Three-dimensional Printing Technique Research Articles

Miniaturized reconfigurable three dimensional printed frequency selective surface based microwave absorbers

ABSTRACT A unique strategy for the design of reconfigurable microwave absorbers based on the frequency selective surface (FSS) concept is presented in this paper. Three different topologies are considered (namely, Structure A, B, and C), and their resonance frequencies are varied by increasing the height and subsequently changing the capacitance value, with the help of a modular interlocking block system. This reconfigurability further reduces the electrical size of the absorber structures, thereby leading to miniaturization. Structure A has an absorption frequency switching from 4.89 GHz to 2.26 GHz (with a 53.7% miniaturization). Similarly, Structure B has a frequency range between 2.98 and 1.89 GHz, leading to a size reduction of 36.5%, whereas the frequency shift is observed in Structure C from 2.25 GHz to 1.79 GHz (with a shift of 20.4%). The absorptivity curves in L, S, and C bands for various structures are unaltered by variation in polarization and incident angle (up to 30 degrees), indicating polarization-insensitive and angularly stable responses. Impedance responses (real and imaginary) are also evaluated to justify the absorption characteristics. The proposed structures are fabricated using the three-dimensional (3D) printing technique, and their test results are consistent with the simulated responses.

Challenges faced with 3D-printed electrochemical sensors in analytical applications.

Prototyping analytical devices with three-dimensional (3D) printing techniques is becoming common in research laboratories. The attractiveness is associated with printers' price reduction and the possibility of creating customized objects that could form complete analytical systems. Even though 3D printing enables the rapid fabrication of electrochemical sensors, its wider adoption by research laboratories is hindered by the lack of reference material and the high "entry barrier" to the field, manifested by the need to learn how to use 3D design software and operate the printers. This review article provides insights into fused deposition modeling 3D printing, discussing key challenges in producing electrochemical sensors using currently available extrusion tools, which include desktop 3D printers and 3D printing pens. Further, we discuss the electrode processing steps, including designing, printing conditions, and post-treatment steps. Finally, this work shed some light on the current applications of such electrochemical devices that can be a reference material for new research involving 3D printing.

3D Printing of a Porous Zn-1Mg-0.1Sr Alloy Scaffold: A Study on Mechanical Properties, Degradability, and Biosafety.

In recent years, the use of zinc (Zn) alloys as degradable metal materials has attracted considerable attention in the field of biomedical bone implant materials. This study investigates the fabrication of porous scaffolds using a Zn-1Mg-0.1Sr alloy through a three-dimensional (3D) printing technique, selective laser melting (SLM). The results showed that the porous Zn-1Mg-0.1Sr alloy scaffold featured a microporous structure and exhibited a compressive strength (CS) of 33.71 ± 2.51 MPa, a yield strength (YS) of 27.88 ± 1.58 MPa, and an elastic modulus (E) of 2.3 ± 0.8 GPa. During the immersion experiments, the immersion solution showed a concentration of 2.14 ± 0.82 mg/L for Zn2+ and 0.34 ± 0.14 mg/L for Sr2+, with an average pH of 7.61 ± 0.09. The porous Zn-1Mg-0.1Sr alloy demonstrated a weight loss of 12.82 ± 0.55% and a corrosion degradation rate of 0.36 ± 0.01 mm/year in 14 days. The Cell Counting Kit-8 (CCK-8) assay was used to check the viability of the cells. The results showed that the 10% and 20% extracts significantly increased the activity of osteoblast precursor cells (MC3T3-E1), with a cytotoxicity grade of 0, which indicates safety and non-toxicity. In summary, the porous Zn-1Mg-0.1Sr alloy scaffold exhibits outstanding mechanical properties, an appropriate degradation rate, and favorable biosafety, making it an ideal candidate for degradable metal bone implants.

Engineering tools for stimulating wound healing

Wound healing is the complex physiological process of restoring the skin's integrity, structure, and function after damage caused by external conditions. The wound healing cascade may be altered due to the progression of certain diseases, such as diabetes, venous hypertension, or peripheral arterial disease, resulting in non-healing chronic wounds. Chronic wounds can be characterized by a wide variety of pathologies including increased reactive oxygen species, ineffective neutrophil activity, overabundance of pro-inflammatory cytokines, and chronic hypoxia. Medical intervention is crucial to heal chronic wounds. This review explores current research to engineer improved chronic wound treatment devices, dressings, and constructs to facilitate tissue regeneration and wound closure. This review first covers different physical stimulation therapies, then, local therapeutic delivery systems, and finally three-dimensional (bio)printing techniques for the fabrication of skin grafts and wound dressings. Additionally, the review discusses the regulatory process for bringing cutting-edge wound healing technologies to market and highlights currently approved products for wound treatment. At the end, the unmet need and future directions that the field should expand are discussed.

Processing, Microstructure, and Performance of Robocast Clay-Based Ceramics Incorporating Hollow Alumina Microspheres.

The restoration of ancient ceramics has attracted widespread attention as it can reveal the overall appearance of ancient ceramics as well as the original information and artistic charm of cultural relics. However, traditional manual restoration is constrained due to its time-consuming nature and susceptibility to damaging ancient ceramics. Herein, a three-dimensional (3D) printing technique was employed to accurately restore Chinese Yuan Dynasty Longquan celadon using hollow Al2O3 microsphere-modified 3D printing paste. The results show that the hollow Al2O3 microsphere content plays a vital role in the printability, physical properties, and firing performance of the modified 3D printing paste. The printed green bodies show no noticeable spacing or voids under moderate rheological conditions. The as-prepared ceramic body modified with 6 wt.% hollow Al2O3 microspheres and fired at 1280 °C exhibits optimal bending strength of 56.66 MPa and a relatively low density of 2.16 g∙cm-3, as well as a relatively uniform longitudinal elastic modulus and hardness along the interlayer. This 3D printing technique based on hollow Al2O3 microsphere-modified paste presents a promising pathway for achieving non-contact and damage-free restoration of cultural relics.

Three-Dimensional Printing of Drug-Eluting Implantable PLGA Scaffolds for Bone Regeneration.

Despite rapid progress in tissue engineering, the repair and regeneration of bone defects remains challenging, especially for non-homogenous and complicated defects. We have developed and characterized biodegradable drug-eluting scaffolds for bone regeneration utilizing direct powder extrusion-based three-dimensional (3D) printing techniques. The PLGA scaffolds were fabricated using poly (lactic-co-glycolic acid) (PLGA) with inherent viscosities of 0.2 dl/g and 0.4 dl/g and ketoprofen. The effect of parameters such as the infill, geometry, and wall thickness of the drug carrier on the release kinetics of ketoprofen was studied. The release studies revealed that infill density significantly impacts the release performance, where 10% infill showed faster and almost complete release of the drug, whereas 50% infill demonstrated a sustained release. The Korsmeyer-Peppas model showed the best fit for release data irrespective of the PLGA molecular weight and infill density. It was demonstrated that printing parameters such as infill density, scaffold wall thickness, and geometry played an important role in controlling the release and, therefore, in designing customized drug-eluting scaffolds for bone regeneration.

3D printing for the reinterpretation of architectural heritage: Proposal of a model

3D printing for the reinterpretation of architectural heritage stands out as one of the most efficient ways of using contemporary printing technologies in terms of architecture. The aim of the study is to present a comprehensive methodology on how to use 3D printing techniques for reinterpretation of architectural heritage. In this context, the scope of the study consists of pioneering information obtained from literature studies focusing on the details of the use of three-dimensional printing techniques in the promotion, preservation and remodeling of cultural heritage and architectural heritage components. The method of the study was determined as identifying leading themes through literature research and presenting a method proposal by grouping conceptually related themes. The unique value of the study is important in that the model to be created offers a potential to affect mass production tools, offices and local governments by incorporating contemporary architectural heritage products into a modeling process that can produce more innovative and faster solutions. The findings of the study show that the different techniques used can respond to different detail scales and different contextual challenges. Each modeling method and strategy creates different feedback mechanisms, mediating the recognition of the architectural heritage element by larger user groups or the more effective protection of the architectural heritage element. In the model presented as a result of the study, which mediates the gathering of the techniques used in different sample projects on a common working ground with a series of successive strategies, a comprehensive basis for which 3D printing solution will be used for which problem is presented and solution suggestions are offered for a case-oriented 3D printing strategy.

High-Performance low-k Poly(dicyclopentadiene)-POSS nanocomposites achieved by frontal polymerization

Low dielectric constant (low-k, k < 2.5) thermoset polymers play a crucial role in high-frequency communication technology and the microelectronic industry. However, existing low-k materials often suffer from time- and energy-consuming preparation procedures and have k values greater than 2.5. Herein, we present the frontal ring opening metathesis polymerization (FROMP) of dicyclopentadiene and phenyl-functionalized POSS bearing three and four norbornene groups (i.e., T7N3 and T8N4), enabling the rapid formation of high-performance low-k nanocomposites through a low energy consumption approach. The results reveal that T7N3 and T8N4 exhibit excellent compatibility with poly(dicyclopentadiene) (PDCPD) without adversely affecting the materials’ FROMP behaviors. Consequently, by increasing IC-POSS content, both the dielectric and comprehensive properties of PDCPD can be significantly enhanced while the influence of IC-POSS type remains limited. In particular, both PT7-40 (40 wt% of T7N3, k = 2.1) and PT8-40 (40 wt% of T8N4, k = 2.12) demonstrate the lowest k values; moreover, PT8-40 exhibits the highest dimensional stability (with a coefficient of thermal expansion of 79.3 ppm oC−1), glass transition temperature (188 °C), elastic modulus (2.32 GPa), yield strength (70.4 MPa), and hydrophobicity among all samples. By programming the front velocity, these materials can be processed into complex structures through a combination of FROMP and three-dimensional printing techniques. This work offers a facile and energy-efficient approach for preparing low-k materials with on-demand structures and properties.

3D Printing of Flexible BaTiO3/Polydimethylsiloxane Piezocomposite with Aligned Particles for Enhanced Energy Harvesting.

With the rapid development of human-machine interactions and artificial intelligence, the demand for wearable electronic devices is increasing uncontrollably all over the world; however, an unsustainable power supply for such sensors continues to restrict their applications. In the present work, piezoelectric barium titanate (BaTiO3) ceramic powder with excellent properties was prepared from milled precursors through a solid-state reaction. To fabricate a flexible device, the as-prepared BaTiO3 powder was mixed with polydimethylsiloxane (PDMS) polymer. The BaTiO3/PDMS ink with excellent rheological properties was extruded smoothly by direct ink writing technology (DIW). BaTiO3 particles were aligned due to the shear stress effect during the printing process. Subsequently, the as-printed composite was assembled into a sandwich-type device for effective energy harvesting. It was observed that the maximum output voltage and current of this device reached 68 V and 720 nA, respectively, for a BaTiO3 content of 6 vol %. Therefore, the material extrusion-based three-dimensional (3D) printing technique can be used to prepare flexible piezoelectric composites for efficient energy harvesting.

Magnetically driven formation of 3D freestanding soft bioscaffolds.

3D soft bioscaffolds have great promise in tissue engineering, biohybrid robotics, and organ-on-a-chip engineering applications. Though emerging three-dimensional (3D) printing techniques offer versatility for assembling soft biomaterials, challenges persist in overcoming the deformation or collapse of delicate 3D structures during fabrication, especially for overhanging or thin features. This study introduces a magnet-assisted fabrication strategy that uses a magnetic field to trigger shape morphing and provide remote temporary support, enabling the straightforward creation of soft bioscaffolds with overhangs and thin-walled structures in 3D. We demonstrate the versatility and effectiveness of our strategy through the fabrication of bioscaffolds that replicate the complex 3D topology of branching vascular systems. Furthermore, we engineered hydrogel-based bioscaffolds to support biohybrid soft actuators capable of walking motion triggered by cardiomyocytes. This approach opens new possibilities for shaping hydrogel materials into complex 3D morphologies, which will further empower a broad range of biomedical applications.

Three-dimensional printing technique aids screw insertion into the sustentaculum tali of the internal fixation of intra-articular calcaneal fractures

IntroductionTreating complex calcaneus fractures remains challenging. This study evaluated the influence of 3D printing and simulation on precision screw insertion into the calcaneus sustentaculum tali (ST). Hypothesis3D printing and simulation improve the treatment for calcaneal fracture. Patients and methodsThis retrospective cohort study included 85 patients admitted with 93 Sanders type II–IV intra-articular fractures from January 2015 to June 2020. Multi-slice computed tomography (MSCT) images were used in the conventional group, and MSCT data were used to construct a 3D model of the calcaneus to simulate screw insertion and verify parameter accuracy in the 3D group. ResultsThe designed parameters (upward and backward oblique angles and screw-path length) were similar to the actual values in the 3D group (p=0.428,0.287,0.585) but not in the conventional group (p=0.01,0.002,0.023). The Maryland foot functional score, accuracy rate, and average screw number were higher and operative time was shorter in the 3D group (p=0.005,0.007,0.000,0.000). DiscussionPreoperative simulation using the 3D printing model helped guide the screws into the ST more accurately, lending better-quality treatment for Sanders type II–IV calcaneal fractures. Level of proofIII; Retrospective case-control study.

Three-dimensionally printable hollow silica nanoparticles for subambient passive cooling

Abstract Solar reflectance and thermal emissivity are critical benchmarks for evaluating the effectiveness of passive cooling strategies. The integration of three-dimensional (3D) printing techniques with passive cooling materials enables local thermal management of multifaceted objects, offering opportunities for unexplored energy-saving applications. For example, conformal printing of cooling materials can mitigate solar absorption caused by the top metal electrodes in solar cells, thereby improving their efficiency and lifetime. In this study, we report the synthesis of 3D printable hollow silica nanoparticles (HSNPs) designed to induce subambient cooling performance under daylight conditions. HSNPs with diameters of 400–700 nm and silica shell thicknesses of approximately 100 nm were synthesized using an in-situ sol–gel emulsion method. Subsequently, these HSNPs were formulated into printable pastes by carefully selecting the mixture concentration and molecular weight of polyvinylpyrrolidone (PVP). The PVP-linked HSNPs exhibited a solar (0.3–2.5 μm) reflectivity of 0.98 and a thermal (8–13 μm) emissivity of 0.93. In contrast to a single silica nanoparticle (NP), the scattering analysis of a single HSNP revealed a distinctive scattering distribution characterized by amplified backward scattering and suppressed forward scattering. In outdoor daytime experiments, the HSNP-printed sample led to the subambient cooling of a dielectric substrate, surpassing the cooling performance of reference materials such as silica NPs, silver pastes, and commercial white plastics and paints.

Soft modularized robotic arm for safe human–robot interaction based on visual and proprioceptive feedback

This study proposes a modularized soft robotic arm with integrated sensing of human touches for physical human–robot interactions. The proposed robotic arm is constructed by connecting multiple soft manipulator modules, each of which consists of three bellow-type soft actuators, pneumatic valves, and an on-board sensing and control circuit. By employing stereolithography three-dimensional (3D) printing technique, the bellow actuator is capable of incorporating embedded organogel channels in the thin wall of its body that are used for detecting human touches. The organogel thus serves as a soft interface for recognizing the intentions of the human operators, enabling the robot to interact with them while generating desired motions of the manipulator. In addition to the touch sensors, each manipulator module has compact, soft string sensors for detecting the displacements of the bellow actuators. When combined with an inertial measurement unit (IMU), the manipulator module has a capability of estimating its own pose or orientation internally. We also propose a localization method that allows us to estimate the location of the manipulator module and to acquire the 3D information of the target point in an uncontrolled environment. The proposed method uses only a single depth camera combined with a deep learning model and is thus much simpler than those of conventional motion capture systems that usually require multiple cameras in a controlled environment. Using the feedback information from the internal sensors and camera, we implemented closed-loop control algorithms to carry out tasks of reaching and grasping objects. The manipulator module shows structural robustness and the performance reliability over 5,000 cycles of repeated actuation. It shows a steady-state error and a standard deviation of 0.8 mm and 0.3 mm, respectively, using the proposed localization method and the string sensor data. We demonstrate an application example of human–robot interaction that uses human touches as triggers to pick up and manipulate target objects. The proposed soft robotic arm can be easily installed in a variety of human workspaces, since it has the ability to interact safely with humans, eliminating the need for strict control of the environments for visual perception. We believe that the proposed system has the potential to integrate soft robots into our daily lives.

An Approach to 3D Printing Techniques, Polymer Materials, and Their Applications in the Production of Drug Delivery Systems

Three-dimensional printing (3DP) technologies are characterized as a set of innovative manufacturing techniques that allow for the creation of complex and/or personalized three-dimensional physical objects on the work surface of a 3D printing machine (based on the computer-aided design (CAD) project designs of these parts). Three-dimensional printing techniques are widely used in various areas of knowledge, such as education, engineering, and biomedicine. Polymeric materials are widely used for these applications, mainly due to their desirable workability during part manufacturing, compatibility with other chemical materials, the wide range of polymers with different physical and chemical characteristics, and the possibility for recycling. The development of polymeric drug delivery systems (DDSs) by 3D printing is currently an active field of research, both in academia and industry, given the potential of this technique for medical purposes. In this context, this work reviews potential polymers for the production of drug delivery systems via 3D printing techniques. The demonstrations of the main 3DP techniques used for drug delivery applications include their working principles and advantages and how the technologies develop the final product. In addition, potential synthetic and natural polymers that are currently used in 3DP drug delivery devices are presented and discussed based on recent scientific studies.

Bio-functional hydroxyapatite-coated 3D porous polyetherketoneketone scaffold for enhanced osteogenesis and osteointegration in orthopedic applications.

Polyetherketoneketone (PEKK), a high-performance thermoplastic special engineering material, maintains bone-like mechanical properties and has received considerable attention in the biomedical field. The 3D printing technique enables the production of porous scaffolds with a honeycomb structure featuring precisely controlled pore size, porosity and interconnectivity, which holds significant potential for applications in tissue engineering. The ideal pore architecture of porous PEKK scaffolds has yet to be elucidated. Porous PEKK scaffolds with five pore sizes P200 (225 ± 9.8 μm), P400 (411 ± 22.1 μm), P600 (596 ± 23.4 μm), P800 (786 ± 24.2 μm) and P1000 (993 ± 26.0 μm) were produced by a 3D printer. Subsequently, the optimum pore size, the P600, for mechanical properties and osteogenesis was selected based on in vitro experiments. To improve the interfacial bioactivity of porous PEKK scaffolds, hydroxyapatite (HAp) crystals were generated via in situ biomimetic mineralization induced by the phase-transited lysozyme coating. Herein, a micro/nanostructured surface showing HAp crystals on PEKK scaffold was developed. In vitro and in vivo experiments confirmed that the porous PEKK-HAp scaffolds exhibited highly interconnected pores and functional surface structures that were favorable for biocompatibility and osteoinductivity, which boosted bone regeneration. Therefore, this work not only demonstrates that the pore structure of the P600 scaffold is suitable for PEKK orthopedic implants but also sheds light on a synergistic approach involving 3D printing and biomimetic mineralization, which has the potential to yield customized 3D PEKK-HAp scaffolds with enhanced osteoinductivity and osteogenesis, offering a promising strategy for bone tissue engineering.

3D printing in biomedicine: advancing personalized care through additive manufacturing

The integration of three-dimensional (3D) printing techniques into the domains of biomedical research and personalized medicine highlights the evolving paradigm shifts within contemporary healthcare. This technological advancement signifies potential breakthroughs in patient-specific therapeutic interventions and innovations. This systematic review offers a critical assessment of the existing literature, elucidating the present status, inherent challenges, and prospective avenues of 3D printing in augmenting biomedical applications and formulating tailored medical strategies. Based on an exhaustive literature analysis comprising empirical studies, case studies, and extensive reviews from the past decade, pivotal sectors including tissue engineering, prosthetic development, drug delivery systems, and customized medical apparatuses are delineated. The advent of 3D printing provides precision in the fabrication of patient-centric implants, bio-structures, and devices, thereby mitigating associated risks. Concurrently, it facilitates the ideation of individualized drug delivery paradigms to optimize therapeutic outcomes. Notwithstanding these advancements, issues concerning material biocompatibility, regulatory compliance, and the economic implications of avant-garde printing techniques persist. To fully harness the transformative potential of 3D printing in healthcare, collaborative endeavors amongst academicians, clinicians, industrial entities, and regulatory bodies are paramount. With continued research and innovation, 3D printing is poised to redefine the trajectories of biomedical science and patient-centric care. The paper aims to justify the research objective of whether to what extent the integration of 3D printing technology in biomedicine enhances patient-specific treatment and contributes to improved healthcare outcomes.

Modularized microrobot with lock-and-detachable modules for targeted cell delivery in bile duct

The magnetic microrobots promise benefits in minimally invasive cell-based therapy. However, they generally suffer from an inevitable compromise between their magnetic responsiveness and biomedical functions. Herein, we report a modularized microrobot consisting of magnetic actuation (MA) and cell scaffold (CS) modules. The MA module with strong magnetism and pH-responsive deformability and the CS module with cell loading-release capabilities were fabricated by three-dimensional printing technique. Subsequently, assembly of modules was performed by designing a shaft-hole structure and customizing their relative dimensions, which enabled magnetic navigation in complex environments, while not deteriorating the cellular functionalities. On-demand disassembly at targeted lesion was then realized to facilitate CS module delivery and retrieval of the MA module. Furthermore, the feasibility of proposed system was validated in an in vivo rabbit bile duct. Therefore, this work presents a modular design–based strategy that enables uncompromised fabrication of multifunctional microrobots and stimulates their development for future cell-based therapy.

Realizing in-house algorithm-driven free fibula flap set up within 24 hours: a pilot study evaluating accuracy with open-source tools.

This study aims to critically evaluate the effectiveness and accuracy of a time safing and cost-efficient open-source algorithm for in-house planning of mandibular reconstructions using the free osteocutaneous fibula graft. The evaluation focuses on quantifying anatomical accuracy and assessing the impact on ischemia time. A pilot study was conducted, including patients who underwent in-house planned computer-aided design and manufacturing (CAD/CAM) of free fibula flaps between 2021 and 2023. Out of all patient cases, we included all with postoperative 3D imaging in the study. The study utilized open-source software tools for the planning step, and three-dimensional (3D) printing techniques. The Hausdorff distance and Dice coefficient metrics were used to evaluate the accuracy of the planning procedure. The study assessed eight patients (five males and three females, mean age 61.75 ± 3.69 years) with different diagnoses such as osteoradionecrosis and oral squamous cell carcinoma. The average ischemia time was 68.38 ± 27.95 min. For the evaluation of preoperative planning vs. the postoperative outcome, the mean Hausdorff Distance was 1.22 ± 0.40. The Dice Coefficients yielded a mean of 0.77 ± 0.07, suggesting a satisfactory concordance between the planned and postoperative states. Dice Coefficient and Hausdorff Distance revealed significant correlations with ischemia time (Spearman's rho = -0.810, p = 0.015 and Spearman's rho = 0.762, p = 0.028, respectively). Linear regression models adjusting for disease type further substantiated these findings. The in-house planning algorithm not only achieved high anatomical accuracy, as reflected by the Dice Coefficients and Hausdorff Distance metrics, but this accuracy also exhibited a significant correlation with reduced ischemia time. This underlines the critical role of meticulous planning in surgical outcomes. Additionally, the algorithm's open-source nature renders it cost-efficient, easy to learn, and broadly applicable, offering promising avenues for enhancing both healthcare affordability and accessibility.

Surface Modification of Polylactic Acid Bioscaffold Fabricated via 3D Printing for Craniofacial Bone Tissue Engineering.

Bone tissue engineering is a promising solution for advanced bone defect reconstruction after severe trauma. In bone tissue engineering, scaffolds in three-dimensional (3D) structures are crucial components for cell growth, migration, and infiltration. The three-dimensional printing technique is well suited to manufacturing scaffolds since it can fabricate scaffolds with highly complex designs under good internal structural control. In the current study, the 3D printing technique was utilized to produce polylactic acid (PLA) scaffolds. BMSCs were seeded onto selected scaffolds, either hydrogel-mixed or not, and cultivated in vitro to investigate the osteogenic potential in each group. After osteogenic incubation in vitro, BMSC-seeded scaffolds were implanted onto rat cranium defects, and bone regeneration was observed after 12 weeks. Our results demonstrated that BMSCs were able to seed onto 3D-printed PLA scaffolds under high-resolution observation. Real-time PCR analysis showed their osteogenic ability, which could be further improved after BMSCs were mixed with hydrogel. The in vivo study showed significantly increased bone regeneration when rats' cranium defects were implanted with a hydrogel-mixed BMSC-seeded scaffold compared to the control and those without cell or hydrogel groups. This study showed that 3D-printed PLA scaffolds are a feasible option for BMSC cultivation and osteogenic differentiation. After mixing with hydrogel, BMSC-seeded 3D-printed scaffolds can facilitate bone regeneration.

Epoxy (Meth)acrylate-Based Thermally and UV Initiated Curable Coating Systems.

Recently, photocurable coatings are being used frequently. However, it is worth mentioning that the use of photopolymerization has its drawbacks, especially in the case of curing coatings on three-dimensional surfaces and in places that are difficult to access for UV radiation. However, it is possible to develop a system in which UV technology and thermal methods for curing coatings can be combined. Moreover, the obtained resins are derived from low-viscosity epoxy resins or diglycidyl ethers, making them an ideal building material for photopolymerization-based three-dimensional printing techniques. Due to the need to improve this method, a series of epoxy (meth)acrylates containing both epoxy and (meth)acrylate groups were obtained via the addition of acrylic or methacrylic acid to epoxy resin, diglycydylether of bisphenol A epoxy resin (DGEBA), cyclohexane dimethanol diglycidyl ether (CHDMDE) and neopentyl glycol diglycidyl ether (NPDE). The structures of the synthesized copolymers were confirmed through spectroscopic analysis (FTIR) and studied regarding their nonvolatile matter content (NV) and acid values (PAVs), as well as their epoxy equivalent values (EEs). Due to the presence of both epoxy and double carbon-carbon pendant groups, two distinct mechanisms can be applied: cationic and radical. Hence, the obtained resins can be cured using UV radiation with thermally appropriate conditions and initiators. This type of method can be used as a solution to many problems currently encountered in using UV technology, such as failure to cure coatings in underexposed areas as well as deformation of coatings. Synthesized epoxy (meth)acrylate prepolymers were employed to formulate photocurable coating compositions. Furthermore, the curing process and properties of cured coatings were investigated regarding some structural factors and parameters. Among the synthesized materials, the most promising are those based on epoxy resin, characterized by their high glass transition temperature values and satisfactory functional properties.