Digital Light Processing 3D Printing Research Articles

Numerical and experimental investigation of 3D printed tunable stiffness metamaterial with real-time response using digital light processing technology

A tunable mechanical metamaterial is a type that can be altered or manipulated to change its physical properties in various situations. This study introduces a novel type of metamaterial, hydro-tunable metamaterials (HTMs), which can be dynamically adjusted in real-time by filling or draining it with water. The development of HTMs has significant implications for various fields, including mechanical engineering, biomedical applications, and energy absorption. The study involves designing and manufacturing HTMs using a Digital Light Processing (DLP) 3D printing process. The design process involves modifying an initial basic auxetic structure to create a closed and sealed structure accommodating fluid. The printed samples are then characterized using mechanical testing and finite element analysis (FEA). Experiments and simulations have found that a sample containing water behaves differently from a sample without water, resulting in an increase in stiffness. This difference can be leveraged to modify the stiffness and strength of the structure. This phenomenon is attributed to the incompressibility of water within the structure. Water exerts a hydrostatic pressure on the auxetic material, resulting in increased stiffness and resistance to compression. This technique highlights the potential of HTMs to be dynamically adjusted in real-time, leading to enhanced energy absorption and improved performance. An additional FEA was conducted to examine the impact of water pressure on the mechanical behavior of the structure. The results indicate that applying pressure or temperature to the water can significantly enhance the mechanical properties of the water-filled sample.

Engineering fully quaternized (Dimethylamino)ethyl methacrylate-based photoresins for 3D printing of biodegradable antimicrobial polymers

Nowadays, medical devices or implants are widely used in the medical field to treat different diseases. However, bacterial infections are one of the significant problems associated with medical devices and are recognized as a concern in healthcare worldwide. Addressing this problem has driven the exploration of new materials with potent antibacterial properties. In this regard, quaternary ammonium compounds (QACs), which are organic salts with an alkane chain and a charged part of quaternary ammonium groups, came up with a potent antibacterial activity. Herein, we report for the first-time dimethylamino ethyl methacrylate (DMAEM) derived quaternary ammonium monomer and crosslinker to prepare photoresins for DLP (Digital light processing) 3D printing. The structure of the synthesized monomer and crosslinker was confirmed via FTIR (Fourrier Transform Infrared) and 1H NMR (Hydrogen Nuclear Magnetic Resonance) while the physicochemical properties of the 3D printed polymer were investigated using TGA (Thermogravimetric Analysis), DSC (Differential Scanning Calorimeter) and UTM (Universal testing machine). By optimizing the printing conditions and monomer to crosslinker ratio, we can print high-resolution 3D-printed objects. Additionally, in vitro biodegradation, cytocompatibility, and hemocompatibility tests revealed that the printed polymers are biodegradable, cytocompatible, and hemocompatible in nature. More importantly, the printed polymers exhibited strong antibacterial activity against both gram-negative and gram-positive bacteria, suggesting their potential utility in personalized antibacterial medical devices.

(Alumina and graphene)/ PLA nanocomposites manufactured by digital light processing 3D printer

In this study, the variant effects of alumina and graphene reinforcing nanoparticle percentages on the tensile and wear properties of the nanocomposites, produced using digital light processing (DLP), were determined by employing SEM images of fracture and worn surfaces to introduce a hybrid (alumina + graphene)/PLA nanocomposite with desirable wear and mechanical properties. With the addition of alumina up to 2 wt%, the tensile strength was initially decreased exhibiting a rapid brittle fracture over the flat fracture surface. However, with a continued increase in the amount of reinforcing particles, the tensile strength eventually increased by 16% compared to the pure resin sample at 8 wt% of alumina while changing the fracture mode with plenty of cleavages accompanied by crack deflections. The specific wear rate in the 8 wt% alumina sample decreased by almost 62% compared to the pure resin sample. Graphene caused a significant drop in tensile strength due to the generation of cavities and porosities around the graphene agglomerates, but it greatly improved the wear properties, with the specific wear rate decreasing by almost 77% at just 1 wt%. Then hybrid nanocomposites of alumina and graphene reinforcements were produced with the aim of optimal tensile and wear properties. The 0.5% graphene +3.5% alumina improved the wear resistance and provided moderate tensile properties; however, the 1% graphene +3% alumina could not increase the wear resistance due to the weakening of graphene plates sticking to the polymer substrate.

Evaluation of zirconia ceramics fabricated through DLP 3d printing process for dental applications

Zirconia ceramics are versatile materials with remarkable properties such as a high thermal resistance, high fracture strength, and low thermal conductivity. They are chemically inert and highly wear- and corrosion-resistant, making them ideal for a wide range of applications in the aerospace, automotive, and biomedical fields. In dentistry, zirconia ceramics are used for veneers, crowns, bridges, and implants because of their biocompatibility. Despite the various benefits of zirconia ceramics, they are difficult to process because of their high hardness and brittleness. Additive manufacturing (AM) has proven to be a viable alternative to conventional fabrication processes, particularly for the processing of difficult-to-cut materials. AM of ceramics has gained significant attention in recent years because of its flexibility and ability to produce customized geometries rapidly and economically. In this study, the digital light processing (DLP) technique was employed to 3D print yttria-stabilized zirconia. The fabricated zirconia was evaluated and characterized for use in dental applications. Thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) were performed on the green body to assess the decomposition of the additives in the slurry and determine the debinding temperatures. The as-built parts were subjected to debinding and sintering to obtain fully dense zirconia parts. The parts tended to shrink after sintering; therefore, the shrinkage ratios were evaluated and found to be 1.2817, 1.2900, and 1.3388 in the x-, y-, and z-directions, respectively. The average density after sintering was 6.031 g/cc. The flexural strength determined using four-point bending tests was 451.876 MPa, and the tensile and compressive strengths were 143 MPa and 298.4 MPa, respectively.

3D printed UV-sensing optical fiber probes: manufacturing, properties, and performance

UV sensing 3D printed optical fiber hydrogels provide a flexible and precise method of remotely of detecting exposure to UV radiations. The optical fibers were created using digital light processing 3D printing technique with hydrogel composites, including micro-sized photochromic dyes (pink, blue and their combination). When exposed to ultraviolet (UV) radiation, these dyes exhibited specific absorption characteristics, resulting in significant decreases in both reflection and transmittance mode spectra at 560 nm, 620 nm, and 590 nm. Optical fibers of lengths 1, 2, and 3 cm were manufactured in two orientations: vertical and horizontal. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were utilized to characterize the printed fiber probes. The optical performance of the fibers was tested using customized measurement setups. The reflection and transmission of the printed fibers reduced as the length increased due to optical losses. Reflection and transmisson loss of 20–40% can be observed when the length is increased from 1 to 3 cm. The maximum loss in reflection is observed for pink fiber in the presence of UV irradiation. Also, the type of powder used impacted the response and retraction time, whereas the mixed fiber showed the highest response time of 12–20 s under various conditions. The pink dye added fiber probes shows quick response to UV radiation. An increase in the response time is observed with increasing fiber length. The impact of printing orientation on the transmission and reflectance mode operations of optical fibers was assessed. In addition, the stability of the fiber probes are assesed using a green laser having wavelength 532 nm. This work comprehensively examines the optical properties, manufacturing procedures, and sensing capacities of UV-sensitive photochromic optical fiber sensors.

Fabrication of High-Density Microarchitected Tungsten via DLP 3D Printing.

Current additive manufacturing (AM) techniques for tungsten, such as powder bed fusion and directed energy deposition, often generate parts with rough surfaces. Vat photopolymerization presents a promising alternative for fabricating tungsten structures with high shape fidelity and low surface roughness. However, existing vat photopolymerization approaches suffer from surface defects and low final density, leading to compromised mechanical properties. Therefore, achieving high-density tungsten structures using vat photopolymerization remains a crucial challenge. This work presents a straightforward and reliable method for fabricating complex, micro-architected tungsten structures with superior density and hardness. The approach utilizes a water-based photoresin with exceptional tungsten ion loading capacity. The photoresin is then patterned using digital light processing (DLP) to create tungsten-laden precursors. A three-step debinding and sintering process subsequently achieves 3D tungsten structures with dense surface morphology and minimal internal defects. The microstructures achieve a minimum feature size of 35µm, a low surface roughness of 2.86µm, and demonstrate exceptional mechanical properties. This new method for structuring tungsten opens doors to a broad range of applications, including micromachining, collimators, detectors, and metamaterials.

Bio-based ester- and ester-imine resins for digital light processing 3D printing: The role of the chemical structure on reprocessability and susceptibility to biodegradation under simulated industrial composting conditions

Four biobased ester and ester-imine photocurable resins were formulated and evaluated for printability by digital light processing 3D printing. The resin formulations consisted of methacrylated eugenol alone or in combination with methacrylated poly(hydroxybutyrate)-oligomers and/or methacrylated vanillin-derived Schiff-base monomers. It was not possible to print methacrylated eugenol alone into coherent thermosets, likely due to the lower reactivity of the allyl-double bond. However, in combination with the other building blocks methacrylated eugenol improved the printability, although some over-curing phenomena were registered especially for the resins composed of methacrylated eugenol and methacrylated poly(hydroxybutyrate)-derived oligomers. The three formulations that were successfully printed to coherent thermosets were further evaluated for their solvent resistance, thermal and mechanical properties, reprocessability and biodegradability under simulated industrial composting conditions. The reprocessing experiments documented the synergic effect of ester and imine dynamic covalent bonds in favoring the preservation of the elastic modulus of the thermosets; while an evidently higher deterioration of the mechanical properties was registered for the ester-thermosets. The biodegradation studies highlighted a clear correlation between the biodegradation rate and the chemical structure of the thermosets, with the aliphatic components and ester and imine bonds increasing the thermosets’ susceptibility to the biodegradation under simulated industrial composting conditions.

3D-printing inherently MRI-visible accessories in aiding MRI-guided biopsies

Background3D printers have gained prominence in rapid prototyping and viable in creating dimensionally accurate objects that are both safe within a Magnetic Resonance Imaging (MRI) environment and visible in MRI scans. A challenge when making MRI-visible objects using 3D printing is that hard plastics are invisible in standard MRI scans, while fluids are not. So typically, a hollow object will be printed and filled with a liquid that will be visible in MRI scans. This poses an engineering challenge however since objects created using traditional Fused Deposition Modeling (FDM) 3D-printing techniques are prone to leakage. Digital Light Processing (DLP) is a relatively modern and affordable 3D-printing technique using UV-hardened resin, capable of creating objects that are inherently liquid-tight. When printing hollow parts using DLP printers, one typically requires adding drainage holes for uncured liquid resin to escape during the printing process. If this is not done liquid resin will remain inside the object, which in our application is the desired outcome.PurposeWe devised a method to produce an inherently MRI-visible accessory using DLP technology with low dimensional tolerance to facilitate MRI-guided breast biopsies.MethodsBy hollowing out the object without adding drainage holes and tuning printing parameters such as z-lift distance to retain as much uncured liquid resin inside as possible through surface tension, objects that are inherently visible in MRI scans can be created without further post-processing treatment.ResultsObjects created through our method are simple and inexpensive to recreate, have minimal manufacturing steps, and are shown to be dimensionally exact and inherently MRI visible to be directly used in various applications without further treatment.ConclusionOur proposed method of manufacturing objects that are inherently both MRI safe, and MRI visible. The proposed process is simple and does not require additional materials and tools beyond a DLP 3D-printer. With only an inexpensive DLP 3D-printer kit and basic cleaning and sanitation materials found in the hospital, we have demonstrated the viability of our process by successfully creating an object containing fine structures with low spatial tolerances used for MRI-guided breast biopsies.

Parametric design and performance evaluation of TPMS porous vitrified bond diamond grinding wheel using digital light processing

Porous vitrified bond diamond grinding wheels are commonly used for grinding hard and brittle materials. However, uneven pore distribution and low porosity affect the grinding performance of the wheel significantly. In this study, three types of triply periodic minimal surface porous vitrified bond diamond grinding wheels—Gyroid, Diamond, and Lidinoid–were prepared through parametric designing and digital light processing 3D printing. The grinding wheel achieved a uniform distribution and an interconnected pore structure. The key to high-performance grinding wheel via stereolithography 3D printing lies in the preparation of the slurry with high solid loading, low viscosity and uniform stability. Hence, the effect of surface modifiers on the slurry, along with the effect of sintering temperature and the microscopic and mechanical properties, was investigated. By grinding the SiC ceramics, the material removal rate, grinding temperature, and surface roughness were compared to those achieved using a conventional solid-structure grinding wheel. The results show that the slurry with the highest solid content of 80 wt% (58 vol%) and viscosity of 4.21 Pa s (30 s−1) can be prepared using surface-modified particles. The diamond grinding wheel sintered at 680 °C exhibits the best comprehensive performance. A grinding wheel prepared using stereolithography 3D printing can achieve better surface roughness and lower the grinding temperature.

Biocompatibility and customizability: Expanding possibilities with 3D printed guide cannulas

BackgroundIntracerebral cannulation bypasses the blood-brain barrier, and is frequently used for targeted drug delivery to specific brain structures. Despite the availability of brain infusion kits and manual injections without cannulation, the traditional design of guide cannulas continues to be utilized in research. Several protocols describing guide cannula manufacture from stainless steel needles have been published previously. New methodWe describe a method for producing the first fully plastic guide cannula intended for intracerebroventricular injections in mice using Dental Sand A1-A2 resin and digital light processing 3D printing. ResultsThe lack of resin neurotoxicity for primary rat cortical neuron cultures was shown. Histological evaluations performed 6 weeks after guide cannula implantation to C57/black mice show that plastic cannula are biocompatible. Microglial and astroglial reactions to plastic cannulas are reduced compared to lab-made stainless steel cannulas. Plastic cannulas are less prone to obstruction, and remained unobstructed over the course of 3 weeks of daily injections, while 50 % of stainless steel cannula became impassable by the 2 week mark. Comparison with existing methodsThese are the first published cannulas intended for applications in mice which combine the presence of usable threads, allowing dummy cannula fixation, with a low profile and small footprint compared to commercially available cannulas. ConclusionsEditable parametric and stl files for reproducing the cannulas presented in this manuscript are included. The method described in this paper is accessible to most laboratories, enabling near-perfect standardization in length combined with a high level of customizability.

Effect of 3D printing technology and print orientation on the trueness of additively manufactured definitive casts with different tooth preparations

ObjectivesTo evaluate the fabrication trueness of additively manufactured maxillary definitive casts with various tooth preparations fabricated with different 3-dimensional (3D) printers and print orientations. MethodsA maxillary typodont with tooth preparations for a posterior 3-unit fixed partial denture, lateral incisor crown, central incisor and canine veneers, first premolar and second molar inlays, and a first molar crown was digitized with an industrial scanner. This scan file was used to fabricate definitive casts with a digital light processing (DLP) or stereolithography (SLA) 3D printer in different orientations (0-degree, 30-degree, 45-degree, and 90-degree) (n = 7). All casts were digitized with the same scanner, and the deviations within each preparation site were evaluated. Generalized linear model analysis was used for statistical analysis (α = 0.05). ResultsThe interaction between the 3D printer and the print orientation affected measured deviations within all preparations (P ≤ 0.001) except for the lateral incisor crown and canine veneer (P ≥ 0.094), which were affected only by the main factors (P < 0.001). DLP-90 mostly led to the highest and DLP-0 mostly resulted in the lowest deviations within posterior tooth preparations (P ≤ 0.014). DLP-30 led to the lowest deviations within the first premolar inlay and DLP-45 led to the lowest deviations within the central incisor veneer preparation (P ≤ 0.045). ConclusionsPosterior preparations of tested casts had the highest trueness with DLP-0 or DLP-30, while central incisor veneer preparations had the highest trueness with DLP-45. DLP-90 led to the lowest trueness for most of the tooth preparations. Clinical Significance:Definitive casts with tooth preparations fabricated with the tested DLP 3D printer and the print orientation adjusted on tooth preparation may enable well-fitting restorations. However, 90-degree print orientation should be avoided with this 3D printer, as it led to the lowest fabrication trueness.

Research on additive manufacturing technology of high solid loading silica glass slurry

In this work, digital light processing (DLP) 3D printing technology was used to fabricate transparent silica glass with complex structures. The effects of different particle sizes and mixing ratios of silica powders on the viscosity of the prepared slurries were investigated. The results showed that when 100–200 nm and 800 nm silica powders were mixed in a 1:4 vol ratio, the slurry exhibited the lowest viscosity. The highest solid loading of the slurry prepared with this mixed silica powder reached 75 wt%, with a viscosity of only 1245 mPa·s. The high solid loading slurry was subjected to 3D printing, debinding, and sintering treatment, and the transparent silica glass samples with complex structures was obtained.

Fabrication of Ruby by 3D printing of transparent salt solutions

A novel method is presented for fabricating 3D-printed Cr3+-doped α-Al2O3 complex structures, known as Ruby, using digital light processing (DLP) 3D printing and sol-gel reactions based on solutions only. The aqueous printing solution comprises aluminum and chromium chloride as the sol-gel precursor and acrylic acid (AA) as the polymerizable component. After photopolymerization, aging, and sintering at 1150°C, structures shrink up to 28±7 %, achieving a final printing resolution of 55.7±0.7 μm, surpassing the nominal printer’s resolution of 200 μm. Characterization includes X-ray diffraction, scanning electron microscopy, UV-Vis, and fluorescence measurements, revealing crystalline Cr:α-Al2O3 composition emitting at 693 nm. The structures exhibit maximum compression stress of 89±3 MPa and microhardness of 340–500 HV, showcasing potential applications in thermal insulation, jewelry, and mechanical uses.

Sustainable Light‐Assisted 3D Printing of Bio‐Based Microwave‐Functionalized Gallic Acid

AbstractThe development of 3D printing technologies and the requirement for more sustainable 3D printing materials is constantly growing. However, ensuring both sustainability and performance of the new materials is crucial to replace current fossil‐based polymers. Here, a bio‐based UV‐curable resin is produced in high yield from gallic acid (GA), a natural polyphenolic compound, by means of rapid and efficient microwave‐assisted methacrylation (5 min heating time and 10 min at 130 °C). The successful microwave‐assisted methacrylation with a high degree of substitution is confirmed by Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance spectroscopy. The radical UV‐photopolymerization of the methacrylated gallic acid (MGA) is further investigated by real‐time FTIR and differential scanning photo calorimetry (photo‐DSC) analyses, clearly demonstrating the high photo‐reactivity of MGA. Moreover, the %gel assessment demonstrates the formation of highly insoluble fractions after the UV‐curing, with 98% gel content. The photo‐rheology and rheology support the suitability of MGA for light‐assisted 3D printing. Indeed, a honeycomb and a hollow cube are 3D printed by means of the digital light processing 3D printing technique with high accuracy in a small scale. Finally, the cured‐MGA illustrates high Tg and thermal stability.

Onium Photocages for Visible-Light-Activated Poly(thiourethane) Synthesis and 3D Printing.

The lack of chemical diversity in light-driven reactions for 3D printing poses challenges in the production of structures with long-term ambient stability, recyclability, and breadth in properties (mechanical, optical, etc.). Herein we expand the scope of photochemistries compatible with 3D printing by introducing onium photocages for the rapid formation of poly(thiourethanes) (PTUs). Efficient nonsensitized visible-light photolysis releases organophosphine and -amine derivatives that catalyze thiol-isocyanate polyaddition reactions with excellent temporal control. Two resin formulations comprising commercial isocyanates and thiols were developed for digital light processing (DLP) 3D printing to showcase the fast production of high-resolution PTU objects with disparate mechanical properties. Onium photocages represent valuable tools to advance light-driven manufacturing of next-generation high-performance sustainable materials.

3D-Bioprinted Gelatin Methacryloyl-Strontium-Doped Hydroxyapatite Composite Hydrogels Scaffolds for Bone Tissue Regeneration.

New gelatin methacryloyl (GelMA)-strontium-doped nanosize hydroxyapatite (SrHA) composite hydrogel scaffolds were developed using UV photo-crosslinking and 3D printing for bone tissue regeneration, with the controlled delivery capacity of strontium (Sr). While Sr is an effective anti-osteoporotic agent with both anti-resorptive and anabolic properties, it has several important side effects when systemic administration is applied. Multi-layer composite scaffolds for bone tissue regeneration were developed based on the digital light processing (DLP) 3D printing technique through the photopolymerization of GelMA. The chemical, morphological, and biocompatibility properties of these scaffolds were investigated. The composite gels were shown to be suitable for 3D printing. In vitro cell culture showed that osteoblasts can adhere and proliferate on the surface of the hydrogel, indicating that the GelMA-SrHA hydrogel has good cell viability and biocompatibility. The GelMA-SrHA composites are promising 3D-printed scaffolds for bone repair.

Vat photopolymerization 3D printing of biobased low viscosity photoactive benzoxazine thermosets

Preparing biobased benzoxazine resin through vat photopolymerization 3D printing is of great significance for its sustainable development and application in cutting-edge fields. In this work, biobased guaiacol and eugenol are used as phenol sources, while 2-(2-aminoethoxy) ethanol with flexible ether bonds is used as an amine source to create photoactive benzoxazine monomers, Eu-BzMA and Gu-BzMA. The viscosity of both monomers at room temperature is lower than 150 mPa·s, which can satisfy the requirements of digital light processing (DLP) 3D printing without adding diluents. The thermal and mechanical properties of the 3D printing benzoxazine resins are studied and the relationship between structure and properties is discussed by comparing the two molecules. Eu-BzMA resin has higher thermal decomposition temperature (T5 = 343 °C), higher hardness (0.70 GPa), higher flexural stress (43.5 MPa) and flexural moduli (2.71 GPa); while, Gu-BzMA resin has higher glass transition temperature (176 °C). This is because Eu-BzMA resin shows higher cross-linking density, but contains more flexible structures formed by allyl crosslinking. In this article, a preparation strategy of low viscosity biobased photoactive benzoxazine is proposed and successfully applied to vat photopolymerization 3D printing.

Digital Light 3D Printing of Double Thermoplastics with Customizable Mechanical Properties and Versatile Reprocessability.

Digital light processing (DLP) is a 3D printing technology offering high resolution and speed. Printable materials are commonly based on multifunctional monomers, resulting in the formation of thermosets that usually cannot be reprocessed or recycled. Some efforts are made in DLP 3D printing of thermoplastic materials. However, these materials exhibit limited and poor mechanical properties. Here, a new strategy is presented for DLP 3D printing of thermoplastics based on a sequential construction of two linear polymers with contrasting (stiff and flexible) mechanical properties. The inks consist of two vinyl monomers, which lead to the stiff linear polymer, and α-lipoic acid, which forms the flexible linear polymer via thermal ring-opening polymerization in a second step. By varying the ratio of stiff and flexible linear polymers, the mechanical properties can be tuned with Young's modulus ranging from 1.1GPa to 0.7MPa, while the strain at break increased from 4% to 574%. Furthermore, these printed thermoplastics allow for a variety of reprocessability pathways including self-healing, solvent casting, reprinting, and closed-loop recycling of the flexible polymer, contributing to the development of a sustainable materials economy. Last, the potential of the new material in applications ranging from soft robotics to electronics is demonstrated.

A poly(L-lactic Acid)-based flexible piezoelectric energy harvester with micro-zigzag structures

Piezoelectric energy harvester (PEH) holds great potential for flexible electronics and wearable devices. However, the power conversion efficiency of flexible PEH (fPEH) has often been a limiting factor, especially under variable excitation. Herein, we propose a practical solution: a poly(L-lactic acid)-based fPEH with 3D-printed micro-zigzag structures. This design not only broadens the operational bandwidth and enhances low-frequency response but also offers a tangible improvement in the power conversion efficiency of fPEH. The micro-zigzag structure was designed and fabricated using a digital light processing 3D printing technique with acrylates, a method that is readily accessible to researchers and engineers in the field. Mechanical properties of the 3D-printed acrylic elastomers with different compositions were investigated to obtain the material parameters, and then fPEH with the sandwich structure was fabricated via sputtering and packaging. Subsequently, numerical simulation was conducted on the micro-zigzag structures to determine the structure sizes and oscillation frequencies of fPEH. Finally, four micro-zigzag structures with 3-, 4-, 5- and 6 mm lengths were tested to obtain oscillation frequencies of 51, 37, 22, and 21 Hz consistent with the simulation. The output voltages of fPEH are 11–30 mV with the load ranges of 60–100 MΩ. Stability evaluation showed that the fPEH can work under low frequency (<100 Hz) and broadband conditions. The micro-zigzag structure provided new insights for the design of fPEH, paving the way for more efficient and practical energy harvesting solutions in the future.

Carbazole-fused coumarin bis oxime esters (CCOBOEs) as efficient photoinitiators of polymerization for 3D printing with 405 nm LED

In this research, the innovative design and successful synthesis of two visible light photoinitiators, namely CCOBOE0 and CCOBOE1, have been confirmed through nuclear magnetic resonance (NMR) and mass spectrometry (MS). Both compounds exhibit strong absorption properties at 385, 405 and 450 nm, and FT-IR analyses have substantiated the ability of CCOBOE1 to initiate the polymerization of a trifunctional acrylate monomer (TMPTA) under these three light sources. The optimal conditions for maximizing the photoinitiation potential of CCOBOE1 were determined to be at a concentration of 2 × 10−5 mol.g−1 and under 405 nm LED irradiation. Photolysis experiments, theoretical calculations, detection of CO2 absorption peaks, and ESR experiments have all confirmed the generation of methyl radicals by CCOBOE1. Utilizing the identified optimal conditions, a “XYZ” pattern with a thickness of 963 μm and a 3D-object were successfully obtained via direct laser write (DLW) and digital light processing (DLP) 3D-printing upon irradiation at 405 nm. Additionally, differential scanning calorimetry (DSC) analyses demonstrated the promising performance of CCOBOE1 in initiating the thermal polymerization of acrylate monomers. In summary, the difunctional CCOBOE1 showed outstanding performance in both photo-initiation and thermal initiation of acrylate monomers. It provides a novel direction for the development of novel OXEs with dual activation modes.