Search Results (113)

The nanoscale surface topography and microhardness of additive and subtractive dental polymers were evaluated following exposure to environmental challenges. The study examined two 3D-printed resins (Saremco and Voco) and two milled CAD/CAM blocks (Vita Enamic and Tetric). Specimens were allocated to control or experimental groups and subjected to hydrothermal ageing (thermocycling), in vitro mechanical wear, or a combined protocol involving wear followed by thermal ageing. Surface microtopography was analysed both quantitatively and qualitatively using atomic force microscopy (AFM), while structural stability was assessed through surface microhardness testing. Statistical significance was determined using matrix comparisons (p < 0.05). Milled monolithic blocks demonstrated a dense, uniform baseline topography, whereas 3D-printed resins exhibited structural heterogeneity attributed to their layer-by-layer photocuring process. Saremco maintained polymer network stability under thermal stress (p = 0.1878), while Voco was highly susceptible to hydrothermal swelling and early matrix plasticization (p = 0.0084). The combined protocol of wear and thermal ageing resulted in advanced structural breakdown in all groups (p < 0.001). Industrial subtractive blocks exhibited greater resistance to oral environmental stresses. The ceramic framework of Vita Enamic limited polymer domain collapse, whereas Tetric experienced accelerated inter-layer delamination and embrittlement. The combined protocol of wear followed by thermal ageing resulted in significant and uniform degradation of surface microhardness and topographic roughness in all tested groups. Nevertheless, the additively manufactured resins demonstrated substantial structural integrity and exhibited low volumetric wear rates. Full article

Glass-transition-driven shape memory polymers are promising materials for 4D printing because their thermally activated transition enables programmed deformation and recovery without relying on melting or crystallization-driven switching. In this study, PDMS-MMA-modified photocurable networks were designed for vat photopolymerization-based 4D printing by varying PDMS-MMA content and switching monomer structure while maintaining a fixed TMPTMA crosslinker content. The resin formulations were prepared using tert-butyl acrylate (tBA) or isobornyl acrylate (IBOA) as switching monomers, PDMS-MMA as a flexible mobility-regulating segment, and TMPTMA as a multifunctional crosslinker. The effects of formulation composition on printability, network formation, thermal stability, thermomechanical transition, mechanical properties, and shape memory behavior were systematically investigated. FT-IR analysis confirmed effective photocuring of the acrylate/methacrylate networks, while rheological evaluation showed that resin viscosity depended on monomer structure and PDMS-MMA content. DMA results revealed thermomechanical transition, although some formulations exhibited broad tan δ responses due to network heterogeneity and distributed segmental relaxation. Based on resin printability, printed-part resolution, and relatively well-defined tan δ transitions, T-15 and I-15 were selected as representative formulations for quantitative shape memory evaluation. Shape memory testing was conducted under force-control mode because stable strain-controlled programming was not achievable for the printed specimens. Both T-15 and I-15 exhibited high shape fixity over two programming–recovery cycles. I-15 showed stable recovery behavior with recovery ratios of 91.51% and 95.87%, whereas T-15 showed apparent over-recovery with recovery ratios exceeding 100%, likely due to residual stress release during reheating. Overall, these results demonstrate that thermally activated shape-memory performance is governed not only by the nominal transition temperature but also by the coupled effects of PDMS-mediated segmental mobility, switching monomer structure, mechanical integrity, and elastic energy storage within a fixed crosslinked network framework. Full article

Conventional photocurable resins suffer from low mechanical strength and poor thermal stability, which restrict their broader application in photopolymerization-based 3D printing technologies. Strategies such as inorganic fillers or interpenetrating polymer networks (IPNs) improve performance but often lead to high viscosity or long post-curing times. In this work, a high-performance photocurable resin system based on tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA) and N, N-dimethylacrylamide (DMAA) was developed, achieving low viscosity and direct room-temperature 3D printability. Partial substitution of DMAA with Tricyclodecanedimethanol diacrylate (DCPDA) further enhanced its mechanical and thermal properties. The optimized resin exhibited a tensile strength of 80.9 MPa, a flexural strength of 166.1 MPa, a glass transition temperature of 176.2 °C, and a low viscosity of 78.7 mPa·s with shrinkage below 10%. The heat deflection temperatures reached 168.1 °C under 1.80 MPa and 187.3 °C under 0.45 MPa. This study provides an effective strategy for developing high-strength and heat-resistant photocurable resins suitable for efficient room-temperature 3D printing applications. Full article

The present study addresses the fabrication of porous gyroid architectures by additive manufacturing from preceramic polymer feedstocks. Photocurable emulsions were engineered by combining a silicone powder with acrylate monomers and dispersing an emulsified secondary phase of calcium nitrate. The formulations showed light-curing behaviour compatible with digital light processing vat photopolymerization (DLP-VPP), enabling high-fidelity replication of triply periodic minimal surface (TPMS) gyroids (designed porosity: 85 vol.%). After pyrolysis in nitrogen at 700 °C, the lattices converted into CaO–SiO₂-derived amorphous matrices embedding an in situ turbostratic/pyrolytic carbon fraction, as suggested by the photothermal response and preliminary impedance behaviour, although the latter was measured in liquid electrolyte and therefore does not isolate electronic transport. To improve robustness during polymer-to-ceramic conversion, pharmaceutical borosilicate waste glass (BASG) was added as a passive filler (30–70 wt.%). The waste-glass phase acts as a passive filler that improves processing robustness and can mitigate shrinkage-induced damage during pyrolysis, while remaining electrically insulating (dielectric) and therefore not directly contributing to electronic conduction. The resulting structures combine high surface-to-volume ratio, controlled open porosity, and structural integrity with electrochemical responsiveness under the adopted test conditions, making them promising architected platforms for electrochemical components where interconnected porosity is advantageous. Full article

The synthesis of reactive sucrose derivatives is of significant interest for the development of novel biocompatible polymers. In this study, an octa-substituted sucrose derivative containing isocyanate groups was synthesized via a urethane-forming reaction carried out in an aprotic solvent at the phase interface. This approach exhibits high selectivity and provides a target product yield of up to 60%. Subsequently, using the same reaction mechanism, the isocyanate derivative was converted into an octa-functional methacrylate derivative capable of forming three-dimensional cross-linked networks. The structures of both the intermediate and final products were confirmed by IR, ¹H NMR, and mass spectrometry. The sucrose-based prepolymer was further evaluated in the formation of cross-linked structures for potential application as bone-substituting implants. Using various photocuring techniques, including two-photon 3D printing, both plates and microstructured scaffolds were fabricated. These structures exhibited high thermal stability, elastic properties comparable to those of bone tissue, and no toxic effects on cells. Full article

Nanogrooves provide instructive cues to cells in culture. Several nanofabrication techniques have been developed to create biomimetic substrates, advancing our understanding of cell adhesion. Their integration into nervous system models highlights the critical role of the extracellular matrix (ECM) in developing functional tissue constructs for in vitro platforms such as Brain-on-Chip (BoC) and Nervous System-on-Chip (NoC). This study presents a nanofabrication approach that integrates photolithography and microtransfer molding (μTM) to pattern nanogrooves using photocurable polymer NOA81 onto microelectrode array (MEA) plates. The resulting nanogrooves exhibited a pattern periodicity of 976 nm and a ridge width of 232 nm, as confirmed by scanning electron microscopy and atomic force microscopy. We assessed the biocompatibility and functional impact of these modified substrates using human induced pluripotent stem cell (hiPSC)-derived neuronal cultures. Neurons cultured on nanogroove-modified MEAs exhibited aligned neural processes due to the anisotropic surface features and expressed vivid spiking behavior and higher burst frequency compared to randomly cultured neuronal networks. In conclusion, the proposed fabrication technique integrates nanogrooves with commercial MEAs using a combination of microtransfer molding and photolithography, resulting in modified culture substrates that enhance spike activity and network organization, aiding in the development of more in vivo-like neural models. Full article

Hybrid metal–polymer components are used in many industries, such as in aerospace, automotives, and electronics, due to the possibility of reducing the weight of the final part while maintaining mechanical properties comparable to components made entirely of metal. Conventional 3D printing processes do not enable the direct fabrication of hybrid structures consisting of solid metal and polymer parts due to the significant differences in the processing temperatures of both materials. A solution to this problem is the integration of two processes, electrodeposition and photopolymerization, which allow fabrication to be carried out at room temperature. This paper presents preparatory studies aimed at developing a new 3D printing technology that uses the simultaneous application of electrodeposition and photopolymerization to manufacture hybrid metal–polymer elements in a single, integrated 3D printing process. Here, a hybrid metal–polymer element is defined as a component composed of at least two bonded parts, including at least one metal part fabricated by electrodeposition and at least one polymer part produced by photopolymerization. Thus, it is not a polymer component merely coated with an electrodeposited metal layer, but a true hybrid structure consisting of functional metallic and polymeric parts. Such components can be manufactured using the world’s first hybrid 3D printer, which integrates electrodeposition and photopolymerization to produce metal–polymer hybrid parts within a single 3D printing process (the device has been submitted to the Polish Patent Office). However, its design and operating principle are beyond the scope of this paper. The presented research focuses on initial study of selected feedstock materials for this printer, namely photocurable resins and electroplating baths. Since the entire hybrid printing process occurs in an electroplating bath environment, studies of these materials for 3D printing under such conditions were essential. This work includes a screening study of photocurable formulations with respect to rheological properties, 3D printing tests in a model copper electroplating bath, and selection of a suitable bath brightener to maximize the quality (fine grain size, homogeneous grain distribution) of additively deposited copper layers. The study was conducted using copper electrodeposition and acrylate resin photopolymerization as model processes for evaluating the proposed hybrid metal–polymer 3D printing technology. Finally, the most suitable feedstock materials for producing metal–polymer hybrid parts via the proposed 3D printing method were selected. Full article

A photo-curable silicone-modified resin system based on polydimethylsiloxane (PDMS) was developed and systematically evaluated for stereolithography (SLA)-based 3D printing applications. The resin formulation consisted of bisphenol A ethoxylate dimethacrylate (Bis-EMA) and trimethylolpropane triacrylate (TMPTMA) as reactive monomers, with methacrylate-terminated PDMS (PDMS-MMA) incorporated at concentrations ranging from 0 to 15 wt%. The influence of PDMS-MMA content on key physicochemical properties relevant to SLA processing, including viscosity, mechanical performance, thermal stability, optical transmittance, and curing shrinkage, was systematically investigated. Moderate incorporation of PDMS-MMA improved the mechanical flexibility of the resin, with the tensile strength reaching a maximum value of 5.95 MPa at 5 wt% PDMS-MMA. However, further increases in PDMS-MMA content resulted in a gradual decrease in tensile strength and optical transmittance, indicating the importance of optimizing the formulation composition. Thermogravimetric analysis (TGA) indicated improved thermal stability with increasing PDMS-MMA content, while curing shrinkage decreased progressively as the PDMS fraction increased. Structural printing tests confirmed that the developed resin system exhibited stable layer adhesion and shape fidelity during SLA fabrication, enabling the successful printing of complex three-dimensional structures. These results demonstrate that PDMS-modified acrylate resins provide a promising strategy for balancing mechanical flexibility, dimensional stability, and printability in SLA-based additive manufacturing. Full article

The orthodontic landscape is currently witnessing a significant technological evolution with the emergence of direct 3D-printed aligners (DPAs), which promise to close the digital workflow loop by eliminating the geometric limitations and solid model waste inherent to traditional thermoformed clear aligners (TCAs). This review provides a comprehensive analysis of the material science governing this transition from inert thermoplastic sheets to reactive photocurable resins. We explore the fundamental chemistry of DPA materials, and the pivotal role of post-processing in ensuring mechanical integrity and biocompatibility. Beyond passive mechanics, this review highlights preclinical research in functional material engineering, detailing how experimental DPAs are being investigated for the integration of antibacterial agents, remineralization fillers, and drug delivery systems. Furthermore, we evaluate the limited but emerging clinical data on DPAs, contrasting their shape-memory properties and force delivery profiles with conventional appliances, while critically addressing emerging safety concerns regarding monomer elution and microplastic generation. We conclude that while DPA technology offers superior dimensional control, comprehensive life cycle assessments and long-term in vivo trials are essential to fully substantiate their clinical efficacy, overall sustainability, and potential as advanced orthodontic appliances. Full article

There are limited material choices for vat photopolymerization additive manufacturing processes that offer high dimensional accuracy. Acrylates and epoxies are commonly used, but their thermal properties are not suitable for applications requiring high-temperature performance. A possible solution is the use of high-performance thermosets, such as maleimide and cyanate ester, which are cured at high temperatures. Still, their use in vat photopolymerization methods has been limited due to the high temperature required. In this work, a photocurable formulation composed of multimaleimide monomers, a reactive diluent, and a cyanate ester was developed to improve thermal and mechanical properties and reduce cure shrinkage due to density changes during processing. In situ sequential interpenetrating polymer networks (IPNs) were investigated, in which the copolymerization of multimaleimide and a diluent occurs during printing, yielding a cyanate ester-swollen network with a sub-room-temperature glass transition temperature (T_g). The polymerization of the cyanate ester occurs during a high-temperature post-printing step. The resulting materials have a T_g above 250 °C (peak in the loss modulus), good fracture toughness (GIc of 100 J/m²), and overall cure shrinkage of less than 6%, with 1–2% occurring during the high-temperature post-curing step. Full article

Choline salts represent sustainable and safe electrolyte systems. In this study, an aqueous 1 M choline nitrate solution was employed to prepare hydrogel polymer electrolytes (HPE) via in situ photopolymerization. To enhance compatibility between the electrolyte and polymer matrix, choline methacrylate was synthesized and used as a functional monomer alongside HEMA and PEGDA. The photocurable formulation contained 70 wt.% electrolyte and 30 wt.% monomer mixture. Subsequent electrolyte uptake increased the electrolyte fraction in the HPE to 87 wt.%. The use of choline methacrylate enabled the formation of transparent HPE with favorable mechanical performance, showing puncture resistance of 0.33 N and 0.28 N at elongations of 7.9 mm and 4.4 mm for samples with 70 and 87 wt.% electrolyte, respectively. High ionic conductivity was achieved, reaching ~18 mS/cm and ~34 mS/cm for HPE with 70 and 87 wt.% electrolyte. Finally, a capacitor assembled with HPE containing 87 wt.% electrolyte demonstrated good operational parameters, confirming the applicability of this system in energy storage devices. This work highlights the potential of choline-based electrolytes and polymerizable choline derivatives as functional components for the design of efficient, safe, and environmentally friendly gel polymer electrolytes. Full article

Laminated polymer composites have emerged as a promising class of materials that provide exceptional mechanical and functional properties owing to multilayered architectures. In addition, additive manufacturing (AM) offers boundless opportunities to fabricate complex and intricate geometries with a wide variety of materials. Utilizing AM processes for producing laminated polymer composites can open new pathways for producing these intricate structures with fine control over geometry, layer thickness, and material distribution. In this study, we demonstrate the use of the stereolithography (SLA) process to fabricate laminated polymer composites to overcome the limitations of extrusion-based AM processes, i.e., challenges in high precision, strong interlayer bonding and uniform particle distribution. Photocurable polymer composites were prepared by adding different reinforcing particles, i.e., cobalt iron oxide (CoFe₂O₄), graphene (G), magnesium (Mg) and iron (II,III) oxide (Fe₃O₄), into the photocurable resin. Ultrasonication and mechanical mixing processes were used to prepare stable photocurable composites suitable for the SLA process. SLA process was also optimized, varying the process parameters (exposure time, bottom exposure time and bottom layer count) to achieve optimum dimensional accuracy and surface quality. Microscopic analysis confirmed the distinct and well-adhered composite layer sandwiched between the unfilled resin, validating the structural integrity of the multilayer design. Mechanical testing revealed significant improvement in the tensile properties of the laminated composites compared to pure resin, with resin/CoFe₂O₄ exhibiting 35.6% and 50.1% improvement in tensile strength and Young’s modulus compared to the pure resin, respectively. These results highlight the feasibility of SLA for producing multilayered polymer composites with improved mechanical performance and controlled architecture, broadening its potential for advanced engineering and biomedical applications. Full article

Digital light processing (DLP) 3D printing is a powerful additive manufacturing technique but is limited by the relatively low mechanical strength of cured neat resin parts. In this study, a renewable bio-adhesive lignin was introduced as a reinforcing filler into a bisphenol A-type epoxy acrylate (EA) photocurable resin to enhance the mechanical performance of DLP-printed components. Lignin was incorporated at low concentrations (0–0.5 wt%), and three dispersion methods—magnetic stirring, planetary mixing, and ultrasonication—were compared to optimize the filler distribution. Cure depth tests and optical microscopy confirmed that ultrasonication (40 kHz, 5 h) achieved the most homogeneous dispersion, yielding a cure depth nearly matching that of the neat resin. DLP printing of tensile specimens demonstrated that as little as 0.025 wt% lignin increased tensile strength by ~39% (from 44.9 MPa to 62.2 MPa) compared to the neat resin, while maintaining similar elongation at break. Surface hardness also improved by over 40% at this optimal lignin content. However, higher lignin loadings (≥0.05 wt%) led to particle agglomeration, resulting in diminished mechanical gains and impaired printability (e.g., distortion and incomplete curing at 1 wt%). Fractographic analysis of broken specimens revealed that well-dispersed lignin particles act to deflect and hinder crack propagation, thereby enhancing fracture resistance. Overall, this work demonstrates a simple and sustainable approach to reinforce DLP 3D-printed polymers using biopolymer lignin, achieving significant improvements in mechanical properties while highlighting the value of bio-derived additives for advanced photopolymer 3D printing applications. Full article

The article presents the results of a study of the possibility of using heat-treated ethylene-vinyl acetate copolymer (EVA) as a thermoplastic modifier in a photosensitive composition based on tert-butyl acrylate (tBA). The use of such a modifier in 3D printing compositions is important for improving their physical and mechanical properties at low temperatures. An attempt was also made to use EVA as a polymer chain brancher. The molecular structure of the components and their compositions, rheology, curing kinetics, and phase organization of photocured systems were studied using FTIR and NMR spectroscopy, spectrophotometry, rheometry, Photo-DSC, and scanning electron microscopy. It was found that heat treatment of EVA allows the formation of single C=C bonds in macromolecules, which are necessary for a potential crosslinking agent with tBA. It was shown that EVA effectively functions as a thickener and modifier: with an increase in the modifier concentration, the nature of the composition flow changes from Newtonian to pseudoplastic, the rate of the photochemical polymerization reaction decreases, and the degree of conversion of the system decreases. However, the formation of a heterogeneous phase structure and the absence of a continuous spatial network of chemical bonds prevent the use of EVA simultaneously as a functional additive and crosslinking agent. Full article

The Na₂O-SrO-SiO₂ system shows promise in the development of glasses that can be transformed into electrically conductive glass ceramics. The conventional processing of such materials usually involves the synthesis of a parent glass, followed by a complex devitrification treatment. This study proposes a simplified approach based on the use of preceramic polymers, namely silicone resins combined with oxide fillers. These systems yield silicate-based ceramics through direct heat treatment, replicating the phase assembly of traditional glass ceramics with no need for prior glass melting. A printable formulation was developed by mixing a silicone resin with an acrylate-based photocurable resin, sodium nitrate and strontium carbonate. The resulting ‘suspension-emulsion’ was later shaped into monolithic components using digital light processing. After pyrolysis in nitrogen atmosphere, the components transformed into SrSiO₃ crystals embedded in a composite matrix, in turn composed of glass and turbostratic carbon (the latter specifically offered by the silicone polymer). This combination of crystalline silicates and carbon resulted in measurable electrical conductivity. This study confirms that silicone-derived systems can serve as effective precursors for conductive glass-ceramic analogues, providing an alternative to conventional methods with single-step processing. This approach enables structural shaping through 3D printing and the development of functional properties suitable for electronic or electrochemical applications. Full article