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Thanks to the self-floating nature, hyperbranched-polysiloxane crosslinkers HPSis endows ionogels with gradient composition variation along the vertical direction, facilitating the prepared ionogels with gradient structures and properties. Gradient ionogels not only renders flexible sensors with dual-mode responses, but also enhances the sensitivity. The electrical signal of gradient-ionogel-based dual-mode flexible sensors can be wireless transmitted to a computer. [Display omitted] Monitoring complex human movements requires the simultaneous detection of strain and pressure, which poses a challenge due to the difficulty in integrating high stretchability and compressive ability into a single material. Herein, a series of hyperbranched polysiloxane crosslinkers (HPSis) with self-floating abilities are designed and synthesized. Taking advantage of the self-floating capabilities of HPSis, ionogels with gradient composition distribution and conductivities are constructed by in situ one-step photopolymerization, and possess satisfactory stretchability, high compressibility and excellent resilience. The gradient-ionogel-based strain sensor exhibits extraordinary pressure sensitivity (19.33 kPa−1), high strain sensitivity (GF reaches 2.5) and temperature sensing ability, enabling the monitoring of the angles and direction of joint movements, transmitting Morse code and wirelessly detecting bioelectrical signals. This study may inspire the design of development of multi-function flexible electronics. [ABSTRACT FROM AUTHOR]

Vat photopolymerization (VPP) printing of ceramic parts offers advantages such as low cost, simple operation, and short fabrication cycles. However, drawbacks include low toughness and brittleness in the printed parts. This study explores enhancing the toughness and strength of alumina (Al2O3) ceramics by incorporating silicon carbide (SiC) particles as additives. The impact of varying SiC contents on the quality of VPP‐printed Al2O3 parts is examined, encompassing microstructure, physical properties, and mechanical properties. Results indicate that optimal SiC addition reduces Al2O3 ceramics' porosity, enhances crystalline quality, and boosts mechanical properties. Excessive SiC, however, diminishes these benefits. The most significant strengthening of Al2O3 parts occurred with a 1.5 wt.% SiC content, increasing bending strength and fracture toughness by 239.7% and 564.7%, respectively. This underscore SiC's positive role in enhancing the quality of VPP‐printed Al2O3 parts. [ABSTRACT FROM AUTHOR]

Bioelectronics holds great potential as therapeutics, but introducing conductive structures within the body poses great challenges. While implanted rigid and substrate‐bound electrodes often result in inflammation and scarring in vivo, they outperform the in situ‐formed, more biocompatible electrodes by providing superior control over electrode geometry. For example, one of the most researched methodologies, the formation of conductive polymers through enzymatic catalysis in vivo, is governed by diffusion control due to the slow kinetics, with curing times that span several hours to days. Herein, the discovery of the formation of biocompatible conductive structures through photopolymerization in vivo, enabling spatial control of electrode patterns is reported. The process involves photopolymerizing novel photoactive monomers, 3Es (EDOT‐trimers) alone and in a mixture to cure the poly(3, 4‐ethylenedioxythiophene)butoxy‐1‐sulfonate (PEDOT‐S) derivative A5, resulting in conductive structures defined by photolithography masks. These reactions are adapted to in vivo conditions using green and red lights, with short curing times of 5–30 min. In contrast to the basic electrode structures formed through other in situ methods, the formation of specific and layered patterns is shown. This opens up the creation of more complex 3D layers‐on‐layer circuits in vivo. [ABSTRACT FROM AUTHOR]

Controlling the precision and mechanical cohesion of 3D-printed parts remains a central concern in the development of additive manufacturing. A two-dimensional finite element model of the photopolymerization of a complex sensitive resin, formulated with three monomers to better represent commercial resins, in a stereolithography apparatus is proposed as a tool for predicting and optimizing formulation of photosensitive resin and its printing parameters. By considering light illumination, chemical reaction, and heat transfer in a resin exposed to a moving ultraviolet (UV) laser source, this first approach accounts for monomer-to-polymer conversion and polymerization rate in agreement with experimental results obtained by Fourier-transform infrared spectroscopy (FT-IR) monitoring and the use of semi-empirical models. The temperature gradient along the exposed photosensitive material was also estimated. By varying the photoinitiator content and simulating the addition of an absorbing filler via the molar extinction coefficient, it was shown that a higher photoinitiator concentration and the presence of strongly absorbing fillers lead to a reduction in the light penetration depth, which can result in structural defects without adaptation of the layer thickness to be printed. [ABSTRACT FROM AUTHOR]

Ceramic vat photopolymerization (VPP) is a digital light processing method used to make additively manufactured green ceramic components that are then sintered. Despite the ever‐advancing maturation of this method's green‐state process, some of the material properties of sintered VPP‐processed ceramics are still not well defined or understood. One example is Mode I fracture toughness, KIc. In this study, attention was devoted to KIc measurement using net‐shape chevron‐notched bend bars that were VPP‐processed and the examination of whether valid KIc measurement could occur by testing them. Stable crack propagation was observed in >60% of tested samples, indicated by a smooth nonlinear transition through the measured maximum force prior to final fracture. However, their results cannot yet be responsibly referred to as KIc because of continuing violations of other prerequisites needed for valid KIc testing. [ABSTRACT FROM AUTHOR]

In the vat photopolymerization (VPP) 3D printing of ceramic cores, the solid loading is generally conducive to the microstructure and performance of products, owing to the improved bonding between adjacent layers and enhanced dimensional accuracy with increasing solid loading. In this work, the content of ceramic powder in photosensitive resin was optimized, the solid loading increased from 56 vol% to 68 vol%, and a novel curing model was established to explain the impact of solid loading on the printing precision. During sintering, the shrinkage is regulated to approximately 3 %, demonstrating a more homogeneous structure. The interlayer strength increased to 11.43 MPa while maintaining an apparent porosity of 23.47 %. Furthermore, the anisotropy of VPP-3D printed ceramic cores dependent on the solid loading was investigated. The ratio of vertical strength to horizontal strength (σ V /σ H) increased from 0.57 to 0.68 when the solid loading grew from 56 vol% to 68 vol%. At 1540 °C, the value of σ V /σ H was further enhanced to 0.81. This value met the precision casting criteria for ceramic cores effectively. This work can provide a reference for the investigation of high-solid-loading ceramic cores. [ABSTRACT FROM AUTHOR]

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]

Bio-derived monomers and biobased building blocks obtained from natural sources, e.g., fats and oils, are attracting increasing attention mainly due to sustainability concerns. Due to their features, renewable feedstocks are an excellent alternative to petroleum-based raw materials to shift towards greener chemistry, especially when coupled with energy-efficient processes like photopolymerization. In this review, we illustrate the recent research outcomes in the field of photocurable biobased monomers, showing the advantages of using biobased chemicals for the synthesis of photocurable monomers and the potential of naturally derived building blocks in photocuring reactions. [ABSTRACT FROM AUTHOR]

Silica particles were dispersed in 11 acrylic monomers at various concentrations. The dispersibility of the silica particles was evaluated based on the viscosity of the slurry. Furthermore, the relationship between the viscosity of the slurry and the solubility parameters (SPs) of the silica particles and acrylic monomers was investigated. When the SPs of the silica particles and acrylic monomers were close, the viscosity of the silica slurry decreased and high concentrations of the silica particles could be dispersed in the acrylic monomers. Therefore, SP can be used for predicting the dispersibility of silica particles. The prepared slurry was then used to fabricate sintered silica glass. Silica slurry was cured through photopolymerization to obtain a green body, which was then heat-treated at 850 °C in air atmosphere and sintered at 1710 °C under vacuum to obtain sintered silica glass. Transparent sintered silica glass with no cracks was obtained using 4-hydroxybutyl acrylate, which has a similar SP to that of silica particles, as a solvent. The obtained sintered silica glass exhibited a transmittance of 92 % at a wavelength of 400 nm. In the ultraviolet region, light absorption originated from two-coordinated Si in the glass. The absorption spectrum in the infrared region showed an extremely low peak of the SiOH group, indicating that low-OH silica glass was obtained. Thus, this study provides a new method for fabricating silica glass and provides a method of selecting solvents for the slurries used in powder sintering. [ABSTRACT FROM AUTHOR]

Featured Application: This study helps dental professionals select the most effective light-curing units for achieving optimal depth of cure in bulk-fill composites, enhancing the quality and longevity of dental restorations. This study aimed to evaluate the depth of cure (DoC) of bulk-fill composite resins, measured by the bottom-to-top Vickers microhardness ratio, using different light-curing units (LCUs): single-wave LED, polywave LED, and halogen. Six bulk-fill composites—Tetric EvoCeram Bulk Fill, X-tra base, SonicFill, Venus Bulk Fill, SDR, and Filtek Bulk Fill—were tested. Four LCUs, including one halogen (Elipar Trilight) and three LEDs (Demi Ultra, Valo, and Bluephase style), were employed for polymerization. Vickers hardness measurements were taken at depths of 1 mm to 5 mm. One- and two-way ANOVA (α = 0.05) were used for data analysis. The results revealed significant differences in microhardness and microhardness ratios among the composites at depths of 4 mm and beyond, depending on the LCU used. It was observed that most bulk-fill composites showed an adequate DoC up to 4 mm, but the effectiveness varied with different LCUs. Importantly, polywave LED LCUs did not exhibit a superior advantage in achieving depth of cure compared to monowave LED LCUs for composites containing multiple photoinitiators. These findings suggest that while several factors affect the DoC, the type of LCU plays a crucial role, and polywave LEDs may not offer additional benefits over monowave LEDs. [ABSTRACT FROM AUTHOR]

Vat photopolymerization is an additive manufacturing process for producing ceramics with high printing resolution. Extending this approach to multi-material additive manufacturing, the aim is to combine two or more different ceramics in a single component to aggregate their advantages. For this, binders for different ceramic materials are required. To enhance the debinding step, this work aimed to develop a versatile binder system suitable for different ceramic materials. Finally, a binder system was developed and qualified for several different ceramic materials. By thermogravimetrical analyses, a suitable temperature curve for debinding was derived. In a final sintering step, the components were densified almost defect-free. Therefore, this work serves as an enabler for multi-material vat photopolymerization. [ABSTRACT FROM AUTHOR]

Collecting fog water is crucial for dry areas since natural moisture and fog are significant sources of freshwater. Sustainable and energy-efficient water collection systems can take a page out of the cactus's playbook by mimicking its native fog gathering process. Inspired by the unique geometric structure of the cactus spine, we fabricated a bioinspired artificial fog collector consisting of cactus spines featuring barbs of different sizes and angles on the surfaces for water collection and a series of microcavities within microchannels inspired by Nepenthes Alata on the bottom to facilitate water flowing to the reservoir. However, replicating the actual shape of the cactus spine using conventional manufacturing techniques is challenging, and research in this area has faced a limitation in enhancing water-collecting efficiency. Here, we turned to 3D printing technology (vat photopolymerization) to create bio-mimetic fog collectors with a variety of geometric shapes that would allow for the most effective conveyance and gathering of water. Various barb sizes, angles between each barb in a single array, spine and barb arrangements, and quantity of barbs were tested experimentally and numeric analysis was carried out to measure the volume of water collected and optimize the mass rate. The result shows that optimal fog collection is with a mass flow rate of 0.7433 g/min, with Li = 900 μm, θ = 45°, ϕ = 90°, Nb = 2, and Ns = 5. This study presents a sustainable and ecologically sound method for efficiently collecting humid air, which is expected to be advantageous for the advancement of future-oriented fog-collection, water-transportation, and separation technologies. [ABSTRACT FROM AUTHOR]

Billions of patients struggle with dental diseases every year. These mainly comprise caries and related diseases. This results in an extremely high demand for innovative, polymer composite filling materials that meet a number of dental requirements. The aim of the study was to modify the light-cured composition of permanent dental fillings by changing the composition of the liquid organic matrix. New photoinitiators (DQ1-DQ5) based on a quinoline or quinoxaline skeleton and a co-initiator-(phenylthio)acetic acid (PhTAA) were used. In addition, monomers that have been traditionally used in dental materials were replaced by trimethylolpropane triacrylate (TMPTA). The neutral dental glass IDG functioned as an inorganic filler. The influence of the storage conditions of the developed composites in solutions simulating the natural oral environment during the consumption of different meals on sorption, solubility, and mass changes was assessed. For the tests, fifty-four cylindrical composite samples were prepared according to ISO 4049 guidelines and stored in different solutions. Distilled water, artificial saliva, heptane, 10% ethanol, and 3% acetic acid, as well as solutions containing pigments such as coffee, tea, red wine, and Coca-Cola, were used for the studies. The samples were stored in these solutions for 7, 14, 28, 35, 42, 49, 56, and 63 days at 37 °C. The sorption, solubility, and mass changes in the tested samples were determined, and the trend of these changes as a function of storage time was presented. The results were analyzed considering the nature of the solution used, i.e., aqueous, hydrophobic, and acidic. The properties evaluated changed in a different way, characteristic for each of the abovementioned solution groups. It was found that the type of solution simulating the natural environment of the oral cavity has the greatest influence on the sorption, solubility, and changes in the mass of the tested material. [ABSTRACT FROM AUTHOR]

The preparation of Si 3 N 4 ceramics by vat photopolymerization (VPP) has motivated increasing research interest. However, it is challenging to prepare Si 3 N 4 ceramics by VPP due to the high UV-light absorbance and refractive index of powder. In this paper, a method for Al 2 O 3 -coated Si 3 N 4 powder was proposed. Combined with the boehmite-coated and high-temperature treatment, Al 2 O 3 was successfully coated on the surface of Si 3 N 4 powder. The effect of Al 2 O 3 content on the properties of Si 3 N 4 powders, slurry and the sintered Si 3 N 4 samples were investigated. The Al 2 O 3 coating layer not only improves the curing forming ability of Si 3 N 4 slurries, but also can directly act as one of the sintering aids of Si 3 N 4 ceramics. The bulk density of the samples decreases from 3.04 ± 0.02 g/cm3 to 2.97 ± 0.01 g/cm3 with the increase of coating content, while the porosity increases from 5.38 ± 0.89 % to 7.54 ± 0.63 %. The sample of 5 wt % Al 2 O 3 coating content has the maximum flexural strength of 474.28 ± 16.38 MPa and the highest relative density of 94.62 ± 0.89 %. This work can not only obtain a great modification effect, but also promote the dense sintering of Si 3 N 4 ceramics during subsequent stages, which provides a constructive method for modifying Si 3 N 4 powders to achieve photopolymerization. [ABSTRACT FROM AUTHOR]

Porous Si 3 N 4 ceramics are widely applied in aerospace and mechanical fields owing to their excellent properties. Furthermore, vat photopolymerization (VPP) technology can fabricate Si 3 N 4 components with complicated structures and high precision, but its layer-by-layer printing method leads to poor mechanical properties of ceramics. In this study, porous Si 3 N 4 ceramics with a porosity of 28.41 % strengthened by directional β-Si 3 N 4 were fabricated by combining VPP technology and seeding method. Rheological behavior and curing properties of the slurry were explored, and the influence of β-Si 3 N 4 content on the mechanical properties of printed Si 3 N 4 ceramics was investigated systematically. With the increase of β-Si 3 N 4 content, the orientation degree of β-Si 3 N 4 grains increased gradually, while fracture toughness and flexural strength of the ceramics exhibited a trend of increased first and then decreased and Vickers hardness gradually decreased. As β-Si 3 N 4 content increased to 5 wt%, the fracture toughness and flexural strength of porous Si 3 N 4 ceramics were improved from 4.23 MPa m1/2 and 214.7 MPa–5.65 MPa m1/2 and 272.0 MPa, respectively. Therefore, this work indicates that vat photopolymerization combined with seeding method is a promising approach for the fabrication of porous Si 3 N 4 ceramics with high performance and complex structures. [ABSTRACT FROM AUTHOR]

Sustainability in additive manufacturing (AM) (3D printing) could play a pivotal role for manufacturers and producers in the next‐generation manufacturing framework. The market for 3D printing is expanding rapidly, and it is expected to do so in the foreseeable years to come. As ecologically, responsible manufacturing gains more attention, renewable substitutes for regular commercial 3D printable inks must be developed for lower environmental carbon footprints (less CO2 emissions, recycling, bio‐compatibility, and zero waste). Herein, we review the recent literature on using vegetable oil (VO) as bio‐based inks for sustainable formulations for digital light processing or stereolithography additive printing. The feedstock selections (VO, terpenes, and waste cooking oil), and the chemistry of the VO‐based synthons toward sustainability in the field of photopolymerization‐based 3D printing are discussed. These renewable materials can mitigate the detrimental environmental effects of AM while remaining competitive with the existing fossil‐based resins produced by industrial manufacturers. The current challenges and limitations of AM in terms of surface finish, material properties, photo‐curing time, and end‐of‐use recycling options from biomass‐derived photocurable monomers are also identified. Overall, this development promotes the bio‐based economy and allows for the on‐demand production of a variety of sustainable inks for AM and sustainable end‐of‐use products. Highlights: The significance of vegetable oils (VOs) as photopolymerizable monomers is explored.The necessity for 3D printing, specifically recycling and end‐of‐use, for the industrial revolution is provided.Green developments in stereolithography/digital light processing 3D printing utilizing VOs are covered. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) of polymers is a highly versatile technology that can be applied to many independent sectors like automotive, aviation, medicine, and dentistry. Since it has great potential for rapid prototyping, clean‐process concepts, and the ability to produce complex shapes, the layer‐by‐layer printing method is one of the most promising alternatives for future industrial production efforts. In that sense, different from the previous studies, this work aims to elucidate the friction and wear properties of the special dental samples manufactured via photopolymerization‐based AM technology according to both for printing parameters, and dry sliding test variables. Also, this is the first initiation to examine the combined influences of the UV exposure time, building direction, and sliding force on the surface roughness, hardness, friction coefficient, wear rate, and main plastic damage mechanism of the printed samples. The results showed that the maximum average hardness value was detected as 89.8 Shore D for vertically built samples printed with 8 s exposure time. In addition, vertically printed samples exhibited better wear resistance than the horizontal samples and the rising exposure time generally affected affirmatively the hardness levels of the samples. The lowest volume loss of 78 mm3 belonged to the vertical sample at 5 N. Further, increasing test force levels caused a decrease in the friction coefficient results and triggered the volume loss increase in the samples. Among all samples, the calculated friction coefficient values changed between 0.3 and 0.87. On the other side, scanning electron microscopy (SEM), and energy‐dispersive spectroscopy (EDS) analyses pointed out that ascending exposure times led to the altering contact surface matchings determining the final volume loss outcomes. Highlights: To obtain better surface quality, vertical printing was a useful option.Horizontally printed samples exhibited higher friction coefficients.Curing time positively impacted the wear resistance for both orientations.Grooves and debris parts were observed on surfaces with low exposure times. [ABSTRACT FROM AUTHOR]

In the field of regenerative medicine, acrylated epoxidized vegetable oils are emerging as a promising avenue of exploration. The aim of this study is to evaluate the degradability of two formulations of acrylated epoxidized soybean oil (AESO): pure AESO and AESO diluted with soybean oil (SO) for potential bioprintability applications. The comprehensive investigation of these two polymeric formulations included optimization of polymerization conditions, confirmation of cytocompatibility, and, most importantly, the study of their degradability. The results reveal that AESO, used as a biomaterial for biomedical applications, undergoes a distinctive degradation process, combining both enzymatic and oxidative degradation (AESO/SO samples lose 29.45% of their weight after 60 days). This phenomenon is the result of a complex interplay of factors, including the chemical composition and physical characteristics of the polymer, the unique tissue environment in which it is implanted, and the duration of implantation. [ABSTRACT FROM AUTHOR]

In the present study, we focused on the development and characterization of formulations that function as biological inks. These inks were doped with coumarin derivatives to act as molecular luminescent sensors that allow the monitoring of the kinetics of in situ photopolymerization in 3D (DLP) printing and bioprinting using pneumatic extrusion techniques, making it possible to study the changes in the system in real time. The efficiency of the systems was tested on compositions containing monomers: poly(ethylene glycol) diacrylates and photoinitiators: 2,4,6-trimethylbenzoyldi-phenylphosphinate and lithium phenyl-2,4,6-trimethylbenzoylphosphinate. The selected formulations were spectroscopically characterized and examined for their photopolymerization kinetics and rheological properties. This is important because of the fact that spectroscopic characterization, examination of photopolymerization kinetics, and rheological properties provide valuable insights into the behaviour of photocurable resin dedicated for 3D printing processes. The next step involved printing tests on commercially available 3D printers. In turn, printing carried out as part of the work on commercially available 3D printers further verified the effectiveness of the formulations. Moreover the formulation components and the resulting 3D objects were tested for their antiproliferative effects on the selected Chinese hamster ovary cell line, CHO-K1. [Display omitted] • Bioinks doped with luminescent sensors for in situ photopolymerization monitoring. • Applications of bioinks at DLP and pneumatic extrusion 3D printing technique. • Cytotoxicity of the sensors in the tested range has not been indicated. • Intense Vis-LED radiation (405 nm) does not have a damaging effect on cells. [ABSTRACT FROM AUTHOR]

(1) Background: This study investigates the effects of curing light intensity, exposure time, and distance on the Vickers microhardness (VMH), hardness bottom-to-top ratio (HR), and temperature rise (TR) of conventional dental resin-based composite (RBC). (2) Materials and Methods: Specimens of one conventional RBC (Tetric EvoCeram, Ivoclar Vivadent) were cured with 12 different curing protocols (CPs), created with three different light intensities (Quartz Tungsten Halogen 300 mW/cm2, LED 650 mW/cm2, LED 1100 mW/cm2), two exposure times (20 and 40 s), and two distances of curing tip (0 and 8 mm). The VMH of top (VMH-T) and bottom (VMH-B) surfaces was measured. The hardness bottom-to-top ratio (HR) was calculated from VMH-B and VMH-T. The HR below 80% was rated as inadequate polymerization. The TR at the depth of 2 mm within the RBC was measured using a K-type thermocouple. Data were analyzed using Levene's test and the multivariate analysis of variance (MANOVA). The level of significance was set at p < 0.05. (3) Results: Exposure time and distance significantly influenced VMH-B and HR. Increased distance significantly reduced VMH-B, HR, and TR. CPs 300 mW/cm2/8 mm/20 s and 650 mW/cm2/8 mm/20 s produced inadequate polymerization (HR < 80%). Prolonged exposure time produced higher values of VMH-B and HR. The TR was significantly influenced by light intensity and distance. (4) Conclusions: Suboptimal light intensity (<800 mW/cm2) can produce inadequate polymerization at the lower side of the composite layer when used from a distance. Prolonged irradiation can improve the polymerization to a certain extent. Clinicians are advised to monitor the intensity of the LCUs in order to optimize the photopolymerization process. Caution is required when polymerizing with high-intensity curing light in direct contact with the RBC with longer exposure times than recommended. [ABSTRACT FROM AUTHOR]

The prime objective of the current investigation is to develop a methodology of hybrid additive manufacturing (HAM), which is an amalgamation of vat photopolymerization (VPP) based 3D printing and pressureless sintering, for the fabrication of Ti6Al4V parts for biomedical applications. In this study, the effect of a wide range of sintering temperatures (1200 to 1600 °C), heating rate (2 to 4 °C/min), and holding time (60 to 180 minutes) has been considered. Further, the effect of process variables on three responses, namely porosity, shrinkage, and compressive yield strength, are investigated. It is found that sintering temperature is the most significant process variable, followed by heating rate and holding time, influencing all three responses. With an increase in sintering temperature, porosity reduces while shrinkage and compressive yield strength increase. Further, fabricated specimens are characterized using XRD and EDS analysis. XRD analysis confirms the existence of both α and β-phases, and EDS analysis negates any possibility of significant contamination during sintering. Microstructure evolution from SEM micrographs suggests significant neck growth and densification, with fully connected pores, which ensures good bonding between powder particles. The present investigation's outcome helps develop porous near-net shape complex parts for biomedical applications. [ABSTRACT FROM AUTHOR]

Phenacyl bromide has been explored as a new Norrish Type I photoinitiator for radically polymerizing methyl methacrylate and styrene monomers. A straightforward radical photopolymerization method using UVA light for the synthesis of chain-end functional poly(methyl methacrylate) and polystyrene has been developed. The process has been refined for both bulk and solution photopolymerizations. Chain-end functionalization was demonstrated by the formation of block-copolymers of the bromine-ended homopolymers, utilized as macroinitiators, resulting in an increase in the molecular weight of the corresponding precursor, observed by gel permeation chromatography (GPC). Block copolymerization was initiated by radicals generated at the chain-ends by a halogen-atom transfer reagent, namely, dimanganese decacarbonyl (Mn2(CO)10). This simple light-induced method is promising for the additive manufacturing field such as vat photopolymerization, stereolithography, digital light processing as it yields chain-end functional materials that can be further processed. Table of Contents (TOC). [ABSTRACT FROM AUTHOR]

Vat photopolymerized 3D printing technology can be used to fabricate ceramics with complex shapes. However, the extensive use of photosensitive resins as binders is not conducive to achieving crack-free ceramic green parts, especially the Si 3 N 4 ceramics with the weak interlayer bonding. In this work, the influence of different debinding atmosphere on the pyrolysis process of organics in vat photopolymerization 3D printed Si 3 N 4 green parts was investigated. The results showed that the use of 95 vol% N 2 +5 vol% H 2 atmosphere can effectively inhibit the cracking during the debinding process, especially the wall thickness of the 3D printed defect-free Si 3 N 4 green body was successfully increased to 5 mm, and the obtained sintered Si 3 N 4 ceramics exhibited higher true densities and better mechanical properties. The debinding atmospheres proposed in the current work provided additional options of debinding atmosphere for achieving high-performance 3D printed Si 3 N 4 ceramics and are expected to be expanded to other photosensitive slurry systems, with the potential to enable the production of ceramic components with the larger wall thicknesses. [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]

Injectable and temperature-responsive Poly(N-Isopropylacrylamide) (PNIPAAm)/Chitosan composite hydrogels reinforced with cellulose nanocrystals (CNCs) were successfully fabricated via photopolymerization. 0.1–3% (w/v) of cellulose nanocrystals were incorporated into the PNIPAAm/chitosan matrix to form thermo-responsive injectable composite hydrogels. FT-IR spectra confirmed the successful formation of these hydrogels, highlighting the characteristic peaks PNIPAAm, chitosan and CNCs. The inclusion of CNCs led to a reduced pore size as compared to the control hydrogels. The mechanical properties of the hydrogel were characterized under various temperature conditions. Rheology tests showed that storage modulus (G′) increased significantly above 30 °C, indicating gel-like behavior. Thermogravimetric analysis showed thermal stability up to 300 °C. The volume phase transition temperatures (VPTT) of the hydrogels were found to be in the range of 34–38 °C, close to physiological body temperature. The equilibrium swelling ratio (ESR) of the CNC-containing hydrogels was higher than that of the control. In vitro studies with Human Dermal Fibroblast adult (HDFa) cells showed the hydrogels to be non-toxic, suggesting their potential for biomedical applications. [ABSTRACT FROM AUTHOR]

A 3D-printable polymer can provide an effective solution for developing piezoelectric structures. However, their nanocomposite formulation and 3D printing processability must be optimized for fabricating complex geometries with high printability. In the present study, we optimized the 3D-printable piezoelectric composite formulation for developing complex geometries by an additive manufacturing approach. The zinc oxide (ZnO) nanomaterial was synthesized by the hydrothermal method. The ZnO loading in the 3D-printed flexible resin was optimized to exhibit good interfacial adhesion and enable 3D printing. The lattice structure was fabricated to improve the piezoelectric response compared with the solid structure. The lattice structure block printed with 10 wt% ZnO showed a good piezoelectric response, with a linear increase in the generated output voltage for an increase in force. The maximum power density of 0.065 μW/cm2 was obtained under 12 N force at 1 Hz. The fabricated structure generated a peak–peak voltage of ~3 V with a foot heel strike. [ABSTRACT FROM AUTHOR]

Poly(vinyl alcohol) (PVA) based hydrogels have gained more interest in the field of biomaterials because of their many biomedical uses (i.e., wound healing, drug delivery, and tissue engineering) and intrinsic physicochemical and biological characteristics. They can be made using a variety of synthetic techniques, but all of them are very time-consuming. Among them, photopolymerization also referred to as light-induced polymerization, has drawn a lot of attention because of its benefits, which include not requiring the use of solvents, easy and quick network formation, energy efficiency, quick processing, control over both space and time and reliability of crosslinking density and matrix strength. Ultraviolet (UV)-curable hydrogels containing PVA as a main component are gaining interest because of their excellent properties, including biodegradability, biocompatibility, less cytotoxicity and remarkable mechanical strength. This review highlights the significance of UV curable systems and their components, types, advantages and disadvantages of photoinitiators (PIs), UV curable monomers and their structures, properties of UV-cured PVA hybrid hydrogels, and their characterizations and applications in different fields. The photopolymerization mechanisms, tunable properties, and unique advantages of these hydrogels have been explored in detail. Furthermore, it sheds light on recent advancements in PVA-based hydrogels research and future exploration in this domain. [ABSTRACT FROM AUTHOR]

The need for rapid, on-site contaminant detection is becoming increasingly vital for tackling environmental and public health challenges. This study introduces an efficient method for detecting sulfamethoxazole (SMX), a widely used antibiotic with significant environmental implications. A cost-effective, scalable approach was developed using lab-on-paper devices integrated with molecularly imprinted polymers (MIPs), synthesized through an in situ photopolymerization process that was completed in just 10 min. Using only 2 mL of MIP solution enabled the efficient mass production of 100 disks. Traditional template extraction, which often takes hours or days, was reduced to just 10 min using a multichannel micropipette and absorbent fabric. The MIP-PAD achieved a limit of detection (LOD) of 0.8 µg/mL and a limit of quantification (LOQ) of 2.4 µg/mL, with measurements obtained using a smartphone-based colorimetric detection system. It exhibited excellent repeatability, with a relative standard deviation (RSD) of 3.26% across seven tests, high reusability for up to eight cycles, and recovery rates for real samples ranging from 81.24% to 99.09%. This method provides notable improvements in sensitivity, reproducibility, and environmental sustainability over conventional techniques. The user-friendly platform integrating smartphone-based colorimetric detection is highly practical for real-time applications, offering broad potential for environmental monitoring, food safety, and healthcare. [ABSTRACT FROM AUTHOR]

Current additive manufacturing (AM) techniques and methods, such as liquid-crystal display (LCD) vat photopolymerization, offer a wide variety of surface-sensing solutions, but customizable internal sensing is both scarce in presence and narrow in scope. In this work, a fabrication process for novel customizable embedded ceramic temperature sensors is investigated. The fabrication techniques and materials are evaluated, followed by extensive characterization via spectral analysis and thermomechanical testing. The findings indicate that LCD-manufactured ceramic sensors exhibit promising sensing properties, including strong linear thermal sensitivity of 0.23% per °C, with an R2 of at least 0.97, and mechanical strength, with a hardness of 570 HV, making them suitable for adverse environmental conditions. This research not only advances the field of AM for sensor development but also highlights the potential of LCD technology in rapidly producing reliable and efficient ceramic temperature sensors. [ABSTRACT FROM AUTHOR]

This paper introduces an approach to preparing high‐strength Si3N4 ceramics using vat photopolymerization with a bi‐phase particle size gradation strategy. The influence of different ratios of coarse β‐Si3N4 powders (Cβ) and fine α‐Si3N4 powders (Fα) on the slurry performance, microstructure evolution, and final ceramic strength was systematically studied. It was found that an appropriate particle size gradation can significantly reduce the viscosity of the slurry. The curing depth of Si3N4 slurries decreases with increasing Fα content, while the stability increases. During sintering, dissolved Fα‐Si3N4 not only directly precipitates into small elongated β‐Si3N4 grains but also onto the neighboring Cβ‐Si3N4, promoting the development of large elongated β‐Si3N4 grains and resulting in a bimodal microstructure distribution. The highest strength of Si3N4 ceramics was achieved with a ratio of 6:4 Cβ to Fα Si3N4 powders. Under these conditions, the Si3N4 ceramics exhibited a flexural strength of 472 MPa, significantly higher than that of Si3N4 ceramics prepared using pure Cβ/Fα powders. The strength improvement is primarily due to the well‐designed bi‐phase particle size gradation strategy, which optimizes slurry performance, minimizes defects that may be introduced during the green part printing process while controlling the microstructure evolution during sintering, achieves the ideal bimodal microstructure distribution. The outcomes of this research demonstrate the feasibility of using vat photopolymerization with bi‐phase particle size gradation for the preparation of high‐strength Si3N4 ceramics, which has great potential for application in the manufacturing of various ceramic products. [ABSTRACT FROM AUTHOR]

Producing ceramic parts by Vat Photopolymerization (VPP) additive manufacture with desired mechanical properties typically requires time‐consuming debinding steps. This study aims at optimizing composition and processing parameters with the use of dibutyl phthalate (DBP) in the resin formulation and debinding in an argon atmosphere for dental zirconia‐toughed alumina (ZTA). The method produces parts with fewer defects, and 67.7% higher flexural strength while increasing the debinding heating rate over 400% compared to standard formulations debinded in air. These improvements are attributed to pore formation at low temperatures and reduced heat release and gas evolution rates arising from use of the DBP and the inert atmosphere, respectively. While ZTA ceramics were studied, this method should be applicable to many ceramic systems with exciting possibilities for promoting the rapid development of VPP 3D‐printed high‐performance ceramics for various engineering applications. [ABSTRACT FROM AUTHOR]

We report the results of an international interlaboratory study of the flexural strength of alumina fabricated across six laboratories using the vat photopolymerization ceramic additive manufacturing (AM) technology. The mechanical testing of all the specimens, 142 in total, was performed at the National Institute of Standards and Technology (NIST) according to the well‐established four‐point bending method standardized for traditional ceramics. Overall, the existing ASTM standard for the four‐point bend testing proved adequate for AM ceramics, with several modifications to the specimen requirements to account for the specifics of AM processes. Critical flaws that caused failure were identified in all but two cases using optical fractography augmented with the imaging of fracture surfaces in a scanning electron microscope. The flexural strength data, analyzed following the Weibull statistics, exhibited considerable variation among the specimen sets manufactured by different laboratories. This variability correlated with the presence of many distinct critical flaws. We identified seven types of flaws that accounted for the failure of 94% of specimens. The prevalent flaws depend on the printing direction relative to the specimen's geometry. We discuss the nature of these flaws and their relation to the printing and post‐processing conditions. Removal of several types of critical flaws will significantly improve mechanical properties of ceramic parts built using vat‐photopolymerization AM. [ABSTRACT FROM AUTHOR]

[Display omitted] The skin has a multilayered structure, and deep-seated injuries are exposed to external microbial invasion and in vivo microenvironmental destabilization. Here, a bilayer bionic skin scaffold (Bilayer SF) was developed based on methacrylated sericin protein to mimic the skin's multilayered structure and corresponding functions. The outer layer (SF@TA), which mimics the epidermal layer, was endowed with the function of resisting external bacterial and microbial invasion using a small pore structure and bio-crosslinking with tannic acid (TA). The inner layer (SF@DA@Gel), which mimics the dermal layer, was used to promote cellular growth using a large pore structure and introducing dopamine (DA) to regulate the wound microenvironment. This Bilayer SF showed good mechanical properties and structural stability, satisfactory antioxidant and promote cell proliferation and migration abilities. In vitro studies confirmed the antimicrobial properties of the outer layer and the pro-angiogenic ability of the inner layer. In vivo animal studies demonstrated that the bilayer scaffolds promoted collagen deposition, neovascularization, and marginal hair follicle formation, which might be a promising new bionic skin scaffold. [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]

As the metal additive manufacturing (AM) field evolves with an increasing demand for highly complex and customizable products, there is a critical need to close the gap in productivity between metal AM and traditional manufacturing (TM) processes such as continuous casting, machining, etc., designed for mass production. This paper presents the development of the scalable and expeditious additive manufacturing (SEAM) process, which hybridizes binder jet printing and stereolithography principles, and capitalizes on their advantages to improve productivity. The proposed SEAM process was applied to stainless steel 420 (SS420) and the processing conditions (green part printing, debinding, and sintering) were optimized. Finally, an SS420 turbine fabricated using these conditions successfully reached a relative density of 99.7%. The SEAM process is not only suitable for a high-volume production environment but is also capable of fabricating components with excellent accuracy and resolution. Once fully developed, the process is well-suited to bridge the productivity gap between metal AM and TM processes, making it an attractive candidate for further development and future commercialization as a feasible solution to high-volume production AM. [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]

This study investigates the synthesis, characterization, and antimicrobial properties of hydrogels synthesized through the UV-pulsed laser photopolymerization of a polymer–photoinitiator–chlorpromazine mixture. Chlorpromazine was used for its known enhanced antimicrobial properties when exposed to UV laser radiation. The hydrogel was formed from a mixture containing 0.05% Irgacure 2959, 10% gelatin methacryloyl, and various concentrations of chlorpromazine (1, 2, and 4 mg/mL). Laser-induced fluorescence spectroscopy was employed to monitor the photoinduced changes of chlorpromazine and Irgacure 2959 during hydrogel formation, providing insight into the photodegradation dynamics. FTIR spectroscopy confirmed the incorporation of irradiated chlorpromazine within the hydrogel matrix, while the release profiles of chlorpromazine showed sustained release only in hydrogels containing 1 mg/mL of CPZ. The hydrogel showed significant antimicrobial activity against MRSA bacteria when compared to that of penicillin. These findings highlight the potential of CPZ loaded during the photopolymerization process into hydrogels as effective antimicrobial agents with sustained release properties, making them suitable for combating resistant bacterial strains. [ABSTRACT FROM AUTHOR]

NIR‐induced upconversion‐assisted photopolymerization has gained growing attention in the past two decades because of its numerous advantages over conventional UV/visible photopolymerization and two‐photon polymerization processes. However, research in this area is still in its early stages. To extend the practical application of NIR‐induced radiation curing, it is essential to optimize the factors affecting the photopolymerization reactions. Researchers have been constantly trying to improve these factors to tune the photo‐physical characteristics (luminescence intensity and color) of upconversion particles (UCPs), enhance curing depths and degree of double bond conversion (DC), and investigate the application of UCPs in emerging fields. In this review, first, a brief discussion of the upconversion mechanisms and upconversion efficiency is provided. Then, a detailed discussion of the factors influencing the upconversion‐assisted photopolymerization comprising UCP nature and characteristics, UCP content, presence of fillers/pigments/additives, laser intensity, photoinitiator content, and maximum absorption wavelength of photoinitiator is provided, and recent progress in improving these factors is presented. Finally, the advantages and drawbacks of the UC‐initiated polymerization are discussed, and perspectives for future directions are suggested. Highlights: NIR‐induced upconversion‐assisted photopolymerization garners growing interest.Influential factors in upconversion‐assisted photopolymerization are thoroughly discussed.The recent progress on improving these factors and the future directions are provided. [ABSTRACT FROM AUTHOR]

Tuberculosis (TB) is the top cause of death from a single infectious pathogen after COVID-19. Despite molecular diagnostic advances, two-thirds of the 10 million annual TB cases are still diagnosed using direct smear microscopy which has ~50% sensitivity. To increase the analytical performance of smear microscopy, we developed and characterized a novel polymer (Polydiallyldimethylammonium chloride [PDADMAC]) engraftment on inexpensive polystyrene (PS) specifically functionalized for mycobacterial capture. Engraftment is achieved via UV photopolymerization of DADMAC monomer on plasma-activated PS. The platform was tested on sputum from presumptive TB cases in Kampala, Uganda (n = 50), with an increased overall sensitivity of 81.8% (27/33) vs. fluorescent smear microscopy 57% (19/33) compared to a molecular (Cepheid GeneXpert MTB/RIF) gold standard. Frugal smear diagnostic innovation that is rapid and does not require dedicated instrumentation may offer an important solution to bridge the TB diagnostic gap. [ABSTRACT FROM AUTHOR]

Vat photopolymerization 3D printing provides a novel approach for preparing broadband wave-transparent Si 3 N 4 /β-SiAlON composite ceramics. This paper oxidized raw powder to introduce low dielectric phases (SiO 2) and overcome the low curing depth of α-Si 3 N 4. The solid content of oxidized α-Si 3 N 4 was increased to 50 vol% for the first time by modification with dispersant. The selected print thickness of 50 μm was the highest known for Si 3 N 4 vat photopolymerization 3D printing, greatly improving printing efficiency. Finally, Si 3 N 4 /β-SiAlON composite ceramics were sintered in the range of 1600-1800 °C, and the mechanical and dielectric properties were systematically studied. The composite ceramics sintering at 1780 °C had a maximum bending strength of 236 ± 16 MPa, and the real permittivity was 4.83. At 1800 °C the porosity increased resulting in bending strength decreased to 109 ± 4 MPa, and the real permittivity to 3.23. This study filled the gap in the post-treatment of oxidized α-Si 3 N 4 and guided the application of Si 3 N 4 /β-SiAlON composite ceramics in the field of wave-transparent. [ABSTRACT FROM AUTHOR]

Polymerization in the solid state is generally infeasible due to restrictions on mobility. However, in this work, the solid‐state photopolymerization of crystalline dicyclopentadiene is demonstrated via photoinitiated ring‐opening metathesis polymerization. The source of mobility in the solid state is attributed to the plastic crystal nature of dicyclopentadiene, which yields local short‐range mobility due to orientational degrees of freedom. Polymerization in the solid state enables photopatterning, volumetric additive manufacturing of free‐standing structures, and fabrication with embedded components. Solid‐state photopolymerization of dicyclopentadiene offers a new paradigm for advanced and freeform fabrication of high‐performance thermosets. [ABSTRACT FROM AUTHOR]

This study proposes a new, doubly re-entrant auxetic unit-cell design that is based on the widely used auxetic honeycomb structure. Our objective was to develop a structure that preserves and enhances the advantages of the auxetic honeycomb while eliminating all negative aspects. The doubly re-entrant geometry design aims to enhance the mechanical properties, while eliminating the buckling deformation characteristic of the re-entrant deformation mechanism. The effects of the geometric modification are described and evaluated using two parameters, offset and deg. A series of experiments were conducted on a wide range of parameters based on these two parameters. Specimens were printed via the vat photopolymerization process and were subjected to a compression test. Our aim was to investigate the mechanical properties (energy absorption and compressive force) and the deformation behaviour of these specimens in relation to the relevant parameters. The novel geometry achieved the intended properties, outperforming the original auxetic honeycomb structure. Increasing the offset and deg parameters results in increasing the energy absorption capability (up to 767%) and the maximum compressive force (up to 17 times). The right parameter choice eliminates buckling and results in continuous auxetic behaviour. Finally, the parameter dependency of the deformation behaviour was predicted by analytical approximation as well. [ABSTRACT FROM AUTHOR]

A novel photopolymerizable (meth)acrylate oligomer syrup modified with ferulic acid (FA) was verified as an antimicrobial coating binder against a biofilm of Staphylococcus epidermidis. A solution-free UV-LED-initiated photopolymerization process of aliphatic (meth)acrylates and styrene was performed to prepare the oligomer syrup. The influence of ferulic acid on the UV crosslinking process of the varnish coatings (kinetic studies using photo-DSC) as well as their chemical structure (FTIR) and mechanical (adhesion, hardness), optical (gloss, DOI parameter), and antibacterial properties against S. epidermidis were investigated. The photo-DSC results revealed that FA has a positive effect on reducing the early occurrence of slowing processes and has a favorable effect on the monomer conversion increment. It turned out, unexpectedly, that the more FA in the coating, the greater its adhesion to a glass substrate and hardness. The coating containing 0.9 wt. part of FA exhibited excellent antimicrobial properties against S. epidermidis, i.e., the bacterial number after 24 h was only 1.98 log CFU/mL. All the coatings showed relatively high hardness, gloss (>80 G.U.), and DOI parameter values (30–50 a.u.). [ABSTRACT FROM AUTHOR]

Photopolymerization is becoming increasingly popular in industry due to its copious advantages. The vital factor in the entire pre-polymerization formulation is the presence of photoinitiators. Depending on the application, photoinitiators have different features. Hence, scientists are particularly interested in developing new photoinitiators that can expand the scope of applications and be used to create products with the features demanded by current trends. This brief review summarizes the photoinitiators used in dental materials and hydrogels and those obtained from natural and synthetic sources. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing is an innovative manufacturing method with the potential to revolutionize topical and transdermal dosage forms. Nowadays, it is established that Vatbased photopolymerization (VP) 3D printing technologies offer superior printing efficiency and versatility compared to other 3D printing technologies available on the market. However, there are some limitations that impair their full application in pharmaceutical contexts, such as the lack of a range of biocompatible materials for topical and transdermal applications. This review article explores all types of VP-based 3D printing and discusses the relevance of implementing this kind of technology. We start with a detailed description of the printing process, focusing on the commercial materials available and lab-made resins proposed by different authors. We also review recent studies in this field, which mainly focus on the fabrication of transdermal devices based on microneedle arrays. In the future, it is expected that the manufacturers of 3D printers invest in modifications to the printing apparatus to allow the simultaneous printing of different resins and/or compound types, which will open frontiers to the personalization of treatment approaches. [ABSTRACT FROM AUTHOR]