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Photocurable materials offer a rapid transition from a liquid to a solid state, and have recently received great interest in the medical field. However, while dental resins are very popular, only a few materials have been developed for soft tissue repair. This study aims to synthesize a difunctional methacrylate monomer using a dibutyltin dilaurate which is suitable for the photocuring of soft materials. These soft materials were compared with PhotoBioCure® (Szczecin, Poland) material with a similar molecular weight, of Mn ~7000 g/mol on average. Infrared spectroscopy was used to monitor the two-step synthesis catalyzed with dibutyltin dilaurate, while spectroscopic and chromatographic methods were used to determine the chemical structure and molecular weight of the monomers. Photopolymerization kinetics under varying light intensities were explored in a nitrogen atmosphere for representative difunctional monomers. The mechanical testing of the resulting elastomeric films confirmed tensile strength and modulus values consistent with soft tissue parameters in the range of 3–4 MPa. The 3D printability of the macromonomers was also assessed. Additionally, cytotoxicity assessments using cultured cells showed a high cell viability (97%) for all new materials. Overall, we demonstrate that difunctional methacrylate monomers converted to flexible solids during photopolymerization show great potential for biomedical applications. [ABSTRACT FROM AUTHOR]

Background: Gold nanoparticles can generate heat upon exposure to radiation due to their plasmonic properties, which depend on particle size and shape. This enables precise control over the release of active substances from polymeric pharmaceutical formulations, minimizing side effects and premature release. The technology of 3D printing, especially vat photopolymerization, is valuable for integrating nanoparticles into complex formulations. Method: This study aimed to incorporate gold nanospheres (AuNSs) and nanorods (AuNRs) into polymeric matrices using vat photopolymerization, allowing for controlled drug release with exposure to 532 nm and 1064 nm wavelengths. Results: The AuNSs (27 nm) responded to 532 nm and the NRs (60 nm length, 10 nm width) responded to 1064 nm. Niclosamide was used as the drug model. Ternary blends of Polyethylene Glycol Diacrylate 250 (PEGDA 250), Polyethylene Glycol 400 (PEG 400), and water were optimized using DesignExpert 11 software for controlled drug release upon specific wavelength exposure. Three matrices, selected based on solubility and printability, underwent rigorous characterization. Two materials achieved controlled drug release with specific wavelengths. Bilayer devices combining AuNSs and AuNRs demonstrated selective drug release based on irradiation wavelength. Conclusions: A pharmaceutical device was developed, capable of controlling drug release upon irradiation, with potential applications in treatments requiring delayed administration. [ABSTRACT FROM AUTHOR]

The article discusses the integration of 3D printing technology into chemistry lessons, highlighting its benefits in creating high-quality teaching materials and educational games at a lower cost. It explores the use of 3D printing as a learning tool to understand plastics and resin printers, promoting digital skills relevant for teachers and students. The article also delves into the process of creating 3D-printed objects and the chemical background of resin printing, focusing on the application of radical polymerization in the classroom. [Extracted from the article]

Solvent‐free photopolymerization of vinyl monomers to produce high modulus materials with applications in 3D printing and photoswitchable materials is demonstrated. Polymerizable eutectic (PE) mixtures are prepared by simply heating and stirring various molar ratios of N‐isopropylacrylamide (NIPAM), acrylamide (AAm) and 2‐hydroxyethyl methacrylate (HEMA). The structural and thermal properties of the resulting mixtures are evaluated by 1D and 2D NMR spectroscopy as well as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). UV photocuring kinetics of the PE mixtures is evaluated via in situ photo‐DSC and photorheology measurements. The PE mixtures cure rapidly and display storage moduli that are orders of magnitude greater than equivalent copolymers cured in an aqueous medium. The versatility of these PE systems is demonstrated through the addition of a photoswitchable spiropyran acrylate monomer, as well as applying the PE formulation as a stereolithography (SLA)‐based 3D printing resin. Due to the hydrogen‐bonding network in PE systems, 3D printing of the eutectic resin is possible in the absence of crosslinkers. The addition of a RAFT agent to reduce average polymer chain length enables 3D printing of materials which retain their shape and can be dissolved on demand in appropriate solvents. [ABSTRACT FROM AUTHOR]

This work aimed to redesign a personalized prototype of an external breast prosthesis using additive manufacturing technology. The primary objective was to develop a prosthesis capable of closely simulating the deformation characteristics of a natural breast while adhering to the principles of Hooke's law and being able to withstand the pressures exerted by typical bras. To achieve this, a detailed 3D scan of a volunteer's breast was employed as the foundation for the prosthesis model. Multiple prototypes were crafted, each utilizing a gyroid structure with varying fill percentages, including 5%, 7.5%, 10%, and 25%. Comprehensive compression tests were conducted following ASTM D1621 standards. The results indicated that the 7.5% fill percentage prototype exhibited superior deformation properties under less applied pressure. Furthermore, extensive design evaluations were conducted to optimize 3D printing parameters and minimize the need for internal printed supports. This work underscores the potential of additive manufacturing as a promising technique for producing external breast prostheses that offer functional support and prioritize comfort and natural aesthetics. [ABSTRACT FROM AUTHOR]

Hydrogels have revolutionized the field of soft robotics with their ability to provide dynamic and programmable responses to different stimuli, enabling the fabrication of highly adaptable and flexible robots. This continual development holds significant promise for applications in biomedical devices, active implants, and sensors due to the biocompatibility of hydrogels. Actuation in hydrogel-based soft robotics relies on variations in material properties, structural design, or a combination of both to generate desired movements and behaviors. While such traditional approaches enable hydrogel actuation, they often rely on complex material design, bringing challenges to hydrogel fabrication and hindering practical use. Therefore, this work seeks to present a simplified and versatile approach for fabricating programmable single-component hydrogel-based soft robotics using an encoded building block design concept and 3D printing. A series of structural building blocks have been designed to achieve various actuation characteristics, including the direction, degree, and kinetics of actuation. By assembling these building blocks into various configurations, a broader range of actuation responses can be encoded, allowing for the fabrication of versatile, programmable soft robotics using a single uniform material through vat photopolymerization 3D printing. This approach enables adaptation to a wide range of applications, providing highly customizable encoding designs. [ABSTRACT FROM AUTHOR]

Sulfur dots (S‐dots) eliminate the need of expensive and toxic conventional photocatalysts or transition metal in photoinduced reversible deactivation radical polymerization (photoRDRP). Herein, non‐metallic S‐dots mediated photoRDRP of N,N‐dimethyl acrylamide (DMA) are developed for the first time. This technique allows for the precise synthesis of narrow‐dispersed poly(N,N‐dimethyl acrylamide) (PDMA) and double hydrophilic poly(N, N‐dimethyl acrylamide)‐block‐poly(2‐hydroxyethyl acrylamide) (PDMA‐b‐PHEAA) diblock copolymer suitable for contaminant removal from water. Also, its subsequent modification into a poly(N,N‐dimethyl acrylamide)‐block‐poly(N‐(2‐((4‐vinylbenzyl)oxy)ethyl)acrylamide) (PDMA‐b‐PVBEAA) diblock copolymer gives ultra‐fast gelation and production of writable ink‐gel, which is exceptionally well‐suited for 3D printing applications, enabling the creation of precise and defined shapes. This innovative material serves as an intriguing scaffold for tissue engineering and other biomaterial applications, especially in areas that demand rapid and customizable manufacturing solutions. [ABSTRACT FROM AUTHOR]

In order to improve the performance of polymer-derived ceramics and expand its application field, the formulation of the photosensitive resin was further optimized and on the basis of modification, the two-dimensional filler h -BN was introduced in this paper. It was found that both the content of PVSA in the photosensitive resin and the introduction of h -BN had remarkable impacts on the properties of the polymer-derived ceramics. When the h -BN content in the PVSA photosensitive resin was 1 wt%, the bending strength and fracture toughness of the ceramic sample after pyrolysis reached 252.4 ± 12.2 MPa and 2.7 ± 0.2 MPa·m1/2, respectively. With the increase of h -BN content, the thermal conductivity of the composite ceramics increased from 0.44 W·m−1·K−1 to 5.34 W·m−1·K−1. It is concluded that the thermal, electrical, and mechanical properties of precursor ceramics are improved by the introduction of two-dimensional fillers of h -BN. [ABSTRACT FROM AUTHOR]

Purpose: This article aims to present an overview of additive manufacturing technologies, including the latest research trends and a heuristic comparative analysis of the selected technologies group. Design/methodology/approach: Quantitative analysis of research articles from the past 5 years was performed using the most referred scientific databases - Scopus and Web of Science. Qualitative analysis included a State-of-the-Art overview of 3D printing by means of photopolymerization, material and binder jetting, extrusion techniques and powder fusion. Heuristic comparative analysis of the abovementioned technologies was performed using a dendrological matrix, considering the potential and attractiveness traits of the listed methods. Findings: The quantitative analysis results indicate that powder fusion technologies have received the most attention in the last 5 years. Heuristic procedural benchmarking analysis has found that Powder Bed Fusion is the most promising group of additive manufacturing technologies. Research limitations/implications: Presented review indicates that industrial applications of additive manufacturing are continuously growing, compared to other manufacturing technologies, such as casting, forming and subtractive treatment. The upward trend is expected to continue in the near future, and the range of practical industrial applications will expand rapidly. Practical implications: The quantitative, qualitative, and comparative analysis of additive manufacturing technologies presented in this article might be useful for researchers looking for interesting new research areas. The same applies to entrepreneurs interested in implementing modern additive manufacturing techniques in business practice. Originality/value: The value of this paper is the presentation of a wide spectrum of additive manufacturing technologies using various technical solutions and engineering materials, considering the latest development trends in their area. [ABSTRACT FROM AUTHOR]

Today, controlling the photopolymerization process during the 3D printing in vat photopolymerization is a key challenge. In this work, it is shown that using a relatively limited set of parameter, it is possible to estimate key factors involved in such process. On the basis of 16 formulations containing different concentrations of photoinitiator and UV filter, attempt was made to rationalize the photonic parameters used in the 3D printing process, that is, the depth of penetration Dp and the critical energy Ec. It is shown that the experimental Dp values can be correlated with calculated ones from Bouguer–Beer–Lambert law. Real‐time Fourier‐transform infrared spectroscopy (RT‐FTIR) experiments were performed under similar conditions as in 3D printing. The conversion profiles were used to estimate the Ec values. The limits of this approach was discussed as a function of the UV filter concentration. Finally, the RT‐FTIR curves are exploited to predict the in‐depth conversion of the different 3D printed layers and compared to experimental results obtained by confocal Raman microscopy. [ABSTRACT FROM AUTHOR]

3D printing technology provides new ways to complex-shaped ceramic cores forming inner structures in aero-engine blades, but its high-temperature dimensional accuracy is highly impacted by their volume shrinkage and creep deformation. Silica ceramic cores reinforced by mullite fibers were fabricated by 3D printing in terms of vat photopolymerization in this work. Due to the scraper paving the ceramic slurry in 3D printing, majority of the mullite fibers displayed orientation distribution inside the printing layers and decreased the bending strength as the fiber content was below 5 wt%. With 12.5 wt% of mullite fibers, some fibers showed disorder distribution and arranged to connect the interlayer cracks, therefore improving the strength by fiber pull-out. Even though the reinforcement effect of mullite fibers was inadequate, the porosity and leaching rate were significantly improved. Furthermore, the mullite fibers were beneficial to lower shrinkage during sintering and casting, and enhanced the creep resistance due to the high softening temperature, which resulted in enhanced dimensional accuracy. [ABSTRACT FROM AUTHOR]

Vat photopolymerization (VP) additive manufacturing enables fabrication of complex 3D objects by using light to selectively cure a liquid resin. Developed in the 1980s, this technique initially had few practical applications due to limitations in print speed and final part material properties. In the four decades since the inception of VP, the field has matured substantially due to simultaneous advances in light delivery, interface design, and materials chemistry. Today, VP materials are used in a variety of practical applications and are produced at industrial scale. In this perspective, we trace the developments that enabled this printing revolution by focusing on the enabling themes of light, interfaces, and materials. We focus on these fundamentals as they relate to continuous liquid interface production (CLIP), but provide context for the broader VP field. We identify the fundamental physics of the printing process and the key breakthroughs that have enabled faster and higher-resolution printing, as well as production of better materials. We show examples of how in situ print process monitoring methods such as optical coherence tomography can drastically improve our understanding of the print process. Finally, we highlight areas of recent development such as multimaterial printing and inorganic material printing that represent the next frontiers in VP methods. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to address the challenge of reducing the build time of a fused deposition modeling (FDM) system while maintaining part strength, proposing a hybrid technique combining photopolymerization and FDM. Design/methodology/approach: For developing the hybrid system, a standard FDM machine was modified to incorporate necessary components so that the whole system can be operated with a single interface; further, the samples were fabricated with conventional and modified process to evaluate the efficacy of the developed system, to determine the extent of time reduction that the proposed methodology can obtain, additionally different sort of 3D models were selected and their build time was compared. Findings: The modified hybrid mechanism can successfully fabricate parts with a modified G-code. The simulation of the technique shows that a reduction of 34%–87% can be achieved for simpler models such as cube while a reduction ranging from 30.6%–87.8% was observed for complex models. An increase in strength of 6.58%, 11.51% and 37.32% was observed in X, Y and Z directions, along with a significant increase in toughness as compared with FDM parts for parts fabricated with the developed mechanism. Practical implications: The modified mechanism could be used for fast fabrication purposes, which could be very useful for serving situations such as emergency health care, rapid tooling. Originality/value: This research contributes a novel hybrid technique for additive manufacturing, offering a substantial reduction in build time without compromising mechanical properties, even increasing them. [ABSTRACT FROM AUTHOR]

Contact lenses are widely used for vision correction and cosmetic purposes. Smart contact lenses offer further opportunities as functionalized non-invasive devices capable of simultaneous vision correction, real-time health monitoring and patient specific drug delivery. Herein, a low-cost vat photopolymerization technique is developed for directly 3D printing functionalized structures on commercially available contact lenses. The process enables controlled deposition of functionalized hydrogels, in customizable patterns, on the commercial contact lens surface with negligible optical losses. Multi-functional contact lenses can also be 3D printed with multiple materials deposited at different regions of the contact lens. Herein, the functionalities of colour blindness correction and real-time UV monitoring are demonstrated, by employing three suitable dyes incorporated into 2-hydroxyethyl methacrylate (HEMA) hydrogel structures printed on contact lenses. The results suggest that 3D printing can pave the way towards simple production of low-cost patient specific smart contact lenses. [ABSTRACT FROM AUTHOR]

Light‐mediated 3D printing techniques have gained significant interest due to the inherent advantages of light as external stimuli, including spatiotemporal control and easy access. As 3D printing processes require rapid polymerization, free radical or cationic polymerization methods are used. However, these polymerization reactions are limited to the production of materials with properties that cannot be chemically altered post‐printing. In this work, a rapid, open‐to‐air photo‐controlled cationic reversible addition‐fragmentation chain‐transfer polymerization of vinyl ethers is demonstrated in the presence of a three‐component photoinitiating system comprising a photosensitizer, electron donor, and acceptor as co‐initiators under the irradiation with blue light. The polymerization mechanism shows rapid kinetics and controlled, living polymerization characteristics. Trithiocarbonate chain ends of poly(isobutyl vinyl ethers) are reactivated to produce block copolymers with cyclohexyl vinyl ethers. The rapid kinetics and water tolerance of the reported system enable the 3D printing of polymeric solids under ambient (e.g., room temperature and open to air) conditions, followed by the effective reactivation of trithiocarbonate chain ends to post‐synthetically modify the object with an acrylate‐based fluorescent monomer via a controlled radical polymerization strategy. [ABSTRACT FROM AUTHOR]

The additive manufacturing (AM) industry increasingly looks to differentiate itself by utilizing materials and processes that are green, clean, and sustainable. Biopolymers, bio‐sourced raw materials and light weighting of parts 3D printed with photopolymer resins each represent critical directions for the future of AM. Here, we report a series of bio‐based composite resins with soybean oil derivatives, up to 20% by weight of surface‐methacrylated micro‐crystalline cellulose (MCC) and 60% total bio‐based content for vat photopolymerization based additive manufacturing. The ultimate tensile strengths of the materials were found to increase up to 3X, the Young's moduli increased up to 10X, and the glass transition temperature increased by 11.3°C when compared to the neat resin without surface‐methacrylated MCC as a filler. Working curves and shrinkage factors were used to demonstrate how the surface‐methacrylated MCC causes changes in the dimensions of printed parts, to facilitate development of optimized print parameters based on the UV intensity of the 3D printer being used. These results will allow further development of commercial 3D printable resins with a high concentration of bio‐based fillers that print well and perform on par with conventional resins. [ABSTRACT FROM AUTHOR]

Vivid biological structures with reversible adhesive properties are widely found in nature. Although current biomimicking adhesion systems have attracted extensive attention, unmet challenges remain in terms of excellent adhesion preservation, precise structural fabrication, and good environmental compatibility. By combining advanced vat photopolymerization 3D printing technology with hydrogel materials with excellent environmental adaptability, bioinspired adhesion devices present satisfactory application prospects. Herein, a systematic overview of bioinspired hydrogel adhesion devices from the perspectives of material design, structural design, and fabrication is presented. First, the main types and application prospects of vat photopolymerization 3D printed hydrogels are introduced. Subsequently, the research progress on hydrogel‐based vat photopolymerized 3D printed bionic adhesion devices is detailed. Future developments, such as balancing unmet challenges and expected opportunities, in 3D printable multiscale bionic adhesive devices are presented. [ABSTRACT FROM AUTHOR]

Digital Light Processing (DLP) technology is a highly effective molding method for creating complex structural parts. However, the low solid content of SiC stereolithography slurry has been found to diminish the mechanical properties of the ceramic, regardless of whether it is sintered by Reactive Melt Infiltration (RMI) or Precursor Infiltration and Pyrolysis (PIP). This poses a significant challenge in improving the mechanical properties of SiC ceramics manufactured through DLP additive manufacturing. In response to this challenge, a novel method of RMI combined with infiltration is proposed in this study. The process involves the filling of the pores of the green body with pyrolytic carbon from PR or pyrolytic SiC from LHBPCS through circular infiltration, effectively increasing the content of SiC in the ceramics after reaction. Notably, the elastic modulus of RM-P2 and RM-L2 samples increased by 37.39% and 33.91%, respectively, demonstrating the potential of this method for preparing ceramics with high SiC content through stereolithography additive manufacturing. This innovative approach holds promise for overcoming the limitations previously associated with SiC ceramics produced through DLP additive manufacturing, opening up new possibilities for the development of high-performance SiC-based components. [ABSTRACT FROM AUTHOR]

The possibility of exploiting visible light to induce polymerizations is extremely appealing from a technological point of view as it improves the sustainability of the overall process. To achieve this objective, it is necessary to employ single‐ or multicomponent systems containing a photoinitiator, and in some cases, a photosensitizer in combination. Due to their long‐lived excited states and reversible redox properties, transition metal complexes are a valid choice to be applied in photoinitiating systems, often exhibiting enhanced conversions compared to purely organic compounds. This review presents an overview of the transition metal complexes exploited in photopolymerization reactions. Particular attention will be devoted to recent applications in 3D printing, highlighting the possible challenges that need to be faced to achieve highly efficient and more sustainable processes. [ABSTRACT FROM AUTHOR]

Light‐based 3D printing has received significant attention due to several advantages including high printing speed and resolution. Along with the development of new technologies, material design is key for the next generation of light‐based 3D printing. Conventional printable polymeric materials, also known as photopolymers or photoresins, often lead to thermosets–polymer networks cross‐linked by permanent covalent bonds which bring limited adaptability and restricted reprocessability. Dynamic bonds that can reversibly break and reform enable network rearrangement, thereby offering unprecedented properties to the materials such as adaptability, self‐healing, and recycling capabilities. Hence, introducing dynamic bonds into materials for light‐based 3D printing is a promising strategy to further expand and meet the diverse application scenarios of 3D printed multi‐functional materials and moreover meet more demanding sustainable and nature‐inspired design considerations (e.g., adaptability and self‐healing). Herein, an overview of recent advances in dynamic photopolymers for light‐based 3D printing, aiming to bridge these two promising research fields is presented. Importantly, the current challenges are also analyzed and perspectives for further developing dynamic photopolymers for light‐based 3D printing and their potential applications are provided. [ABSTRACT FROM AUTHOR]

The optical element is a key part of manufacturing optoelectronic systems, which can realize functions such as imaging, spectroscopy, image transmission, filtering, and more. The design and manufacture of optical elements is a key issue that restricts its development, and the traditional optical component preparation method is less capable of preparing optical elements with complex structures and multiple materials. As a mature advanced manufacturing technology, photopolymerization 3D printing technology has the advantages of high printing precision and small layer thickness, which plays an important role in the preparation of optical elements. This review paper briefly provides a concise overview of the benefits and applications of photopolymerization 3D printing technology in optical element preparation The development overview and research progress of materials used for the preparation of optical elements by photopolymerization 3D printing are discussed. Finally, it summarizes the current limitations, challenges, future development prospects, and potential applications in the realm of optical element manufacturing. [ABSTRACT FROM AUTHOR]

Photocuring 3D printing of hydrogels, with sophisticated, delicate structures and biocompatibility, attracts significant attention by researchers and possesses promising application in the fields of tissue engineering and flexible devices. After years of development, photocuring 3D printing technologies and hydrogel inks make great progress. Herein, the techniques of photocuring 3D printing of hydrogels, including direct ink writing (DIW), stereolithography (SLA), digital light processing (DLP), continuous liquid interface production (CLIP), volumetric additive manufacturing (VAM), and two photon polymerization (TPP) are reviewed. Further, the raw materials for hydrogel inks (photocurable polymers, monomers, photoinitiators, and additives) and applications in tissue engineering and flexible devices are also reviewed. At last, the current challenges and future perspectives of photocuring 3D printing of hydrogels are discussed. [ABSTRACT FROM AUTHOR]

Based on the Body Centered Tetragonal lattice structure of vat photopolymerization printed polyurethane composites, analytical relations between cell parameters and its compressive elastic modulus are deduced. Furthermore, unified numerical expressions are proposed for the unit cell, single-layer cell, and multilayered cell. Different structures are utilized for simulating calculation and the results show that the analytical solution and simulation outcome are consistent with the experimental tests. A modified genetic algorithm is proposed to optimize the lattice structure and its relative density is greatly reduced under certain stiffness conditions. It is promising to accelerate the development and production of integrated lattice products. [ABSTRACT FROM AUTHOR]

Epoxidized vegetable oils and limonene dioxide, a bis-epoxide derived from the terpene limonene, are photo-copolymerized to yield highly crosslinked networks with high conversion of all epoxide groups at ambient temperature. However, the slow polymerization of such biobased formulation polymerizes is not compatible for a use in a commercial SLA 3D printer. Adding an acrylated epoxidized vegetable oil to the bis-epoxide leads to a decrease of curing time and an increase in LDO conversion to polymer. For example, in a 60:40 wt:wt mixture of LDO and epoxidized soybean oil, the conversions of both exocyclic and endocyclic epoxide groups of LDO are ≥95%. These formulations were successfully used in SLA 3D printers, leading to generation of hard and dry complex objects using biobased formulations. [ABSTRACT FROM AUTHOR]

Photo‐controlled reversible‐deactivation radical polymerization (RDRP) has recently emerged in light‐based 3D printing at macro‐ and micro‐scales, enabling the elaboration of objects with (re‐)configurable surface properties. The authors' previous work exploits nitroxide‐mediated radical photopolymerization (NMP2) in 3D micro‐printing and subsequent surface modification, by employing analkoxyamine‐based photoresist via 3D direct laser writing (DLW). However, this photoresist suffers from its low photosensitivity to wavelengths above 760 nm, limiting its suitability for commercial 3D DLW setups. To tackle these issues, a new strategy—in situ NMP2 based on a photoresist containing acommercial photoinitiator and a photosensitive‐nitroneis proposed. This photoresist is well‐suited for wavelengths commonly used by 3D DLW systems to obtain well‐defined 3D microstructures. Importantly, the in‐situ formation of alkoxyamine during fabrication allows photo‐induced surface modification of microstructures, highlighted by precise and successive surface patterning. Thesurface modification can be conducted at 800 nm or at wavelengths up to 860 nm. Subsequently, the impact of light wavelength and intensity isinvestigated to understand surface modification. The simple preparation of this novel photoresist allows facile adaptation to digital light processing for 3D macro‐printing. This work broadens the scope of photo‐controlled RDRP in 3D printing and greatly facilitates "living" 3D micro‐ and macro‐printing. [ABSTRACT FROM AUTHOR]

The fabrication of structured zeolite adsorbents through photopolymerization‐based 3D printing which offers a solution to the limitations of conventional shaping techniques has been demonstrated but many parameters still need to be optimized. In this study, we studied the influence of zeolite compensation cations on the photopolymerization and the composite's properties. Modified zeolites (LTA 4 A and FAU 13X exchanged with K+, Li+, Sr2+, Ca2+ or Mg2+) were incorporated in PEGDA with BDMK as photoinitiator, and the formulation was cured under mild conditions (LED@405 nm, room temperature, under air). Our results indicate that the nature of zeolite compensation cations affects the colorimetric properties of polymer/zeolite composites: a better translucency parameter results in higher depth of cure. After calcination at 650 °C and complete removal of PEGDA, pure zeolitic monoliths were tested for adsorption of gas molecules of interest (carbon dioxide, dichlorobenzene and water). Structured 4 A and 13X monoliths obtained by 3D printing exhibit comparable adsorption capacity to commercial beads prepared from the same zeolites. This study enhances our understanding of the photopolymerization process involved in the production of polymer/zeolite composites. These composites are used in the fabrication of zeolitic objects through 3D printing, offering potential solutions to various environmental and dental challenges. [ABSTRACT FROM AUTHOR]

In this comprehensive review, the current state of the art and recent advances in 3D printing in dentistry are explored. This article provides an overview of the fundamental principles of 3D printing with a focus on vat photopolymerization (VP), the most commonly used technological principle in dental practice, which includes SLA, DLP, and LCD (or mSLA) technologies. The advantages, disadvantages, and shortcomings of these technologies are also discussed. This article delves into the key stages of the dental 3D printing process, from computer-aided design (CAD) to postprocessing, emphasizing the importance of postrinsing and postcuring to ensure the biocompatibility of custom-made medical devices. Legal considerations and regulatory obligations related to the production of custom medical devices through 3D printing are also addressed. This article serves as a valuable resource for dental practitioners, researchers, and health care professionals interested in applying this innovative technology in clinical practice. [ABSTRACT FROM AUTHOR]

To date, overcoming the trade-off between high solid loading and print accuracy and strength, achieving high-performance and fine ZrO 2 micro-ceramic components through vat photopolymerization 3D printing remains challenging. In this study, the effects of dispersant, particle size and solid content on the dispersion, rheological behavior and stability of ZrO 2 ceramic slurry were systematically studied, and complex, fine and high-performance ZrO 2 micro-ceramic gears were successfully prepared. Then, the microstructure, mechanical properties, tribological properties and surface quality were evaluated. The results show that the rheological behavior of the slurry is the best when the optimal dispersant content is 3.5 wt%. With the increase of solid content, the sintering shrinkage of ZrO 2 (3Y)/Al 2 O 3 ceramics decreased, while the relative density, compressive strength, flexural strength, fracture toughness and hardness increased. The prepared micro-ceramic gears not only have fine structure, but also have dense microstructure and good mechanical properties. The relative density, compressive strength, flexural strength, fracture toughness and hardness strength of ZrO 2 (3Y)/Al 2 O 3 ceramics can reach 98.53 %, 1900 MPa, 648 MPa, 6.4 MPa × m1/2 and 13.40 GPa, respectively. In particular, this study couples the printing accuracy and strength with the solid load. By adjusting the relationship between the fixed load and the shrinkage rate, the printing of samples with different sizes is realized, which breaks through the accuracy limit of the printing equipment and provides a new idea for the preparation of micro-ceramic gears. [ABSTRACT FROM AUTHOR]

In this work, we developed and analyzed a biphasic calcium phosphate (BCP) bioceramic for bone regeneration using stereolithography (SLA). The SLA method is a promising additive manufacturing (AM) technique capable of creating BCp parts with high accuracy and efficiency. However, the ceramic suspension used in SLA exhibits significantly higher viscosity and is not environmentally friendly. Therefore, adequate preparation of a suspension with low viscosity and high solid loading is essential. In this paper, we optimized the effects of surfactant doses and solid loading on the BCp slurry, and initially examined the process parameters of photocuring, debinding, and sintering. The utilization of 9 wt % Disperbyk (BYK) with a 40 vol % loading of BCp bioceramics exhibited a reasonably low viscosity of 8.9 mPa·s at a shear level of 46.5 s−1. Functional and structural analyses confirmed that BCp was retained after photocuring and subsequent treatment, which were incorporated into the BYK dispersion. The 3D printed objects with different sintered temperatures, specifically at 1100 °C, 1200 °C, and 1300 °C, were further optimized. Additionally, the surface roughness, porosity, and mechanical properties of BCp green parts were systematically investigated. Most importantly, in vitro analysis of cell attachment, differentiation, and red alizarin analysis could support the application of bone regeneration.

The process of additive manufacturing (AM), commonly known as 3D printing, is a method of constructing a component by progressively adding material in layers using digital 3D design information. As part of 'Industry 4.0,' many industrial technologies are rapidly increasing to thrive in the twenty-first century. This study goes over seven different types of additive manufacturing in great detail. These technologies make it possible to make complex, high-value parts quickly and in small quantities without using as much energy or material or making as many tools as subtractive manufacturing does. Besides, AM also possesses some particular challenges, like post-processing, material unavailability, software issues, etc. The application of AM is expanding rapidly from micro to macro-scale sectors. 3D printing technology will change industrial operations in the following years. Eventually, the elected technology will be closely related to the proposed function.

Functional inks for light‐based 3D printing are actively being searched for being able to exploit all the potentialities of additive manufacturing. Herein, a fast visible‐light photopolymerization process is showed of conductive PEDOT:PSS hydrogels. For this purpose, a new Type II photoinitiator system (PIS) based on riboflavin (Rf), triethanolamine (TEA), and poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is investigated for the visible light photopolymerization of acrylic monomers. PEDOT:PSS has a dual role by accelerating the photoinitiation process and providing conductivity to the obtained hydrogels. Using this PIS, full monomer conversion is achieved in less than 2 min using visible light. First, the PIS mechanism is studied, proposing that electron transfer between the triplet excited state of the dye (3Rf*) and the amine (TEA) is catalyzed by PEDOT:PSS. Second, a series of poly(2‐hydroxyethyl acrylate)/PEDOT:PSS hydrogels with different compositions are obtained by photopolymerization. The presence of PEDOT:PSS negatively influences the swelling properties of hydrogels, but significantly increases its mechanical modulus and electrical properties. The new PIS is also tested for 3D printing in a commercially available Digital Light Processing (DLP) 3D printer (405 nm wavelength), obtaining high resolution and 500 µm hole size conductive scaffolds. [ABSTRACT FROM AUTHOR]

Two-photon lithography (TPL) is a laser-based additive manufacturing technique that enables the printing of arbitrarily complex cm-scale polymeric 3D structures with sub-micron features. Although various approaches have been investigated to enable the printing of fine features in TPL, it is still challenging to achieve rapid sub-100 nm 3D printing. A key limitation is that the physical phenomena that govern the theoretical and practical limits of the minimum feature size are not well known. Here, we investigate these limits in the projection TPL (P-PTL) process, which is a high-throughput variant of TPL, wherein entire 2D layers are printed at once. We quantify the effects of the projected feature size, optical power, exposure time, and photoinitiator concentration on the printed feature size through finite element modeling of photopolymerization. Simulations are performed rapidly over a vast parameter set exceeding 10,000 combinations through a dynamic programming scheme, which is implemented on high-performance computing resources. We demonstrate that there is no physics-based limit to the minimum feature sizes achievable with a precise and well-calibrated P-TPL system, despite the discrete nature of illumination. However, the practically achievable minimum feature size is limited by the increased sensitivity of the degree of polymer conversion to the processing parameters in the sub-100 nm regime. The insights generated here can serve as a roadmap towards fast, precise, and predictable sub-100 nm 3D printing. [ABSTRACT FROM AUTHOR]

Vat photopolymerisation (VP) three-dimensional printing (3DP) has attracted great attention in many different fields, such as electronics, pharmaceuticals, biomedical devices and tissue engineering. Due to the low availability of biocompatible photocurable resins, its application in the healthcare sector is still limited. In this work, we formulate photocurable resins based on urethane dimethacrylate (UDMA) combined with three different difunctional methacrylic diluents named ethylene glycol dimethacrylate (EGDMA), di(ethylene glycol) dimethacrylate (DEGDMA) or tri(ethylene glycol) dimethacrylate (TEGDMA). The resins were tested for viscosity, thermal behaviour and printability. After printing, the 3D printed specimens were measured with a digital calliper in order to investigate their accuracy to the digital model and tested with FT-IR, TGA and DSC. Their mechanical properties, contact angle, water sorption and biocompatibility were also evaluated. The photopolymerizable formulations investigated in this work achieved promising properties so as to be suitable for tissue engineering and other biomedical applications. [ABSTRACT FROM AUTHOR]

The process of additive manufacturing (AM), commonly known as 3D printing, is a method of constructing a component by progressively adding material in layers using digital 3D design information. As part of 'Industry 4.0,' many industrial technologies are rapidly increasing to thrive in the twenty-first century. This study goes over seven different types of additive manufacturing in great detail. These technologies make it possible to make complex, high-value parts quickly and in small quantities without using as much energy or material or making as many tools as subtractive manufacturing does. Besides, AM also possesses some particular challenges, like post-processing, material unavailability, software issues, etc. The application of AM is expanding rapidly from micro to macro-scale sectors. 3D printing technology will change industrial operations in the following years. Eventually, the elected technology will be closely related to the proposed function. [ABSTRACT FROM AUTHOR]

Along with the rapid and extensive advancements in the 3D printing field, a diverse range of uses for 3D printing have appeared in the spectrum of medical applications. Vat photopolymerization (VPP) stands out as one of the most extensively researched methods of 3D printing, with its main advantages being a high printing speed and the ability to produce high-resolution structures. A major challenge in using VPP 3D-printed materials in medicine is the general incompatibility of standard VPP resin mixtures with the requirements of biocompatibility and biofunctionality. Instead of developing completely new materials, an alternate approach to solving this problem involves adapting existing biomaterials. These materials are incompatible with VPP 3D printing in their pure form but can be adapted to the VPP chemistry and general process through the use of innovative mixtures and the addition of specific pre- and post-printing steps. This review's primary objective is to highlight biofunctional and biocompatible materials that have been adapted to VPP. We present and compare the suitability of these adapted materials to different medical applications and propose other biomaterials that could be further adapted to the VPP 3D printing process in order to fulfill patient-specific medical requirements. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV)-curing technology as a photopolymerization technology has received widespread attention due to its advantages of high efficiency, wide adaptability, and environmental friendliness. Ultraviolet-based 3D printing technology has been widely used in the printing of thermosetting materials, but the permanent covalent cross-linked networks of thermosetting materials which are used in this method make it hard to recover the damage caused by the printing process through reprocessing, which reduces the service life of the material. Therefore, introducing dynamic bonds into UV-curable polymer materials might be a brilliant choice which can enable the material to conduct self-healing, and thus meet the needs of practical applications. The present review first introduces photosensitive resins utilizing dynamic bonds, followed by a summary of various types of dynamic bonds approaches. We also analyze the advantages/disadvantages of diverse UV-curable self-healing polymers with different polymeric structures, and outline future development trends in this field. [ABSTRACT FROM AUTHOR]

Vat photopolymerization relies on the light‐induced polymerization of liquid photopolymer to produce the targeted structure. Among all the polymers prepared by vat photopolymerization, due to their numerous properties polyurethanes have recently gained great attention in the industrial and academic fields. In this review article, recent progress in printing techniques, resin compositions, and applications related to 3D/4D printing by vat photopolymerization of polyurethanes are highlighted. [ABSTRACT FROM AUTHOR]

Purifications of biologics can be improved using 3D printed stationary phases with perfectly ordered morphology. However, limited spatial resolution and lack of porous materials have hindered application of additive manufacturing in bioprocessing. To bridge this gap, digital light processing and polymerization‐induced phase separation are combined to fabricate platform materials with bed morphology at the micrometer scale, and porous network in the nanometer scale. Four different porous inks are developed, 3D printed, and characterized in terms of their rheological behaviour, polymerization kinetics, and printing resolution. Rapid 3D printing (down to 1 h) is achieved at scale (up to 100 mL column) of porous supports (50% porosity) at high resolution (up to 50 µm for linear features and 200 µm for complex geometries). 3D‐printed gyroids are chemically functionalized with various ion exchange ligands. These are successfully challenged for i) the separation of model proteins in dynamic conditions and ii) protein capture from a clarified cell harvest, demonstrating dynamic binding capacities between 5 and 16 mg mL−1 and up to 86% purity in a single run. This work introduces a rapid and facile approach to 3D printing porous inks to fabricate perfectly ordered stationary phases for downstream processing. [ABSTRACT FROM AUTHOR]

3D printing is an attractive method to accurately construct artificial organs or alternative materials with complicated structures and functional performance. Naturally derived hydrogels have emerged as promising materials for the preparation of biomimetic 3D organization or scaffolds by 3D printing due to their good biocompatibility, high water content, and fascinating 3D network. However, the poor printing properties and weak structural stability of naturally derived hydrogels limit their applications. In this study, photopolymerizable hydrogels are designed based on maleic chitosan (MCS) and thiolated sodium hyaluronate (SHHA). The Michael addition between MCS and SHHA improves the viscosity of the mixed solution. Moreover, it benefits the 3D printing process, followed by photopolymerization (acrylate‐thiol step‐chain polymerization and acrylate–acrylate chain polymerization) to form a stable covalent network rapidly. The rheological property, swelling behaviors, microstructure, and in vitro degradation are tuned by adjusting the molar ratio of the thiol group and acrylate group. In addition, MCS/SHHA hydrogel scaffolds with good accuracy and enhanced structural stability are prepared using extrusion‐based 3D printing and photopolymerization technology. The hydrogels display excellent cytocompatibility and can support adherence of L929 cells, which can be used as prospective materials for tissue engineering applications. [ABSTRACT FROM AUTHOR]

Additive manufacturing with vat photopolymerization (VP) as an emerging manufacturing method addresses various goals for enhanced sustainability including waste reduction, dematerialization, and the customization of intricate and complex 3D parts. Unsaturated polyesters (UPEs) recently gained attention as a sustainable material source for lithographic additive manufacturing. While previous methods demonstrated the printability of UPE-based resins, these studies lack the solvent-free approach demonstrated herein. Furthermore, the effective depolymerization of polyester thermosets has remained relatively unexplored. This report demonstrates structure–property relationships and subsequent solvent-free VP of UPEs with PEGDA-575 as a reactive diluent with effective depolymerization of polyester thermosets through base-catalyzed methanolysis. [ABSTRACT FROM AUTHOR]

In order to investigate the photopolymerization properties of the alkyl chain length dependence Type I photoinitiators, in this study, a series of visible‐light‐absorbing triphenylamine oxime esters (Peko‐A‐D, and reference TP‐1M) containing various alkyl chain length in the periphery were synthesized. That is, an alkane segment contains isopropyl for Peko‐A, butyl for Peko‐B, undecane for Peko‐C, pentadecane for Peko‐D and methyl for TP‐1M, respectively. Except for Peko‐D, all of them have good organo‐solubility and can dissolve in testing monomer (trimethylolpropane triacrylate, TMPTA). All the oxime esters give from near UV to visible‐light absorption regions with maximum absorption peaks at around 360 nm and show rather red‐shifted compared to the commercial OXE‐01 compound. Accordingly, the photochemical reaction behavior was studied by cyclic voltammograms (CV), electron spin resonance (ESR) and steady‐state photolysis. In addition, the oxime esters based photoinitiating systems are studied through photo‐DSC experiment based on various light exposure wavelengths (UV lamp, LED@365 nm and LED@405 nm). Under different light source, the penetration affects the final double conversion efficiencies. As a result, all the oxime esters‐based formulation shows better double conversion efficiencies upon LED@405 nm as an irradiation source. Finally, the new oxime ester photoinitiating system was capable applied in direct laser write to generate 3D patterns using a laser diode @405 nm. [ABSTRACT FROM AUTHOR]

Vat photopolymerization typically prints highly crosslinked networks. Printing hydrogels, which are also networks but with a high swelling capacity in water and therefore with low crosslinking density, is a challenge for this technique. However, it may be of interest in medicine and in other areas, since it would allow for the preparation of this type of 3D-shaped material. In this work, an approach for printing hydrogels via vat photopolymerization that uses a mixture of stable and hydrolysable crosslinkers has been evaluated so that an initial highly crosslinked network can be printed, although after hydrolysis it becomes a network with low crosslinking. This approach has been studied with PEO/PEG-related formulations, that is, with a PEG-dimethacrylate as a stable crosslinker, a PEO-related derivative carrying β-aminoesters as a degradable crosslinker, and PEG-methyl ether acrylate and hydroxyethyl acrylate as monofunctional monomers. A wide family of formulations has been studied, maintaining the weight percentage of the crosslinkers at 15%. Resins have been studied in terms of viscosity, and the printing process has been evaluated through the generation of Jacobs working curves. It has been shown that this approach allows for the printing of pieces of different shapes and sizes via vat photopolymerization, and that these pieces can re-ajust their water content in a tailored fashion through treatments in different media (PBS or pH 10 buffer). [ABSTRACT FROM AUTHOR]

Abstract Photoinitiating systems (PISs) are key components in photocurable formulations (inks) for three-dimensional (3D) printing. Natural PISs are promising and more environmentally friendly alternatives to conventional photoinitiators. These systems offer enhanced features such as less toxicity and therefore, higher biocompatibility. Furthermore, they can be found in a large “color palette” variety (absorbing in the different regions of the UV-visible spectrum) enabling new possibilities in the field of 3D printing. In this review, we outline the current efforts to implement natural and naturally derived PISs in light-based 3D printing. First, recently applied natural PISs and their performance for light-based 3D printing are discussed. In a second part, an overview of naturally derived PISs including the most common synthetic strategies are provided. Last, current challenges as well as future perspectives of the field are discussed. Introduction Natural Photoinitiating Systems Naturally Derived Photoinitiating Systems Conclusions and Outlook

Abstract 3D printing is an attractive method to accurately construct artificial organs or alternative materials with complicated structures and functional performance. Naturally derived hydrogels have emerged as promising materials for the preparation of biomimetic 3D organization or scaffolds by 3D printing due to their good biocompatibility, high water content, and fascinating 3D network. However, the poor printing properties and weak structural stability of naturally derived hydrogels limit their applications. In this study, photopolymerizable hydrogels are designed based on maleic chitosan (MCS) and thiolated sodium hyaluronate (SHHA). The Michael addition between MCS and SHHA improves the viscosity of the mixed solution. Moreover, it benefits the 3D printing process, followed by photopolymerization (acrylate‐thiol step‐chain polymerization and acrylate–acrylate chain polymerization) to form a stable covalent network rapidly. The rheological property, swelling behaviors, microstructure, and in vitro degradation are tuned by adjusting the molar ratio of the thiol group and acrylate group. In addition, MCS/SHHA hydrogel scaffolds with good accuracy and enhanced structural stability are prepared using extrusion‐based 3D printing and photopolymerization technology. The hydrogels display excellent cytocompatibility and can support adherence of L929 cells, which can be used as prospective materials for tissue engineering applications.

Vat polymerization is a type of additive manufacturing that is used extensively to produce micro‐architected structures for mechanical applications, which brings the mechanical properties of photopolymerized resins into sharp focus. However, it is known that photopolymerization is sensitive to a number of factors, perhaps the most notorious of which is oxygen inhibition. Herein, the degree to which oxygen inhibition influences the macroscopic and microscopic properties of structures made using vat polymerization is explored. This work is motivated by an observation of lattices being >4 times softer in the experiment than predicted by simulation, which is hypothesized to be due to the material at the surface being incompletely cured. This hypothesis is supported by four‐point bending tests in which flexural modulus is found to increase with beam thickness. Nanoindentation and bulk compression studies show that this surface softening is present for three distinct resins. Importantly, it is observed that structures post‐print cured in nitrogen are stiffer than those post‐print cured in air, however, regardless of the post‐print curing environment, printing samples in the presence of oxygen makes them softer than samples photocured in nitrogen. Collectively, these results show the outsized influence of oxygen inhibition on micro‐architected structures realized using vat polymerization. [ABSTRACT FROM AUTHOR]