Search Results (798)

Background: The fabrication of orthodontic aligners directly via three-dimensional (3D) printing presents potential to increase the efficiency of aligner production relative to traditional workflows; however, several aspects of the 3D printing process might affect the dimensional fidelity of the fabricated appliances. The aim of this study is to measure the forces expressed by a 3D printed aligner made with TC-85 DAC resin (Grapy Inc., Seoul, Republic of Korea) when an expansion movement of the entire upper dental arch is programmed, comparing the measured forces with those obtained by a common thermoformed aligner (Smart Track^®, Align Technology, Santa Clara, CA, USA). Materials and methods: A patient in transitional mixed dentition was selected, with the presence of all the first molars and permanent upper and lower incisors, and the canines and premolars have not started the exchange. From this patient, a virtual set up of the upper arch has been planned with an expansion of 0.2 mm and 0.4 mm per side; 3 mm horizontal rectangular attachments were added to the set up on the vestibular surface of the permanent molars, deciduous premolars, and deciduous canines. On this set up, 10 Smart Track aligners and 10 3D printed aligners with TC-85 DAC resin were produced. The fabricated aligners were mounted on the machinery used for the test (ElectroForce^® Test Bench; TA Instruments, New Castle, DE, USA) by means of specific supports that simulate the upper arch of the patient (divided into two sides: right and left). To simulate the intraoral environment, the measurements were carried out in a thermostatic bath at a temperature of 37 °C. Results: The key results of this paper showed differences between Smart Track^® and TC-85 DAC. In particular, the expanding force exerted by the 0.2 mm per side expanded Smart Track^® aligners was on average +0.2162 N with a D.S. of ±0.0051 N during the 8 h; meanwhile, the force exerted by the 0.2 mm per side expanded TC-85 DAC 3D printed aligners was on average −0.0034 N with a D.S. of ±0.0036 N during the 8 h. The force exerted by the 0.4 mm per side expanded Smart Track^® aligners was on average +0.7159 N with a D.S. of ±0.0543 N during the 8 h; meanwhile, the force exerted by the 0.4 mm per side expanded TC-85 DAC 3D printed aligners was on average +0.0141 N with a D.S. of ±0.004 N during the 8 h. Conclusions: Smart Track^® aligners express a quantitatively measurable force in Newtons during the programmed movements to obtain a posterior expansion of the dental arches; on the contrary, aligners made with TC-85 DAC resin, in light of the results obtained from this study, express forces close to 0 during the realization of the movements programmed to obtain a posterior expansion of the dental arches. Full article

This study investigates the processability—via Fused Deposition Modeling (FDM) 3D printing—and mechanical performance of biocomposites based on polylactic acid (PLA), polybutylene succinate (PBS), and their 50/50 wt% blend, each reinforced with hemp shive at 3 and 5 wt%. Blending PLA with PBS represents a straightforward and encouraging strategy to enhance both the printability and mechanical properties of the individual resins, expanding the range of their potential applications. The addition of hemp shive—a by-product of hemp processing—not only enhances the biodegradability of the composites but also improves their thermo-mechanical performance, as well as aligning with circular economy principles. The rheological characterization, performed on all the systems, evidenced that the PLA/PBS blend possesses viscoelastic properties well suited for FDM, enabling smooth extrusion through the nozzle, good shape stability after deposition, and effective interlayer adhesion. Moreover, the constrain effect of hemp shives within the polymer matrix reduced the extrudate swell, a key factor affecting the dimensional accuracy of the printed parts. Optimal processing conditions were identified at a nozzle temperature of 190 °C and a printing speed of 70 mm/s, providing a favorable compromise between print quality, final performances and production efficiency. From a mechanical perspective, the PLA/PBS blend exhibited an 8.6-fold increase in elongation at break compared to neat PLA, and its corresponding composite showed a ductility nearly three times higher than the PLA-based counterpart’s. In conclusion, the findings of this study provide new insights into the interplay between material formulation, rheological behavior and printing conditions, supporting the development of sustainable, hemp-reinforced biocomposites for additive manufacturing applications. Full article

The transition from three-dimensional (3D) to four-dimensional (4D)-bioprinting marks a significant advancement in tissue engineering and drug delivery. 4D-bioprinting offers the potential to more accurately mimic the adaptive qualities of living tissues due to its dynamic flexibility. Structures created with 4D-bioprinting can change shape in response to internal and external stimuli. This article reviews the background, key concepts, techniques, and applications of 4D-bioprinting, focusing on its role in tissue scaffolding and drug delivery. We discuss the limitations of traditional 3D-bioprinting in providing customized and sustained medication release. Shape memory polymers and hydrogels are examples of new responsive materials enabled by 4D-bioprinting that can enhance drug administration. Additionally, we provide a thorough analysis of various biopolymers used in drug delivery systems, including cellulose, collagen, alginate, and chitosan. The use of biopolymers in 4D-printing significantly increases material responsiveness, allowing them to react to stimuli such as temperature, light, and humidity. This capability enables complex designs with programmable shape and function changes. The expansion and contraction of hydrogels in response to temperature changes offer a practical method for controlled drug release. 4D-bioprinting has the potential to address significant challenges in tissue regeneration and medication administration, spurring ongoing research in this technology. By providing precise control over cell positioning and biomaterial integration, traditional 3D-bioprinting has evolved into 4D-bioprinting, enhancing the development of tissue constructs. 4D-bioprinting represents a paradigm shift in tissue engineering and biomaterials, offering enhanced possibilities for creating responsive, adaptive structures that address clinical needs. Researchers can leverage the unique properties of biopolymers within the 4D-printing framework to develop innovative approaches for tissue regeneration and drug delivery, leading to advanced treatments in regenerative medicine. One potential future application is in vivo tissue regeneration using bioprinted structures that can enhance the body’s natural healing capabilities. Full article

Three-dimensional concrete printing (3DCP) is an emerging additive manufacturing technology with increasing application potential in the construction industry, offering advantages such as reduced labor requirements, shortened construction time, and material efficiency. However, structural integrity remains a challenge, particularly due to weak interlayer bonding resulting from the layered manufacturing process. This study investigates the mechanical performance and anisotropy of 3D-printed mineral-based composites with respect to the time interval between successive layers. Specimens were printed with varying interlayer intervals (0, 25, and 50 min) and tested in different loading directions. Flexural, compressive, and tensile strengths (direct and splitting methods) were measured both parallel and perpendicular to the layer orientation. Results showed a clear degradation in mechanical properties with increasing interlayer time, particularly in the direction perpendicular to the layers. Flexural strength decreased by over 25% and direct tensile strength by up to 40% with a 25 min interval. Compressive strength also declined, though less dramatically. Compared to cast specimens, printed elements showed 3–4 times lower compressive strength, highlighting the significant impact of interlayer cohesion. This study confirms that both the time between layers and the loading direction strongly influence mechanical behavior, underlining the anisotropic nature of 3DCP elements and the need for process optimization to ensure structural reliability. Full article

This study explores the self-healing properties of polyurethane nanocomposites enhanced by multiple hydrogen bonds from ureido-pyrimidinone and the incorporation of 1–3 wt.% graphene nanoparticles, based on polyol α,ω-dihydroxy[oligo(butylene-ethylene adipate)]diol, which, according to our knowledge, has not been previously used in such systems. These new materials were synthesized via a two-step process and characterized by their thermal, mechanical, chemical, and self-healing properties. The mechanical analysis revealed that all nanocomposites exhibited high self-healing efficiencies (88–91%). The PU containing 2% graphene stands out as it exhibits the highest initial mechanical strength of ~5 MPa compared to approximately 2MP for a pristine PU while maintaining excellent self-healing efficiency (88%). A cut on the PU nanocomposite with 2% graphene can be completely healed after being heated at 80 °C for 1 h, which shows that it has a fast recovery time. Moreover, 3D printing was also successfully used to assess their processability and its effect on self-healing behavior. Three-dimensional printing did not negatively affect the material regeneration properties; thus, the material can be used in a variety of applications as expected in terms of dimensions and geometry. Full article

Mycelium is a living material that has gained popularity over the last decade in both architecture and design. Apart from understanding the physical behaviour of novel materials, it is also important to grasp how designers and the general audience perceive them. On the one hand, this study investigated mycelium growth in 3D-printed minimal surface shapes using a wood-based filament, and on the other hand, it examined how both designers and the general public experience interacting with mycelium. Using a material-driven design research method, a workshop with architecture students was conducted where various triply periodic minimal surfaces were designed and 3D printed. These shapes were used as molds and impregnated with mycelium, and the growth of mycelium was analyzed visually and photographically. Data on the experiences of the 30 workshop participants of working with mycelium was collected through a survey and analyzed qualitatively. After exhibiting results of the workshop in a public-facing exhibition, semi-structured interviews with members of the general public about their perceptions of mycelium were conducted. Three-dimensionally printed minimal surfaces with wood-based filaments can function as structural cores for mycelium-based composites, and the density of the minimal surface appears to influence mycelium growth, which binds to wood-based filaments. Students exhibited stronger feelings for living materials compared to non-living ones, displaying both biophilia and, to a lesser extent, biophobia. Introducing hands-on workshops with living and experimental materials in design studio settings can help future generations of designers develop sensibilities for, and a critical approach towards, the impact of their design decisions on the environment and sustainability. The study also contributes empirical data on how members of the general public perceive mycelium as a material for design. Full article

Additive manufacturing (AM) has emerged as a transformative technology in dentistry, enabling the production of patient-specific dental applications with reduced costs and fabrication times. Despite the growth of applications, a consolidated understanding of current 3D printing technologies, materials, and performance in dental settings remains fragmented. Here, we perform a Systematic Literature Review (SLR) using the PRISMA protocol, retrieving 19 closely related primary studies. The evidence is synthesized across three axes: application domain, AM technology, and critical quality parameters. Dental restorations, prosthetics, crowns, and implants are the most common applications, while fused deposition modeling, stereolithography, digital light processing, selective laser sintering, and laser-directed energy deposition are the most used technologies. AM materials include polymers, metals, and emerging biomaterials. Key quality determinants include dimensional accuracy, wear and corrosion resistance, and photosensitivity. Notably, biocompatibility and cytotoxicity remain underexplored yet critical factors for ensuring long-term clinical safety. The evidence also suggests a lack of in vivo studies, insufficient tribological and microbiological testing, including limited data degradation pathways of AM materials under oral conditions. Understanding that there are disconnects between the realization of the clinical and the economic benefits of 3D printing in dentistry, future research requires standardized testing frameworks and long-term biocompatibility validation. Full article

The accordion honeycomb has unique deformation characteristics in cellular materials. This study develops a three-dimensional equivalent Cauchy continuum model (3D-ECM) based on the variational asymptotic method (VAM) to efficiently predict the mechanical response of the accordion honeycomb. The accuracy of the 3D-ECM is validated via quasi-static compression experiments on 3D-printed specimens and detailed 3D finite element simulations (3D-FEM), showing a strong correlation between simulation and experimental data. Parametric analyses reveal that the re-entrant angle, ligament-to-strut length ratio, and thickness ratios significantly affect the equivalent elastic moduli, providing insights into geometric optimization strategies for targeted mechanical performance. Comparative experiments among honeycomb structures with positive, negative, and zero Poisson’s ratios show that the accordion honeycomb achieves superior dimensional stability and tunable stiffness but exhibits lower energy-absorption efficiency due to discontinuous buckling and recovery processes. Further comparison among different ZPR honeycombs confirms that the accordion design offers the highest equivalent modulus in the re-entrant direction. The findings underscore the accordion honeycomb’s promise in scenarios demanding structural reliability, tunable stiffness, and moderate energy absorption. Full article

Hydrogen is widely recognized as a key enabler of the clean energy transition, but the lack of safe, efficient, and scalable storage technologies continues to hinder its broad deployment. Conventional hydrogen storage approaches, such as compressed hydrogen storage, cryo-compressed hydrogen storage, and liquid hydrogen storage, face limitations, including high energy consumption, elevated cost, weight, and safety concerns. In contrast, solid-state hydrogen storage using carbon-based adsorbents has gained growing attention due to their chemical tunability, low cost, and potential for modular integration into energy systems. This review provides a comprehensive evaluation of hydrogen storage using carbon-based materials, covering fundamental adsorption mechanisms, classical materials, emerging architectures, and recent advances in computationally AI-guided material design. We first discuss the physicochemical principles driving hydrogen physisorption, chemisorption, Kubas interaction, and spillover effects on carbon surfaces. Classical adsorbents, such as activated carbon, carbon nanotubes, graphene, carbon dots, and biochar, are evaluated in terms of pore structure, dopant effects, and uptake capacity. The review then highlights recent progress in advanced carbon architectures, such as MXenes, three-dimensional architectures, and 3D-printed carbon platforms, with emphasis on their gravimetric and volumetric performance under practical conditions. Importantly, this review introduces a forward-looking perspective on the application of artificial intelligence and machine learning tools for data-driven sorbent design. These methods enable high-throughput screening of materials, prediction of performance metrics, and identification of structure–property relationships. By combining experimental insights with computational advances, carbon-based hydrogen storage platforms are expected to play a pivotal role in the next generation of energy storage systems. The paper concludes with a discussion on remaining challenges, utilization scenarios, and the need for interdisciplinary efforts to realize practical applications. Full article

Background: Accuracy of optical impressions—defined by the intraoral scanner (IOS)’s trueness and precision per International Organization for Standardization (ISO) standards—is influenced by both operator- and patient-related factors. Thus, this in vitro study aimed to (1) evaluate how scanning distance affects the accuracy of three different intraoral scanners (IOSs), and (2) identify the optimal scanning distance for each scanner. Methods: A maxillary arch model was obtained using polyvinyl siloxane impression material and poured with Type IV stone (Octa-rock royal^®, Kulzer, Germany). Using three different types of IOSs—the trios 3 shape (TRIOS ^® cart, 3Shape, Copenhagen, Denmark); the Helios 500 (Eighteeth ^®, Changzhou, China); and the Heron (3Disc ^®, Herndon, VA 20170, USA)—ten scans were performed with each of the IOSs with five predetermined distances: 0 mm, 2.5 mm, 5 mm, 7.5 mm, and 10 mm. Spacers of varying heights were designed using Meshmixer version 3.5 (Autodesk, Inc., Mill Valley, CA, USA) and three-dimensional printed with the Form 2 printer (Formlabs, Somerville, MA, USA). The scanned data was processed using Geomagic Control X (Version 16.0.2.16496, 3D Systems, Wilsonville, OR, USA). Statistical analyses were performed using R Statistical Software (version 4.2.2), with significance set at α = 0.05. Results: Scanning distance significantly influenced scan accuracy for all three scanners. The 3Disc scanner (3Disc, Herndon, VA, USA) demonstrated the highest accuracy at a 7.5 mm distance, while both the Helios 500 (Eighteeth, Changzhou, China) and Trios 3 (3Shape, Copenhagen, Denmark) scanners achieved their best accuracy at a 5 mm distance, as indicated by the lowest root mean square (RMS) values (p < 0.05). Conclusions: To conclude, each IOS has an optimal scanning distance for best accuracy. Trios 3 (3Shape, Copenhagen, Denmark) outperformed the others in both trueness and precision. Future studies should examine these effects under full-arch and clinical conditions. Full article

Sophisticated energy-harvesting technologies have swiftly progressed, expanding energy supply distribution and leveraging advancements in self-sustaining electronic devices. Despite substantial advancements in friction nanomotors within the last decade, a considerable technical obstacle remains for their flawless incorporation using printed electronics and autonomous devices. Integrating advanced triboelectric nanogenerator (TENG) technology with the rapidly evolving field of composite material 3D printing with has resulted in the advancement of three-dimensionally printed TENGs. Triboelectric nanogenerators are an important part of the next generation of portable energy harvesting and sensing devices that may be used for energy harvesting and artificial intelligence tasks. This paper systematically analyzes the continual development of 3D-printed TENGs and the integration of composite materials. The authors thoroughly review the latest material combinations of composite materials and 3D printing techniques for TENGs. Furthermore, this paper showcases the latest applications, such as using a TENG device to generate energy for electrical devices and harvesting energy from human motions, tactile sensors, and self-sustaining sensing gloves. This paper discusses the obstacles in constructing composite-material-based 3D-printed TENGs and the concerns linked to research and methods for improving electrical output performance. The paper finishes with an assessment of the issues associated with the evolution of 3D-printed TENGs, along with innovations and potential future directions in the dynamic realm of composite-material-based 3D-printed TENGs. Full article

The development of high-performance adsorbent materials is crucial for any sorption-based energy conversion process. In such a context, composite sorbent materials, although promising in terms of performance and stability, are often challenging to shape into complex geometries. Additive manufacturing, also known as 3D printing, has emerged as a powerful technique for fabricating intricate structures with tailored properties. In this paper, an innovative three-dimensional structure, constituted by zeolite as filler and sulfonated polyether ether ketone as matrix, was obtained using additive manufacturing technology, which is mainly suitable for sorption-based energy conversion processes. The lattice structure was tailored in order to optimize the synthesis procedure and material stability. The complex three-dimensional lattice structure was obtained without a metal or plastic reinforcement support. The composite structure was evaluated to assess its structural integrity using morphological analysis. Furthermore, the adsorption/desorption capacity was evaluated using water-vapor adsorption isobars at 11 mbar at equilibrium in the temperature range 30–120 °C, confirming good adsorption/desorption capacity. Full article

Three-dimensional (3D) concrete printing (3DCP) has gained significant attention over the last decade due to its many claimed benefits. The absence of effective real-time quality control mechanisms, however, can lead to inconsistencies in extrusion, compromising the integrity of 3D-printed structures. Although the importance of quality control in 3DCP is broadly acknowledged, research lacks systematic methods. This research investigates the feasibility of using ultrasonic pulse velocity (UPV) as a practical, in situ, real-time monitoring tool for 3DCP. Two different groups of binders were investigated: limestone calcined clay (LC³) and zeolite-based mixes in binary and ternary blends. Filaments of 200 mm were extruded every 5 min, and UPV, pocket hand vane, flow table, and viscometer tests were performed to measure pulse velocity, shear strength, relative deformation, yield stress, and plastic viscosity, respectively, in the fresh state. Once the filaments presented printing defects (e.g., filament tearing, filament width reduction), the tests were concluded, and the open time was recorded. Isothermal calorimetry tests were conducted to obtain the initial heat release and reactivity of the supplementary cementitious materials (SCMs). Results showed a strong correlation (R² = 0.93) between UPV and initial heat release, indicating that early hydration (ettringite formation) influenced UPV and determined printability across different mixes. No correlation was observed between the other tests and hydration kinetics. UPV demonstrated potential as a real-time monitoring tool, provided the mix-specific pulse velocity is established beforehand. Further research is needed to evaluate UPV performance during active printing when there is an active flow through the printer. Full article

The research presented in this paper focuses on the utilization of 3D printing technology in the design and manufacture of a prosthetic hand, equipped with a digit replicator. The subject of this study was a young man who had undergone the amputation of two fingers on his right hand. The electronic control of the movement of the finger copy was developed using Arduino language. A concept and outline drawings were developed in ProCreate. Three-dimensional scan of the hand and forearm was made using an EinScan PRO HD SHINING 3D scanner. Using CAD software—Autodesk Inventor and Autodesk Meshmixer, the prosthesis was designed. Printing was carried out on a 3D printer of the i3 MK3 and MK3+ series using a PLA (polylactic acid) filament. It was determined that PLA is an optimal material for printing, as it is considered to be safe for future patients’ skin. Work on the electronic circuitry started in Autodesk TinkerCad simulation software, allowing the code to be verified and ensuring the safety of the control system. The prosthesis’s design demonstrates the potential to reach as many people in need as possible by using readily available, low-cost, and easy-to-use components. Full article

Microneedle arrays (MNAs) are becoming increasingly popular due to their ease of use and effectiveness in drug delivery and diagnostic applications. Improvements in three-dimensional (3D) printing techniques have made it possible to fabricate MNAs with high precision, intricate designs, and customizable properties, expanding their potential in medical applications. While most studies have focused on transdermal applications, non-transdermal uses remain relatively underexplored. This review summarizes recent developments in 3D-printed MNAs intended for non-transdermal drug delivery and diagnostic purposes. It includes a literature review of studies published in the past ten years, organized by the target delivery site—such as the brain and central nervous system (CNS), oral cavity, eyes, gastrointestinal (GI) tract, and cardiovascular and reproductive systems, among other emerging areas. The findings show that 3D-printed MNAs are more adaptable than skin-based delivery, opening up exciting new possibilities for use in a variety of organs and systems. To guarantee the effective incorporation of polymeric non-transdermal MNAs into clinical practice, additional research is necessary to address current issues with materials, manufacturing processes, and regulatory approval. Full article