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Multifractal properties of acrylated epoxidized soybean oil with and without a photoinitiator have been investigated. Using multifractal detrended fluctuation analysis, the photopolymerization process is analyzed by varying illumination duration and intensity. The research is conducted in two stages: the results concerning temperature fluctuations of the entire photoirradiation process are initially presented followed by a sliding window procedure to monitor system complexity during light cycling. Various multifractal measures including the generalized Hurst exponent h(q), the multifractal Rényi exponent τ(q), the generalized fractal dimensions D(q) with the left and right side curvature (ΔDL, ΔDR), the multifractal singularity exponents α, the multifractal spectrum f (α), and the multifractal heat capacity C(q) with its integrated characteristic Carea are examined for both initial and shuffled series. The empirical results demonstrate that the moments of switching on and switching off photoirradiation are characterized by an instantaneous increase in the degree of multifractality of the system. It is hypothesized that the observed increase in multifractality at the light-switching-on/off stages is indicative of a quasi-phase transition, which may be associated with the transformation of orientational defects in the polymer network. [ABSTRACT FROM AUTHOR]

The greater transparency of the polymer obtained by adding a small amount of molecular iodine to the liquid photopolymerizing composition is satisfactorily explained by the formation of a π,σ-type charge transfer (CT) complex of oligocarbonate dimethacrylate with molecular iodine. The CT band at 360 nm absorbs a significant part of the actinic radiation such that the rate of the photolytic decomposition of the photoinitiator in the initial polymerization stage permits release of free volume from the polymer into the liquid part of the photopolymerizing composite. Layer-by-layer photopolymerization occurs at advanced stages due to the thin upper layers exposed to UV irradiation becoming steadily more transparent. [ABSTRACT FROM AUTHOR]

UV-activated catalytic hydrosilation is a low-temperature crosslinking process that has attracted attention for its high efficiency and lower energy demand relative to thermal curing. In this study, formulations comprising industrially relevant model silanes and Pt photocatalysts trimethyl(methylcyclopentadienyl)platinum(IV) and trimethyl(pentamethylcyclopentadienyl)platinum(IV) (MeCpPtMe3 and Cp*PtMe3, respectively) were prepared with and without a photosensitizer (PS) and assessed for catalytic performance by a novel strategy. Photopolymerizations were initiated using different wavelengths from LEDs and monitored in real-time using an Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) "well" strategy to track the degree of cure in ultra-thin films by consumption of hydride via the disappearance of the Si-H bending absorption band at 915 cm−1. Irradiation of formulations with 365 nm excitation showed higher conversions relative to 400 nm light and improvements to calculated initial reaction rates by incorporation of a PS suggested increased sensitization to 365 nm irradiation. To the best of our knowledge, this is the first study to report catalytic performance, electronic absorption spectroscopic data, and the crystal structure of Cp*PtMe3. [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]

Porosity-related characteristics of biomedical three-dimensional (3D) scaffolds govern mass transport properties which, in turn, dictate the success of implants in vivo. The accurate determination of permeability and microstructural properties in highly-porous materials – like implantable bone scaffolds – still represents a challenge due to the complex architecture of struts and voids in 3D. In the present study, the complete set of mass transport properties of bioactive glass scaffolds produced by vat photopolymerization was reliably determined by combining experimental assessment, advanced imaging and mathematical modelling based on the Ergun-Wu approach. Specifically, the intrinsic permeability of the scaffolds was experimentally estimated by acoustic measurements, and the pore diameter was calculated through implementing an innovative fractal model. An accurate statistical analysis of the results provided evidence of the robustness of the overall strategy, which can be potentially extended and adapted to the analysis of other types of sintered porous (bio)materials. [ABSTRACT FROM AUTHOR]

Vat photopolymerization (VPP) has made significant achievements in the fabrication of BaTiO 3 ceramics. However, the piezoelectric performance of pure BaTiO 3 ceramics fabricated by VPP technology is poor. In this work, the piezoelectric properties of printed BaTiO 3 ceramic were significantly improved by using the strategies of material modification. BaTiO 3 -xBaSnO 3 (BT-xBS) green bodies with high quality were obtained under the conditions of a photoinitiator content of 2 wt% and an exposure energy of 100 mJ/cm2. The Curie peak of BT-xBS samples gradually moved to low temperature and the peak gradually widened. Piezoelectric constant (d 33) showed a trend of first increasing and then decreasing, and the maximum value appeared in BT-6BS samples. BT-6BS samples exhibited the excellent piezoelectric performance with piezoelectric constant (d 33), piezoelectric voltage constant (g 33) and transduction coefficient (d 33 × g 33) reaching 283 pC/N, 15.02 × 10−3 Vm/N and 4.25 × 10−12 m2/N, respectively, which are 57%, 14% and 79% higher than those of printed pure BaTiO 3 ceramics. [ABSTRACT FROM AUTHOR]

The effects of salt water exposure at deep ocean depth pressures when coupled with low temperatures on the material characteristics of three unique additively manufactured polymers has been investigated through a detailed experimental approach. The polymers in the study were manufactured utilizing both Vat Photopolymerization and Material Extrusion printing techniques. The Material Extrusion process was utilized to produce material specimens of Stratasys ULTEM 9085 and Markforged Onyx while the Vat Photopolymerization process was used to produce specimens of Accura ClearVue. The ULTEM 9085 and Markforged Onyx are filament based polymers and the ClearVue is a liquid based resin. The specimens were first submerged in a high pressure, salt water bath of 3.5% NaCl solution at 34.5 MPa (5000 lb/in²) for a total exposure time of 60 days to determine the water absorption characteristics. Subsequent to the salt water exposure at high pressure, the specimens were evaluated to determine changes in tension, compression, flexure, and in-plane fracture properties. To determine the effects of water saturation and low temperature coupling, the mechanical testing was performed at temperatures of 20 °C, 0 °C and -20 °C in both dry and saturated conditions. Additionally, non-destructive testing in the form of TeraHertz and FIRT imaging was conducted to analyze the physical material changes through the thickness of the material due to the saline water absorption. To quantify the change in material storage and loss moduli properties, Dynamic Mechanical Analysis (DMA) characterization was performed on each of the AM polymers in dry and saturated states. The DMA testing also quantified changes in the Glass Transition Temperature because of salt water exposure. In summary, The current study investigates the effects of coupled long term/high pressure salt water exposure with low temperatures on the mechanical and material characteristics of three unique AM polymers by: (1) immersing the materials in a salt water solution at 34.5 MPa for 60 days, (2) Conducting post exposure mechanical testing on the materials at 0 °C and -20 °C with comparisons to 20 °C testing on dry specimens, and quantifies changes in material properties through DMA experiments. The results from all testing in the study show that high pressure salt water exposure when coupled with low temperatures has unique effects on each of the materials considered in the study and careful consideration to each parameter must be given based on the material type when components will be employed in marine operations. [ABSTRACT FROM AUTHOR]

Additive manufacturing (3D printing) technologies, especially vat photopolymerization (VPP), provide a cost-effective and efficient approach for the fabrication of heat dissipation devices with complex geometric designs. The incorporation of inorganic thermal conductive fillers into resin matrix is widely recognized as an effective way to enhance thermal conductivity. Notably, the synergistic effect of hybrid fillers can further enhance thermal conductivity. However, the consequent drastic increase in viscosity of the UV-curable resin may decrease the success rate and accuracy of printing on commercial VPP 3D printers. In this work, hexagonal boron nitride (h-BN) platelets and spherical h-BN together with β-Si 3 N 4 are introduced into the UV-curable resin system. Corresponding results proved that h-BN together with β-Si 3 N 4 provide a synergistic effect on the thermal conductivity enhancement compared to the filler in single morphology only. Moreover, owing to the spherical structure, low-viscosity UV-curable resin with high solid content can be prepared. In specific, a thermal conductive polymer composite material with a solid content of 60 wt% is prepared, which exhibits high thermal conductivity (1.42 W/mK), representing an enhancement of up to 610 % compared to neat resin. In subsequent application demonstrations, 3D printed heat dissipation devices with as-prepared resin composite material have been shown to effectively enhance the heat dissipation rate for the heating device. [ABSTRACT FROM AUTHOR]

Employed ubiquitously in oral restorations, zirconia-based bioceramics face challenges with low-temperature degradation (LTD) in the tetragonal phase (t-ZrO 2) within oral environments. In order to improve the resistance of ZrO 2 ceramics to LTD, this study utilized vat photopolymerization technology to prepare 7Ce3Y–ZrO 2 (7 mol% CeO 2 and 3 mol% Y 2 O 3). By adjusting the dispersant content and photosensitive resin ratio enabled the attainment of a 63.5 μm curing depth with a 400 mJ/cm2 exposure, meeting the requirements for vat photopolymerization printing. After sintering at 1550 °C, these ceramics shown a relative density of 97.84 % and an impressive flexural strength of 503.1 MPa. Accelerated LTD tests were conducted to assess LTD-resistance, revealing no degradation in mechanical properties or evidence of tetragonal to monoclinic phase transitions. This stability is credited to the cerium ions' efficacy in hindering oxygen vacancy formation and subsequent aging within the ZrO 2. This study affirms that CeO 2 –Y 2 O 3 co-stabilized ZrO 2 ceramics prepared using vat photopolymerization technology exhibit outstanding properties and resistance to LTD, showcasing significant potential in the field of oral restoration. [ABSTRACT FROM AUTHOR]

In the field of wound healing treatment, the development of new materials is essential to cover multiple functions, such as acceleration of the healing process, prevention of infection and response to stimuli, especially if they present lower costs or are easier to manufacture. These properties are of great importance to prompt skin cicatrization. In this work, new multifunctional skin dressings for wound healing and infection prevention are developed based on new hydrogel materials. The dressings are produced via a straightforward and environmentally friendly one‐pot photopolymerization manufacturing process utilizing vitamin B2 aqueous solutions as sensitizer, and energy‐efficient blue light sources. These dressings exhibit a high swelling capacity, pH and temperature responsiveness, biocompatibility, antimicrobial activity in the absence of conventional antibiotics, and are capable of promoting wound healing. The formulation is based on the combination of three monomers: 2‐((methacryloyloxy)ethyl)trimethylammonium chloride, methacrylic acid and N‐vinyl caprolactam. Collagen, hyaluronic acid, and essential oil of hop are added to enhance antimicrobial properties and stimulate regenerative cellular processes. In vivo experiments have demonstrated that pristine dressings are superior in promoting collagen and fibroblast regeneration and accelerating cicatrization as compared to dressings containing natural products. The dressing embedded with hop also displayed antimicrobial characteristics. The preparation and testing of these new efficient wound dressings are described. This study is distinctive in its integration of environmentally conscious manufacturing techniques with innovative material formulations, resulting in superior wound dressings that are both cost‐effective and highly functional. By achieving enhanced healing and infection prevention without the employment of conventional antibiotics, this work represents a substantial advancement in sustainable and effective wound care management. [ABSTRACT FROM AUTHOR]

Radiation curing is an excellent option for the economical implementation of coatings while simultaneously producing technically advanced products. Nevertheless, the number of materials used is mainly limited to pure (meth)acrylate and epoxy systems. Polyisocyanurates could be an excellent addition to this range, especially due to their thermal and chemical stability. In this work, through the use of a transition metal‐based photocatalyst, as well as the use of 1,5‐diazabicyclo(4.3.0)non‐5‐en as a co‐catalyst, formulations are presented, which enable pure polyisocyanurates to be used in radiation‐based coating technology. Trimerization with this system using any primary isocyanates worked and consequently thus opened the possibility for aromatic and aliphatic polyisocyanurates. Using monofunctional isocyanates, the theoretical background of trimerization as well as the theoretical enthalpy is evaluated and the possibilities as well as the limitations for poly‐trimerization of polyisocyanurates are analyzed. Finally, photo‐induced catalytic poly‐trimerization of aliphatic isocyanates is used to obtain samples with a Tg in the range of 100 °C and onset of degradation above 400 °C. Thus, for the first time, a framework for the use of isocyanates in the field of photopolymerization and, in particular, in the field of radiation‐based coating of polyisocyanurates is provided for further development. [ABSTRACT FROM AUTHOR]

We report on concomitant photoinitiated polymerization‐induced macrophase and microphase separation strategies to produce hierarchically structured recyclable poly(n‐butyl acrylate) based elastomeric materials. The investigated crosslinker‐free formulations are composed of n‐butyl acrylate monomer and a UV photo‐initiator mixed with poly(methyl methacrylate)‐b‐poly(n‐butyl acrylate)‐poly(methyl methacrylate) ABA triblock copolymers. Two different pre‐synthesized copolymers are used to control the macrophase separation. One synthesized by nitroxide‐mediated radical polymerization (NMRP), and a second by anionic polymerization (AP). Essentially, NMRP route leads to copolymer with unsaturated chain ends, activated during UV photopolymerization. On the other hand, the copolymer synthesized by AP are chemically inert. That dissimilarity is also highlighted by time‐resolved FTIR and SAXS, performed to monitor respectively monomer conversion and nanostructure evolution during photopolymerization. The experimental data demonstrate that the reactivity of the triblock copolymer impacts drastically the polymerization kinetics and the self‐assembly processes. Finally, the rheological analysis shows that the produced materials present a solid‐like behavior at low frequencies despite a large PnBA content (i.e., 85 wt%). This property is associated to the phase segregation and to the sample hierarchical morphology. [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate the effect of ethanol on the properties of acrylic-urethane resin products obtained by vat photopolymerization using the masked stereolithography method. The effect of alcohol at concentrations of 15, 25, and 35% in the resin on the chemical structure, weight, thickness of the samples, and mechanical properties in static tabltensile tests performed immediately after printing and one month later were studied. The results obtained were evaluated in terms of the use of ethanol as a cosolvent to help load the resin with agomelatine for the potential of obtaining microneedle transdermal systems. It was shown that in terms of stability of properties, the most favorable system was resin with the addition of alcohol at a concentration of 15%. The greatest changes induced by the presence of the solvent in the resin were observed in the case of tensile properties, where the alcohol caused a decrease in the plasticity of the material, reducing the relative elongation at break from 14% for the pure resin to 4% when the alcohol concentration was 35%. Young's modulus and tensile strength also decreased with the addition of alcohol by 18% and 31%, respectively, for testable samples with the maximum amount of alcohol in the resin. The deterioration in properties is most likely related to the effect of the solvent on the radical polymerization process of the resin, particularly the phenomenon of chain transfer to the solvent, which is important in view of the intended application of the developed material. [ABSTRACT FROM AUTHOR]

Benzophenone and its derivatives are widely used as UV filters and UV‐ink photoinitiators. The photoinitiating properties of benzophenones depend on their degree of conjugation and delocalization within the molecule. By understanding how conjugation, delocalization, and different substituents affect these properties, benzophenone derivatives can be customized for specific applications. Using quantum mechanical calculations based on B3LYP/6‐311++G(d, p) density functional theory (DFT), chemical reactivity, stability, and photoinitiating capabilities of 4‐(4‐methylphenylthio)benzophenone are analyzed. This includes studying its physical and chemical properties in the gas phase, as well as its excited state electronic transitions, vibrational characteristics, and spectroscopic properties both in gas phase and in various solvents. The DFT‐computed infrared spectra match experimental results. The UV/Visible spectra shows absorption towards longer wavelengths due to extended delocalization of π‐electrons. In different solvents with varying polarity, the absorption spectra exhibit high‐intensity peaks, shift in excitation energy and wavelengths based on the polarity of the solvent. This knowledge allows for the development of novel initiators with customized light absorption, excited state lifetimes, and reaction selectivities, which can enhance processes like UV‐curing, photopolymerization, and other light‐driven reactions. [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]

Alumina (Al2O3) ceramics are widely used in electronics, machinery, healthcare, and other fields due to their excellent hardness and high temperature stability. However, their high brittleness limits further applications, such as artificial ceramic implants and highly flexible protective gear. To address the limitations of single-phase toughening in Al2O3 ceramics, some researchers have introduced a second phase to enhance these ceramics. However, introducing a single phase still limits the range of performance improvement. Therefore, this study explores the printing of Al2O3 ceramics by adding two different phases. Additionally, a new gradient printing technique is proposed to overcome the limitations of single material homogeneity, such as uniform performance and the presence of large residual stresses. Unlike traditional vat photopolymerization printing technology, this study stands out by generating green bodies with varying second-phase particle ratios across different layers. This study investigated the effects of different contents of sepiolite fiber (SF) and 316L stainless steel (SS) on various aspects of microstructure, phase composition, physical properties, and mechanical properties of gradient-printed Al2O3. The experimental results demonstrate that compared to Al2O3 parts without added SF and 316L SS, the inclusion of these materials can significantly reduce porosity and water absorption, resulting in a denser structure. In addition, the substantial improvements, with an increase of 394.4% in flexural strength and an increase of 316.7% in toughness, of the Al2O3 components enhanced by incorporating SF and 316L SS have been obtained. [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]

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]

Nowadays, photopolymerization has spanned across all academic and industrial applications due to its appealing features such as energy saving, environmentally‐friendly polymerization conditions, high monomer conversions, rapid polymerization kinetics and so on. Photoinitiator (PI), as a crucial component of the photoinitiating system (PIS) are capable of interacting with light efficiently, enabling to generate initiating species in mono or multicomponent systems. In this work, 13 phenothiazine‐based oxime esters (OXEs) (never reported before) were synthesized and their photoinitiation abilities for the free radical photopolymerization (FRP) of acrylates were examined upon irradiation with LED@405 nm. Parallel to their photochemical reactivities, their abilities to initiate thermal polymerization processes were also investigated. Finally, these OXEs exhibited excellent photo/thermal initiation performances, demonstrating their dual initiation properties. Phenothiazine‐based oxime esters can be used as PIs in 3D printing as well as thermal initiator in the manufacturing of carbon fiber composites. [ABSTRACT FROM AUTHOR]

Stimuli‐responsive materials have recently gained significant attention in the field of soft robotics, sensors, and biomimetic devices. The most facile way for the fabrication of such materials remains to endow bilayer structures which are fabricated with the combination of active and passive layers. Although, easily fabricated, these structures suffer from the generation of stress points between connection areas. In this work we develop a method to create a thin film with controlled cross‐link variation across its thickness. The cross‐link gradient is achieved through polymerization induced diffusion of dithiol molecules in thiol‐ene network. As a result, the film exhibits bending deformation upon illumination with light or exposure to a chemical solvent, thereby demonstrating dual responsiveness. Light actuation of the film is achieved via photothermal effects due to the incorporation of dye into the system which can absorb UV light and heat the network. While solvent induced actuation is due to anisotropic swelling. Furthermore, the straightforward fabrication procedure allows for the creation of more complex deformations by patterning the film using a photomask during photopolymerization. [ABSTRACT FROM AUTHOR]

4D printing has emerged as a powerful strategy capable of revolutionizing additive manufacturing by enabling objects to dynamically transform overtime on demand. Despite significant progress, the full potential remains unrealized, particularly in the utilization of dynamic covalent chemistry. This study introduces a new approach using a multifunctional cross‐linker with alkoxyamine functionalities for 4D printing. Digital light processing (DLP) is employed for high‐resolution printing of complex objects. Leveraging alkoxyamine bonds' dynamic and living characteristics, the printed structures can be further modified through nitroxide‐mediated polymerization (NMP) using styrene and nitroxide exchange reactions (NER). The resulting "living" printed structures exhibit the unique ability to undergo both "growth" and "degrowth", dynamically adapting their size as well as the reduced Young's Modulus across a wide range (770 kPa–1.2 GPa). The chain extension by NMP and softening by NER are carefully characterized by IR and EPR spectroscopy. The presented approach opens avenues for the development of 4D printed structures with complex adaptive systems, showcasing enormous potential in a wide range of fields. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) of copper through laser‐based processes poses challenges, primarily attributed to the high thermal conductivity and low laser absorptivity of copper powder or wire as the feedstock. Although the use of copper salts in vat photopolymerization‐based AM techniques has garnered recent attention, achieving micro‐architected copper with high conductivity and density has remained elusive. In this study, we present a facile and efficient process to create complex 3D micro‐architected copper structures with superior electrical conductivity and hardness. The process entails the formulation of an ion‐exchangeable photoresin, followed by the utilization of digital light processing (DLP) printing to sculpt 3D hydrogel scaffolds, which were transformed into Cu2+‐chelated polymer frameworks (Cu‐CPFs) with a high loading of Cu2+ ions through ion exchange, followed by debinding and sintering, results in the transformation of Cu‐CPFs into miniaturized copper architectures. This methodology represents an efficient pathway for the creation of intricate micro‐architected 3D metal structures. [ABSTRACT FROM AUTHOR]

The development of visible light‐regulated polymerizations for precision synthesis of polymers has drawn considerable attention in the past years. In this study, an ancient dye, indigo, is successfully identified as a new and efficient photoacid catalyst, which can readily promote the ring‐opening polymerization of lactones under visible light irradiation in a well‐controlled manner, affording the desired polyester products with predictable molecular weights and narrow dispersity. The enhanced acidity of indigos by excitation is crucial to the H‐bonding activation of the lactone monomers. Chain extension and block copolymer synthesis are also demonstrated with this method. [ABSTRACT FROM AUTHOR]

Photopolymerizations have garnered significant attention in polymer science due to their low polymerization temperature, high production efficiency, environmental friendliness, and spatial controllability. Despite these merits, the poor penetration and severe chemical damage from ultraviolet/visible (UV/Vis) light resources pose significant barriers to their success in conventional photopolymerizations. A recent breakthrough involving the utilization of near‐infrared (NIR) laser with long wavelength has been exploited for diverse applications. With the combination of a NIR photosensitizer (PS), NIR‐induced photopolymerizations have been successfully developed to alleviate the challenges in conventional methods. The enhancement of penetration depth and safety of NIR‐induced photopolymerizations can contribute significantly to improving the efficiency of polymerization for production of intricate structures across various scales. In this concept, the typical types of PSs and polymerization mechanisms (PMs) within the NIR‐induced photopolymerization systems have been classified in detail. Additionally, the applications of various polymers achieved by NIR‐induced photopolymerizations are summarized. Furthermore, research directions and future challenges of this field are also discussed comprehensively. [ABSTRACT FROM AUTHOR]

Vat photopolymerization (VP), as an additive manufacturing process, has experienced significant growth due to its high manufacturing precision and excellent surface quality. This method enables the fabrication of intricate shapes and structures while mitigating the machining challenges associated with non-oxide ceramics, which are known for their high hardness and brittleness. Consequently, the VP process of non-oxide ceramics has emerged as a focal point in additive manufacturing research areas. However, the absorption, refraction, and reflection of ultraviolet light by non-oxide ceramic particles can impede light penetration, leading to reduced curing thickness and posing challenges to the VP process. To enhance the efficiency and success rate of this process, researchers have explored various aspects, including the parameters of VP equipment, the composition of non-oxide VP slurries, and the surface modification of non-oxide particles. Silicon carbide and silicon nitride are examples of non-oxide ceramic particles that have been successfully employed in VP process. Nonetheless, there remains a lack of systematic induction regarding the curing mechanisms and key influencing factors of the VP process in non-oxide ceramics. This review firstly describes the curing mechanism of the non-oxide ceramic VP process, which contains the chain initiation, chain polymerization, and chain termination processes of the photosensitive resin. After that, the impact of key factors on the curing process, such as the wavelength and power of incident light, particle size, volume fraction of ceramic particles, refractive indices of photosensitive resin and ceramic particles, incident light intensity, critical light intensity, and the reactivity of photosensitive resins, are systematically discussed. Finally, this review discusses future prospects and challenges in the non-oxide ceramic VP process. Its objective is to offer valuable insights and references for further research into non-oxide ceramic VP processes. [ABSTRACT FROM AUTHOR]

In this work, photoinitiation systems based on dibenzo[a,c]phenazine sensitivity to visible light were designed for their potential application in dentistry. Modification of the structure of dibenzo[a,c]phenazine consisted of introducing electron-donating and electron-withdrawing substituents and heavy atoms into position 11. The synthesized compounds are able to absorb radiation emitted by dental lamps during photoinitiation of the polymerization process. In the presence of acrylates, dibenzo[a,c]phenazines show excellent photoinitiating abilities in systems containing an electron donor or a hydrogen-atom donor as a second component. The developed systems initiate the polymerization process comparable to a commercial photoinitiator, i.e., camphorquinone. Moreover, the performed studies showed a significant shortening of the polymerization time and a reduction in the amount of light absorber. This indicates that polymeric materials are obtained at a similar rate despite a significant reduction in the concentration of the newly developed two-component photoinitiating systems. [ABSTRACT FROM AUTHOR]

Alginate is a naturally occurring polymer derived from brown algae biomass, which has numerous applications in various fields. Chemical modification of alginate is widely used to improve alginate's physicochemical properties and provide new potential for multiple applications. In this article, we modified alginate with L-DOPA, using periodate oxidation and reductive amination, to obtain more suitable biopolymer for biocatalyst immobilization and hydrogel formation. Obtained modified alginate was used for the immobilization of laccase on cell walls. For this purpose, laccase from Streptomyces cyaneus was expressed on the surface of Saccharomyces cerevisiae EBY100 cells. The obtained cell wall laccase was immobilized within L-DOPA-alginate beads by crosslinking the L-DOPA-alginate with calcium ions and laccase. The effect of additional crosslinking of beads by green light-induced photopolymerization with eosin Y was investigated. The immobilized laccase systems were used for dye decolorization and investigated in multiple treatment processes. Beads with L-DOPA-alginate with a higher degree of modification (5.0 mol%) showed higher enzymatic activity and better decolorization efficiency than those with a lower degree of modification (2.5 mol%). Obtained immobilized biocatalysts are suitable for decolorizing dye Evans Blue due to their high efficiency and reusability. [ABSTRACT FROM AUTHOR]

This study demonstrates the use of photopolymerization to create semi-crystalline linear polymers suitable for thermally reversible materials in dental cast moldings produced from 3D printing. An aromatic diallyl, aliphatic dithiol chain extender, and monofunctional thiol were used in a photoinitiated system. The photopolymerization and crystallization kinetics as a function of chemistry and temperature were investigated using spectroscopy and calorimetry. These insights were used to realize vat photopolymerization-based 3D printing of functional objects that could be remotely melted and thereby removed using induction heating. The addition of monothiol was shown to decrease the polymer molecular weight which correspondingly increased the crystallization rate. Photopolymerization kinetics are independent of temperature while crystallization was slowed as the temperature approaches the melting point of the materials. Through inclusion of chromium oxide, semicrystalline materials could be melted through induction heating. These materials were implemented in vat photopolymerization 3D printing to realize high-resolution objects that could be used as releasable dental molds following printing and induction heating. This work demonstrates a proof-of-concept methodology to realize directly printable, thermally reversible semicrystalline materials for potential use as dental molding materials. [ABSTRACT FROM AUTHOR]

To facilitate the ongoing transition toward a circular economy, renewable 3D print materials that are both sustainable and competitive must be accessible. However, the growing demand for bio‐based thermosetting resins, which are used as ink for vat photopolymerization, gives rise to environmental concerns in terms of plastic waste management. Therefore, photocurable materials that are renewable and recyclable at the same time are needed. In this work, a mechanically robust and reprocessable 3D printed photopolymer is developed from renewable feedstock. Reaction of malic acid with glycidyl methacrylate introduces both methacrylate moieties that can undergo photopolymerization in the 3D printer, and β‐hydroxyester linkages that can act as dynamic crosslinks via bond exchange reactions. By combining modified malic acid with reactive diluents, a photoinitiator, and phosphate catalyst, three distinct resins are formulated, resulting in bio‐based contents ranging from 43% to 49%. The formulations demonstrate good layer fusion and accurate print quality, while the 3D printed specimens are robust and thermally stable. Notably, the printed object with shortest relaxation time displayed Arrhenius flow behavior with an activation energy of 36.0 kJ mol−1, and its mechanical performance is maintained after being recycled three times. This contributes to the end‐of‐life perspective of photocurable resins in additive manufacturing. [ABSTRACT FROM AUTHOR]

Here, methacrylated gelatin (GelMA) is obtained at different methacrylate anhydride concentrations (5.8% and 10% v/v), different reaction times (1 and 3 h), and under pH control. A ninhydrin test and nuclear magnetic resonance are used to determine the degree of functionalization (DoF) of the samples showing that pH controlling produces better functionalization degrees than an increase in methacrylate anhydride concentration or longer reaction times. The photopolymerization process of GelMA samples is studied by time‐resolved photoluminescence at different photoinitiator (PI) concentrations: 0.5%, 1%, and 2% w/v. An increase in PI concentration and DoF produces changes in the cross‐link. The 2% w/v concentration produces a higher reaction speed in the first 10 min and requires longer times to end the reaction. No significant differences are found in the use of smaller concentrations. [ABSTRACT FROM AUTHOR]

Vat photopolymerization holds promise for intricate ceramic structures through additive manufacturing. However, the scattering of ceramic pastes during printing can result in inaccuracies and defects. To address this, we propose utilizing a Monte Carlo method to account for scattering in absorbing media, predicting the curing profile of photopolymerizable ceramic suspensions. This method considers factors like the reflective air-slurry interface and the impact of particle size distributions on the curing profiles, which have been relatively overlooked in prior research. Employing physical equations, we developed a Matlab simulation program, facilitating the study of various process parameters on curing performance. The simulations accurately predict solidification width and depth for slurries with distinct volume fractions and powder particle sizes. The calculated correlation coefficient score was 0.9530 regarding curing depth in all six cases, significantly supporting the proposed method. Overall, this study underscores the potential of the Monte Carlo method in enhancing the precision of vat photopolymerization 3D printing for ceramics. • A Monte Carlo method is proposed to address scattering issues during vat photopolymerization 3D printing for ceramics. • The method considers reflective interface and particle size distributions, often overlooked in prior research. • Simulation shows accurate curing predictions, endorsing precision improvement in ceramic 3D printing [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]

The possibility of using a series of methacrylate-containing N,N-diethyl-4-(phenyldiazenyl)anilines with various para-substituents (–H, –Br, –NO2) relative to the azo group as photoinitiators of radical polymerization is considered. The electrochemical and photoluminescent properties of these compounds have been studied. In the presence of azo dyes, two-photon photopolymerization of pentaerythritol triacrylate was carried out using focused 780-nm radiation from a femtosecond laser. Structures with minimal dimensions of linear elements of 94 ± 5 nm were obtained by means of the DLW nanolithography technique, and 3D microstructures of complex architecture were fabricated. [ABSTRACT FROM AUTHOR]

Owing to the rapid advancement in electronic devices, thermal interface materials have been introduced to solve the thermal dissipation and electrical insulation problems in electronic parts and packaging materials. In this study, flexible thermally conductive acrylate‐based composites were fabricated via 3D vat photopolymerization. The effects of amine functional groups on the thermal and mechanical properties of acrylate polymers were explored. Surface‐treatment agents, namely, (3‐aminopropyl)triethoxysilane (APTES) and octadecylamine (ODA), were selected to enhance the poor dispersibility of fillers in the resin matrix caused by aggregation. The APTES‐treated carbon nanotube (CNT)–boron nitride (BN) hybrid composite exhibited the highest thermal conductivity of 0.990 W m−1 K−1, which was remarkably 482.35% higher than that of the matrix owing to the addition of 30 wt% BN, 0.5 wt% CNTs, and APTES treatment. The ODA‐treated CNT composite, which contained only 0.5 wt% CNTs, exhibited a thermal conductivity of 0.540 W m−1 K−1, which was 217.65% higher than that of the matrix. The electrical insulation properties of the composites were characterized, and the composites exhibited low electrical conductivity as electrical insulation materials. The advantages of the 3D‐printed flexible thermally conductive acrylate polymers usher in a new era of using polymer composites to address heat dissipation problems in complex structures. [ABSTRACT FROM AUTHOR]

This study evaluated the potential of gelatin methacryloyl (GelMA) for single-cell screening compared to polyethylene glycol diacrylate (PEGDA). GelMA photopolymerized at 1000–2000 mJ/cm2 produced consistent patterns and supported HeLa cell viability. GelMA (5%w/v) facilitated better cell collection within 2 days due to its shape retention. GelMA demonstrated biocompatibility with HeLa cells exhibiting exponential proliferation and biodegradation over 5 days. The average cell displacement over 2 days was 16 µm. Two targeted cell recovery strategies using trypsin were developed: one for adherent cells encapsulated at 800 mJ/cm2, and another for floating cells encapsulated at 800 mJ/cm2, enabling the selective removal of unwanted cells. These findings suggest GelMA as a promising biomaterial for single-cell screening applications, offering advantages over PEGDA in cell encapsulation and targeted recovery. [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]

Photopolymerization of thiol–epoxy resins initiated by photobase generators (PBGs) is a very good way to prepare specific polymeric products. However, the lack of near‐UV or visible light emitting diode (LED) light‐sensitive PBGs that can release strong bases to effectively catalyze this reaction and synchronously monitor the polymerization progress still is a problem. In this work, a series of such PBGs are successfully synthesized by modifying common aggregation‐induced emission (AIE) molecules, including triphenylamine and tetraphenylethylene and then neutralizing them with strong bases like 1,8‐diazabicyclo[5.4.0]undec‐7‐ene, 1,5‐diazabicyclo[4.3.0]non‐5‐ene, and 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD). The obtained PBGs show very good light absorption ability from 365 to 405 nm. They can generate free strong bases under near‐UV/visible LED light radiations as a result of photodecarboxylation reaction to catalyze the rapid thiol–epoxy photopolymerization. The TBD‐based PBGs have the best final monomer conversion above 60% due to their strongest alkalinity. Increasing viscosity during the polymerization process can trigger an AIE phenomenon of the PBGs. A linear correlation equation of the AIE intensity with the monomer conversion can be found, which is helpful for quantitatively monitoring the photopolymerization progress. More importantly, qualitative observations of the brightness changes of the resulting AIE lights are very useful to visualize the photopolymerization progress, which may find some applied potential in industry. [ABSTRACT FROM AUTHOR]

Abstract—The work is aimed at improvement of the mechanical properties of polymers produced using laser stereolithography technology by modifying the composition of a photocuring resin (PCR) with a highly dispersed filler. A composition based on vinyl ester resin was developed as the starting material, and aluminum hydroxide was chosen as the filler. The addition of the filler to the original PCR leads to a noticeable increase in the viscosity of the composition at 25°C. Specimens obtained both by laser stereolithography technology and by initiating polymerization by incoherent UV radiation were studied simultaneously for comparison. A thermomechanical analysis of the specimens was carried out and their studies were carried out using the differential scanning calorimetry method to determine the thermomechanical characteristics and the degree of conversion of double bonds for these specimens. It has been confirmed that post-curing of specimens is a necessary step in achieving their high mechanical properties. It has been shown that the use of aluminum hydroxide as a PCR filler improves the physicomechanical and thermomechanical properties of cured specimens. [ABSTRACT FROM AUTHOR]

The addition of static mixers within reactors leads to higher productivity of a process and an additional increase in mass and energy transfer. In this study, we developed millireactors with static mixers using stereolithography, an additive manufacturing technology. Computational fluid dynamics (CFD) simulations were conducted to study the flow, identify potential dead volumes, and optimize the design of the millireactors. We produced five millireactors with various static mixers and one tubular reactor without static mixers, which served as a reference. The Fenton reaction was performed as a model reaction to evaluate the performance of the millireactors. We observed that some of the reactors with static mixers had air plugs that created a significant dead volume but still exhibited higher conversions compared to the reference reactor. Our results demonstrate the potential of stereolithography for producing intricate millireactors with static mixers, which can enhance the productivity of chemical processes. [ABSTRACT FROM AUTHOR]

Decades of advances in understanding and simulating the polymerization kinetics and structural evolution that arises in free‐radical photopolymerizations of multifunctional monomers are combined into a single, first‐principles 3D model. The model explicitly accounts for polymerization features including diffusion‐controlled kinetics, oxygen inhibition, light attenuation, chain‐length dependent termination, reaction‐diffusion termination, heat transfer, composition and conversion‐dependent material properties, crosslinking effects, and species diffusion. Using the homopolymerization of 1,6‐hexanediol diacrylate as a model system, a minimum of two kinetics experiments performed at different initiation rates are required to fit model parameters. The model accurately predicts known relationships regarding oxygen inhibition, light intensity, and curing temperature for samples of different geometries and boundary conditions. The emphasis of the results herein is placed on the interactions between polymerization features, motivating the importance of a model that accommodates these features all in one simulation. The model is shown to be robust in its handling of thermal boundary conditions, alternative polymerization techniques or mechanisms, and characteristics of 3D voxel formation. The model in this work provides a useful tool for property prediction in a wide variety of applications, most notably coatings, dental materials, industrial photocuring processes, additive manufacturing, and holography, where complex interactions of the various features of polymerization play a substantial role. [ABSTRACT FROM AUTHOR]

This study presents a novel micellar cubic ionic liquid‐crystalline polymer electrolyte, featuring an alignment‐free spherical structure with unimpeded 3D ionic pathways, aimed at enhancing the performance of an ionic electroactive polymer actuator. The development involved creating a mechanically tough and high ion‐conductive cubic polymer film through the self‐assembly of a wedge‐shaped vinyl imidazolium salt and an imidazolium ionic liquid, followed by in situ photopolymerization. The 300 µm‐thick‐trilayer films, consisting of the cubic polymer electrolyte sandwiched between poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) electrodes, exhibit remarkable capabilities. These include bearing substantial loads of 4 g with a high blocking force under a DC voltage of 2 V, achieving a high bending strain of 0.63% under a low input voltage (±2 V, 0.1 Hz), and boasting a maximum response frequency of 70 Hz. These properties position the material for potential applications in soft robots and tactile sensing devices. [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]

Vat photopolymerization (VPP) based three‐dimensional (3D) printing, including stereolithography (SLA) and digital light projection (DLP), is known for producing intricate, high‐precision prototypes with superior mechanical properties. However, the challenge lies in the non‐recyclability of covalently crosslinked thermosets used in these printing processes, limiting the sustainable utilization of printed prototypes. This review paper examines the recently explored avenue of VPP 3D‐printed dynamic covalent network (DCN) polymers, which enable reversible crosslinks and allow for the reprocessing of printed prototypes, promoting sustainability. These reversible crosslinks facilitate the rearrangement of crosslinked polymers, providing printed polymers with chemical/physical recyclability, self‐healing capabilities, and degradability. While various mechanisms for DCN polymer systems are explored, this paper focuses solely on photocurable polymers to highlight their potential to revolutionize the sustainability of VPP 3D printing. [ABSTRACT FROM AUTHOR]

The problem of plastic waste in the environment calls for the development of new polymeric materials designed specifically for easy recycling at the end of their life cycle. Herein, a green polymer system comprising a series of necklace‐shaped polydimethylsiloxanes bearing anthracene dimer units is developed. The polymers have low environmental impact and are easily recycled. Further, their flexibility and glass transition temperatures are easy to control. These necklace‐shaped inorganic polymers are synthesized by photopolymerizing (dimerizing) anthracene‐terminated oligo‐dimethylsiloxane monomers. A key achievement of the present work is the successful chemical recovery of the monomers from the polymers through thermal depolymerization, enabling monomer–polymer recycling. By applying equilibrium polymerization with base catalysts, monomers with a controlled distributed chain length are synthesized from monomers with a constant chain length. The necklace‐shaped polymers synthesized from these randomized monomers have amorphous structures and readily form transparent films. It is possible to modulate the thermal and mechanical properties of the polymers by controlling the average chain length of the polydimethylsiloxane between the anthracene dimers. This investigation presents a method for the synthesis and cyclic utilization of polymer materials with a wide range of applications, including plastics and elastomers. [ABSTRACT FROM AUTHOR]

In this study, digital light processing (DLP) was utilized to generate 3D-printed blends composed of photosensitive acrylate-modified polylactic acid (PLA) resin mixed with varying weight ratios of lignin extracted from softwood, typically ranging from 5 wt% to 30 wt%. The microstructure of these 3D-printed blends was examined through X-ray microtomography. Additionally, the tensile mechanical properties of all blends were assessed in relation to the weight ratio and post-curing treatment. The results suggest that post-curing significantly influences the tensile properties of the 3D-printed composites, especially in modulating the brittleness of the prints. Furthermore, an optimal weight ratio was identified to be around 5 wt%, beyond which UV light photopolymerization experiences compromises. These findings regarding acrylate-modified PLA/lignin blends offer a cost-effective alternative for producing 3D-printed bio-sourced components, maintaining technical performance in reasonable-cost, low-temperature 3D printing, and with a low environmental footprint. [ABSTRACT FROM AUTHOR]

The development of additive manufacturing technique provides possibility to prepare SiC ceramics with complex shapes. However, defect control in the debinding and sintering stages is still a great challenge for the vat photopolymerized components. Here, SiC ceramics were manufactured by vat photopolymerization followed by liquid silicon infiltration, using SiC whiskers as the reinforcement. In the debinding stage, the SiC whiskers prevented the propagation of micro-cracks that induced by the formation and emission of gaseous substance. Also, the SiC whiskers provided channels for the infiltration of liquid silicon during sintering, thus the bulk density of the as-sintered SiC w /RBSC composite reached 2.95 g/cm3 at the whiskers fraction of 8 wt%. Because of the various toughening mechanisms introduced by SiC whisker, the flexural strength and Vickers hardness of the composite increased up to 352.2 MPa and 17.54 GPa, respectively. Thus, this work provides a new strategy to control micro-defects in vat photopolymerized SiC ceramics. [ABSTRACT FROM AUTHOR]

In this study, the vat photopolymerization (VP) additive manufacture technique was employed to fabricate Si 3 N 4 ceramics implants. A photosensitive suspension with a high solid loading of 40 vol% and a low viscosity of 1.95 Pa•s at a shear rate of 30 s−1 was achieved by optimization of the composition. Particularly, as high as 50 vol% content of PPG was used in the photosensitive suspension, leading to a smooth printing and increased debinding efficiency with a heating rate up to 3 °C/min. The printed body was sintered at 1800 °C under 0.4 MPa nitrogen atmosphere, obtained the Si 3 N 4 ceramic with a relative density of 96.08%, a fracture toughness of 5.88 MPa m1/2, a flexural strength of 677 MPa and a Vickers hardness of 16.26 GPa. A cylindric Si 3 N 4 ceramic implant was made by the optimized suspension and printing parameters, and the implantation test in the histological section was conducted, showing a good biocompatibility after 6 weeks. [ABSTRACT FROM AUTHOR]

Three‐Dimensional (3D) printed porous materials hold the potential for various soft sensing applications due to their remarkable flexibility, low density, and customizable geometries. However, developing versatile and efficient fabrication methods is crucial to unlock their full potential. A novel approach is introduced by combining Digital Light Processing (DLP) 3D printing and freeze‐drying to manufacture deformable cryogels featuring intricate morphologies. Photocurable hydrogels based on Poly(3,4‐ethylenedioxythiophene)Polystyrene sulfonate (PEDOT:PSS), Polyethylene glycol Diacrylate (PEGDA) and Ethylene Glycol (EG) are successfully printed and lyophilized. In this way, porous cryogels with tailorable properties are achieved. Microporosity varies from 68% to 96%, according to the chemical composition. Ultra‐soft cryogels with a compressive modulus of 0.13MPa are fabricated by adding a reactive diluent. As a result of the cryogelation process, which effectively removes water from the hydrogels, microporous structures with details as fine as 100 µm are obtained. The achieved freedom of design is exploited to fabricate resistive force sensors with a honeycomb lattice morphology. The sensitivity and the working range of the sensors can be tailored by tuning the size of the cells, paving the way for sensors with programmable architectures that can meet diverse requirements. [ABSTRACT FROM AUTHOR]

Vat photopolymerization (VP) additive manufacturing involves selectively curing low-viscosity photopolymers via exposure to ultraviolet light in a layer-wise fashion. Dispersing filler materials in the photopolymer enables tailored end-use properties, but also increases the viscosity and the timescale associated with interparticle network structural recovery postshear. These rheological properties influence self-leveling and recoating of the liquid photopolymer mixture during VP. Herein, viscosity of photopolymer and rigid spherical glass microparticles (filler) is experimentally determined as a function of filler fraction, filler size distribution (mono- and polydisperse), shear rate, and temperature, which are important VP process parameters. Employing existing viscosity models for monoand polydisperse polymer mixtures demonstrates that particle-particle interactions and the formation of nonspherical clusters of particles strongly affect the viscosity of both monodisperse and polydisperse mixtures with particle volume fractions >0.05 due to agglomeration/deagglomeration of clusters at elevated shear rates. Consequently, unmodified viscosity models, which assume uniformly dispersed, rigid, spherical particles, are applicable only for mixtures with particle volume fractions <0.05. It is shown that modifying model parameters such as the fluidity limit and intrinsic viscosity, which explicitly account for nonspherical clusters of particles, improves agreement between viscosity models and experiments, in particular when using a fractal approach. [ABSTRACT FROM AUTHOR]