full article

Stereolithography (SLA) is a 3D printing process in which liquid resin is cured selectively using ultraviolet light; it is dominantly used for rapid tooling and prototyping. This work aims to identify, investigate, and maximize the influence of process parameters such as layer thickness, build orientation, and exposure time on the mechanical performance of biomedical materials through the Taguchi method using masked stereolithography (MSLA). It was found that layer thickness has an inverse relationship with component strength, and the mechanical characteristics are most affected by the vertical build orientation. The improved parameter resulted in an increase of 9.26 percent in tensile, 5.93 percent in flexural, and 17.89 percent in impact strength compared to the average experimental strength. Additionally, an empirical regression model linking strength and process variables was developed. Full article

Vat photopolymerization 3D printing, including stereolithography (SLA), digital light processing (DLP), and masked SLA (mSLA), has transformed dental device fabrication by enabling precise and customizable components. However, the rheological behavior of photopolymer resins is a critical factor that governs the printability, accuracy, and performance of printed parts. This review surveys the role of viscosity, shear-thinning, and thixotropy in defining the “printability window” of dental resins and explores the relationship between these properties and the formulation and final material performance. Rheological characterization using rotational rheometry provides key insights, with shear rate sweeps and thixotropy tests quantifying whether a resin behaves as Newtonian or pseudoplastic. The literature shows that optimal printability typically requires resins with low to moderate viscosity at shear, moderate thixotropy for stability, and formulations balanced between high-strength oligomers and low-viscosity diluents. The addition of fillers modifies the viscosity and dispersion, which can improve reinforcement but may reduce print resolution if not optimized. Thermal and optical considerations are also coupled with rheology, affecting the curing depth and accuracy. In conclusion, controlling resin rheology is essential for bridging material formulation with reliable clinical outcomes, guiding both resin design and printer process optimization in modern dental applications. Full article

This study investigates the mechanical behavior of water-washable photosensitive resins used in masked stereolithography (mSLA) 3D printing, evaluating the effect of post-curing time (0, 5, 10, 30, and 60 min) and printing orientation (Flat [XY], Vertical [Z], and On-edge [XZ]) on the material characteristics. Specimens were manufactured according to ISO 527-2 type 1B and ISO 178 standards for tensile and bending tests, respectively. A Matlab algorithm was developed to automate the processing of experimental data. This tool enabled the extraction of parameters to fit distinct mathematical models for the elastic (linear) and nonlinear (polynomial) regimes, allowing the material response to be characterized at different curing times and print orientations. These models were implemented in Ansys Workbench for comparison with experimental results. The results show that increasing the post-curing time from 0 to 60 min raises the elastic modulus from 964.5 to 1892.4 MPa in the Flat [XY] orientation and from 774 to 1661.2 MPa in the Vertical [Z] orientation for tensile testing. In bending testing, the Flat [XY] orientation presented the best mechanical properties, while the Vertical [Z] and On-edge [XZ] orientations showed similar behavior. The numerical simulations adequately reproduced the experimental results, validating the developed constitutive models. Finally, a stress–strain correlation model is presented that enables estimation for any post-curing time between 0 and 60 min. This study provides essential data for optimizing 3D printing processes and developing structural applications with photopolymer resins. Full article

This study examines the influence of different printing orientations and infill settings on the strength and flexibility of components produced using resin-based 3D printing, particularly with masked stereolithography (MSLA). Using a common photopolymer resin and a widely available desktop MSLA printer, we produced and tested a series of samples with varying tilt angles and internal structures. To understand their mechanical behavior, we applied a custom bending test combined with high-precision deformation tracking through the GOM ARAMIS digital image correlation system. The results obtained clearly show that both the angle of printing and the density of the internal infill structure play a significant role in how much strain the printed parts can handle before breaking. Notably, a 75° orientation provided the best deformation performance, and infill rates between 60% and 90% offered a good balance between strength and material efficiency. These findings highlight how adjusting print settings can lead to stronger parts while also saving time and resources—an important consideration for practical applications in engineering, design, and manufacturing. Full article

The article presents a three-stage methodology for calibrating 3D printing using mSLA technology, aimed at improving dimensional accuracy and print repeatability. The proposed approach is based on procedures that enable the collection and analysis of numerical data, thereby minimizing the influence of the operator’s subjective judgment, which is commonly relied upon in traditional calibration methods. In the first stage, compensation for the uneven illumination of the LCD matrix was performed by establishing a regression model that describes the relationship between UV radiation intensity and pixel brightness. Based on this model, a grayscale correction mask was developed. The second stage focused on determining the optimal exposure time, based on its effect on dimensional accuracy, detail reproduction, and model strength. The optimal exposure time is defined as the duration that provides the highest possible mechanical strength without significant loss of detail due to the light bleed phenomenon (i.e., diffusion of UV radiation beyond the mask edge). In the third stage, scale correction was applied to compensate for shrinkage and geometric distortions, further reducing the impact of light bleed on the dimensional fidelity of printed components. The proposed methodology was validated using an Anycubic Photon M3 Premium printer with Anycubic ABS-Like Resin Pro 2.0. Compensating for light intensity variation reduced the original standard deviation from 0.26 to 0.17 mW/cm², corresponding to a decrease of more than one third. The methodology reduced surface displacement due to shrinkage from 0.044% to 0.003%, and the residual internal dimensional error from 0.159 mm to 0.017 mm (a 72% reduction). Full article