3D Printing Process Research Articles

Production of platelet-rich plasma (PRP)-enriched scaffolds for bone tissue regeneration with 3D printing technology

Bone disorders signify diverse abnormalities in the structure, development, and functions of bone tissue in the human body, with a significant correlation to ageing, insufficient physical activity, and escalating obesity. Recent advancements in bone tissue engineering aim to enhance bone tissue formation through the use of biomaterials, growth factors, and cells. The present study focuses on the fabrication and characterisation of scaffolds with a composition of gelatin (GEL) / sodium alginate (SA) / hydroxyapatite (HA) / platelet-rich plasma (PRP) using the 3D printing process. The inclusion of PRP, derived from blood, is of particular interest due to its potential to enhance bone regeneration through various growth factors. Scanning electron microscope (SEM) analysis revealed average pore sizes ranging from 481.50 ± 7.65 to 623.96 ± 11.54 µm. SEM images also showed that scaffold surfaces became smooth as the concentration of PRP increased. The mechanical test results demonstrated that as the PRP increased, the compressive strength decreased. When the swelling and degradation behaviours of scaffolds were examined, it was observed that GEL/SA/HA/3PRP scaffolds exhibited approximately 200 % swelling capability until the 4th day. GEL/SA/HA scaffolds showed a degradation behaviour about 70 % higher compared to other groups. A controlled release profile of PRP was maintained up to the 144th, 216th, and 240th hours from the scaffolds. According to the highest correlation coefficients (R2) in the release kinetics of scaffolds, GEL/SA/HA/0.5PRP and GEL/SA/HA/1PRP scaffolds were explained by the first-order model. In contrast, the GEL/SA/HA/3PRP scaffold was described using the Korsmeyer–Peppas model. The MTT analysis conducted with osteoblast cells showed that scaffolds did not demonstrate any toxic effects and facilitated cell adhesion by inducing the formation of extensions. These findings underscore the potential of PRP-incorporated GEL/SA/HA composites as a promising approach for bone tissue engineering, offering significant advancements in the treatment of bone disorders. This could lead to more effective treatments for bone disorders and injuries, reducing the need for more invasive procedures and improving patient recovery times.

Improving Additive Manufacturing for Housing Construction

The use of additive manufacturing in construction can significantly reduce the speed of construction of an object, labor costs, waste, reduce the risks of industrial injuries, etc. Despite a number of existing advantages of these technologies, their implementation in construction is associated with various problems, one of which is the need to ensure the required adhesion strength of printed layers. There are a number of studies devoted to solving this problem and creating effective materials for additive construction production, mainly based on cement binders; to a much lesser extent, these studies are available in the field of mixtures based on gypsum and mixed (gypsum-cement-pozzolanic) binders. The purpose of this work is to develop a scientifically based technological solution for improving additive technologies for low-rise housing construction using gypsum-cement-pozzolanic mixtures (GCPS) by regulating recipe-technological factors that provide increased adhesion strength of printed layers. Based on the results of the research, a technological solution has been developed to improve the technology of additive construction production of GCPM by regulating the kinetics of the increase in plastic strength of the mixture when it is modified with a multifunctional complex additive, which makes it possible to ensure the viability of the mixture required for 3D printing in the range of 0–50 minutes, significantly reduce the defectiveness of the extrudate during the 3D printing process, and increase the adhesion strength of the printed layers. It has been established that the adhesion strength of layers printed without a technological break from the GCP concrete mixture, modified with multifunctional complex additive, is 65% higher compared to the base composition, and when a technological break lasts 6 hours, it is 25% higher, which confirms its effectiveness in additive manufacturing.

Investigation of the humidity control in the printing space for the material extrusion of medical biodegradable hydrogel

Materials extrusion for medical biodegradable hydrogel manifests potential for the fabrication of biomimetic functionalized tissues in tissue engineering. However, the uncontrollable shape of 3D printed structures usually leads to shrinkage as well as collapse of the prepared biocompatible scaffold, which limits the potential to develop large-size tissue or organs. Uncontrollable ambient humidity during the 3D printing process is a primary cause of the moisture loss and geometric variation of prepared architectures, which means the humidity in the printing space of hydrogel materials must be controlled accurately throughout the extrusion process. This study proposed a novel configuration of humidity-controlled atmospheric enclosure, by which the humidity distribution in the printing space can be accurately regulated. Subsequently, a fluid-thermal-humidity coupling field simulation model based on the finite element method was established to numerically investigate the humidity field in the printing space. Furthermore, printing trials were conducted with the proposed atmospheric enclosure, and the moisture loss of 3D architecture was avoided. The size of the scaffold was improved evidently from 25 mm(length) × 25 mm(width) × 0.6 mm(height) to 25 mm(length) × 25 mm(width) × 3.5 mm(height).

Reproducing wrought grain structure in additive IN718 through nanosecond laser induced cavitation

Pulsed laser assisted additive manufacturing has been demonstrated as a promising technology for controlling grain structure in 3D-printing processes. The integration of a nanosecond laser onto a wire arc additive manufacturing tool has enabled the localized printing of Inconel 718 with grain sizes meeting ASTM 9 standards (average measured grain size of 13.7μm) for wrought material within a single bead under solidification conditions that would otherwise produce 340μm columnar grains. The observed grain refinement holds promise, provided scale up is possible, for overcoming the highly anisotropic mechanical properties and microcracking associated with large columnar grains of Inconel 718 that have long stood in the way of leveraging the advantages of direct energy deposition printing techniques of difficult to machine alloys. Experiments on large bead sizes allowed for decoupling surface versus bulk nanosecond laser/liquid metal interaction mechanisms to determine that the source of the observed grain refinement is the collapse of cavitation bubbles originating from acoustic waves generated by momentum transfer into the melt of an ablation plasma. Additionally, experiments that increased the cavitation bubble density within the mushy zone during solidification by tuning the nanosecond laser scan path went beyond the 25 times reduction in grain size to a 70 times factor of refinement with a minimum average grain diameter approaching 4μm.

Design of a Robotic 3D Printing System

Abstract Additive manufacturing enables the production of complex shapes with a large degree of freedom compared to conventional manufacturing techniques such as injection molding, thermoforming or pressing. In particular, the creation of moving parts, complex structures and large-scale printing remains underexplored and research is constantly expanding. Due to design limitations related to the construction of currently available printers, 3D printing technology is increasingly being combined with robotics. Using a robot to 3D print products eliminates the need to design complex printer structures, which ultimately should simplify the process of manufacturing large-scale products and shorten the time required for preparation and production. The paper deals with the description of the designed 3D printing system and the procedure of the steps of creating a robotic simulation model with the generation of a control program for the FDM 3D printing process by an industrial robot.

Influence of 3D printed porous aluminum anode structure on electrochemical performance

Aluminium-air (Al-air) batteries have been considered as one of the most promising next-generation energy storage devices. In this study, we investigated the effect of structural changes in the main body of porous aluminium anode on the electrochemical performance under the constraints of the 3D printing process using both simulation and experimental methods. By analysing the simulation results under the constraint of 3D printing process, we found that the variation of the base fillet radius affects the dimensional deviation of the porous aluminium anode. As the radius of the fillet increases, the degree of warpage deformation gradually decreases. For this reason, we experimentally verified the self-corrosion rate, electrochemical and discharge properties of aluminium anodes under the same process parameters. The test results are consistent with the simulation analysis. With the increase of fillet radius, the self-corrosion rate of anode gradually decreases and the electrochemical activity gradually increases. Meanwhile, the discharge voltage was as low as 1.55 V in the periphery without rounded corners, and increased by 1.3 % and 3.2 % when the periphery radius was 1 mm and 2 mm, respectively. This research result provides a new method for other researchers to further improve the overall performance of aluminium-air batteries.

Advances in 4D printing of biodegradable photopolymers

Advances in 4D printing of biodegradable photopolymers

Innovative Die Component Manufacturing by Using Lost Wax Casting and 3D Printing Processes

Abstract: The project focuses on crafting a casting die for designing the micro jet nozzle of an aircraft engine. The manufacturing of the casting die involves various steps outlined in the procedure. Regular stone material, categorized under ceramic parts, is utilized for constructing the casting die. The primary objective of this project is to integrate additive manufacturing into the production of automobile parts and the construction of mechanical components. We are going to fabricate d casting die by using different material other than regular casting material which is more accurate. This project involves 3Dprinting technology and SLA printing technologies.

Enhancing Clay-Based 3D-Printed Mortars with Polymeric Mesh Reinforcement Techniques.

Additive manufacturing (AM) technologies, including 3D mortar printing (3DMP), 3D concrete printing (3DCP), and Liquid Deposition Modeling (LDM), offer significant advantages in construction. They reduce project time, costs, and resource requirements while enabling free design possibilities and automating construction processes, thereby reducing workplace accidents. However, AM faces challenges in achieving superior mechanical performance compared to traditional methods due to poor interlayer bonding and material anisotropies. This study aims to enhance structural properties in AM constructions by embedding 3D-printed polymeric meshes in clay-based mortars. Clay-based materials are chosen for their environmental benefits. The study uses meshes with optimal geometry from the literature, printed with three widely used polymeric materials in 3D printing applications (PLA, ABS, and PETG). To reinforce the mechanical properties of the printed specimens, the meshes were strategically placed in the interlayer direction during the 3D printing process. The results show that the 3D-printed specimens with meshes have improved flexural strength, validating the successful integration of these reinforcements.

Application of 3D and 4D Printing in Electronics

Nowadays, additive manufacturing technologies have impacted different engineering sectors. Three- and four-dimensional printing techniques are increasingly used in soft and flexible electronics thanks to the possibility of working contemporarily with several materials on various substrates. The materials portfolio is wide, as well as printing processes. Shape memory polymers, together with composites, have gained great success in the electronic field and are becoming increasingly popular for fabricating pH, temperature, humidity, and stress sensors that are integrated into wearable, stretchable, and flexible devices, as well as for the fabrication of communication devices, such as antennas. Here, we report an overview of the state of the art about the application of 4D printing technologies and smart materials in electronics.

A review on cutting-edge innovations in dental implantology

Dental implantology has advanced significantly with innovations in materials, designs, surgical techniques, and digital technology aimed at enhancing patient outcomes. Applications span specialties like prosthodontics, periodontics, orthodontics, oral surgery, aesthetic dentistry, and pediatric dentistry, with pediatric implants showing a success rate of 90-95% over ten years. 4D printing is emerging as a transformative technology for dynamic implants. This review traces the historical development from ancient attempts to modern titanium-based designs, emphasizing milestones like osseo-integration discovery by Dr. Per-Ingvar Brånemark. Recent progress includes enhanced titanium surfaces, biocompatible zirconia, and composite materials, as well as innovations in implant design such as nanotechnology-enhanced surfaces and personalized implants, all aimed at improving osseointegration and stability, while surgical approaches now prioritize minimally invasive techniques, immediate loading protocols, and computer-guided procedures to minimize patient discomfort and expedite recovery was discussed.

Fluorescent Polylactic acid composite incorporating lignin-based carbon quantum dots for sustainable 4D printing applications

Fluorescent 4D printing materials, as innovative materials that combine fluorescent characteristics with 4D printing technology, have attracted widespread interest and research. In this study, green lignin-derived carbon quantum dots (CQDs) were used as the fluorescent module, and renewable poly(propylene carbonate) polyurethane (PPCU) was used for toughening. A new low-cost fluorescent polylactic acid (PLA) composite filament for 4D printing was developed using a simple melt extrusion method. The strength of the prepared composite was maintained at 32 MPa, while the elongation at break increased 8-fold (34 % increase), demonstrating excellent shape fixed ratio (∼99 %), recovery ratio (∼92 %), and rapid shape memory recovery speed. The presence of PPCU prevented fluorescence quenching of the CQDs in the PLA matrix, allowing the composite to emit bright green fluorescence under 365 nm ultraviolet light. The composite exhibited shear thinning behavior and had an ideal melt viscosity for 3D printing. The results obtained demonstrated the versatility of these easy-to-manufacture and low-cost filaments, opening up a novel and convenient method for the preparation of strong, tough, and multifunctional PLA materials, increasing their potential application value.

Sustainable 3D-printed cellulose-based biocomposites and bio-nano-composites: Analysis of dielectric performances

The development of cellulose-reinforced biomaterials appears to be an attractive approach for the production of sustainable materials with good mechanical properties. Although 3D printing of cellulose-reinforced biomaterials has become popular, there is very little feedback regarding their use in electrical insulation applications. This study aims to propose bio-nano-composites containing polylactic acid (PLA), microcrystalline (MCC) and nanocrystalline (NCC) cellulose by fused filament fabrication (FFF) for electrical insulation applications. The influence of the 3D printing process, cellulose content and filler size on dielectric properties was investigated. The addition of cellulosic fillers, and considering their high polarity, increased the dielectric constant (ε'), dielectric loss (ε''), as well as the AC electrical conductivity (σAC) of the composites. Cellulosic fillers also increased the crystallization rate of the materials. At equivalent content, the highest polarization potential were observed for NCC-based composites and were attributed to the nanofiller's better dispersion and available specific surface area. Finally, the 3D printing process affects all the measured properties, due to a combined effect (lower crystalline content and voids presence). The porosity rate was measured at 2.5 % for the neat PLA and increased progressively from 3.1 % to 5.8 % for the cellulose-based composites. These findings showed the benefits provided by the FFF technology in the production of cellulose-based biocomposites with good electrical insulation properties, while noting some needed feedback on the thermomechanical properties of such materials.

Lazy thermal annealing of material extrusion-based 3D-printed PLA specimens

AbstractMaterial extrusion (ME)-based 3D printing process is widely used nowadays, and the created parts can be used for rapid prototyping or as a finished part for industrial representatives, but the technology is also popular among home users. One of the greatest limitations of the parts created by ME is the mechanical anisotropy resulting from the extrusion process. The inter- and intra-layer adhesion makes the parts prone to early failure. By thermal post-processing, this kind of bond can be improved; however, that would need an investment of some new equipment/machines. In this article, a “lazy annealing” thermal post-processing method is presented, where the parts are cured on the 3D printer to increase their mechanical resistance. According to the results, even with this simple method, a significant increment can be achieved, but it has less effect on the infill patterns.

Novel 4D-printing pellets with infrared-light responsive shape memory effect

Four-dimensional (4D)-printing technology is attractive to researchers since it combines 3D printing with smart materials to produce 3D structures with various shapes and change shapes under specific external stimuli. Herein, novel shape memory polymer (SMP) pellets with infrared-light responsive shape memory effect were developed for 4D printing applications. The structures, properties, and infrared-light responsive shape memory performances of the resulting (SMP) pellets were thoroughly investigated. The results showed PDA/SMP pellets prepared by direct loading of polydopamine (PDA) particles on SMP pellets displayed less influence on the basic properties of SMP while fluidity was enhanced. The obtained PDA/SMP pellets employed as feed materials for particle 3D printers revealed good thermal-induced shape memory performance and photo-responsive shape memory performance in printed 3D structures. Under infrared-light irradiation, the curled shape recovered to straight splines within 60 s due to the strong absorption and good photo-thermal conversion of the loaded PDA nanoparticles under infrared light. Overall, the as-prepared PDA/SMP pellets look promising for use in biomedical fields and smart devices, as well as remote control deformation with 4D printing technology.

Mechanically sustainable and primary recycled thermo-responsive ABS–PLA polymer composites for 4D printing applications: Fabrication and studies

Abstract 3D printing is one of the plastic recycling processes that deliver a mechanically sustainable product and may be used for 4D printing applications, such as self-assembly, sensors, actuators, and other engineering applications. The success and implementation of 4D printing are dependent on the tendency of the shape memory with the action of external stimuli, such as heat, force, fields, light, and pH. Acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) are the most common materials for fused filament fabrication-based 3D printing processes. However, the low-shaped memory tendency on heating and weaker and less rigidity of ABS limit the application domains. PLA is an excellent responsive behavior when the action of heat has high stiffness. The incorporation of PLA into ABS is one of the solutions to tune the shape memory effect for better applicability in the 4D printing domain. In this study, the primary recycled PLA was incorporated into the primary recycled ABS matrix from 5 to 40% (weight%), and composites were made by extrusion in the form of cylindrical filaments for 4D printing. The tensile and shape memory properties of the recycled ABS–PLA composites were investigated to select the best combination. The results of the study were supported by fracture analysis by shape memory analysis, scanning electron microscopy, and optical microscopy. This study revealed that the prepared ABS–PLA-based composites have the potential to be applied in self-assembly applications.

Advanced drug delivery technologies for postmenopausal effects

Postmenopause is the 12-month absence of menstrual periods, characterized by decreased estrogen and progesterone levels, leading to physical and psychological alterations such as hot flashes, mood swings, sleep disruptions, and skin changes. Present postmenopausal treatments include hormone replacement therapy, non-hormonal drugs, lifestyle modifications, vaginal estrogen therapy, bone health treatments, and alternative therapies. Advanced drug delivery systems (ADDSs) are essential in managing postmenopausal effects (PMEs), offering targeted and controlled delivery to alleviate symptoms and improve overall health. This review emphasizes such ADDSs for addressing PMEs. Emerging trends such as artificial ovaries are also reviewed. Additionally, the prospects of technologies such as additive manufacturing (3D and 4D printing) and artificial intelligence in further tailoring therapeutic strategies against PMEs are provided.

Helical Micropillar Processed by One-Step 3D Printing for Solar Thermal Conversion.

Solar thermal utilization has broad applications in a variety of fields. Currently, maximizing the photo-thermal conversion efficiency remains a research hotspot in this field. The exquisite plant structures in nature have greatly inspired human structural design across many domains. In this work, inspired by the photosynthesis of helical grass, a HM type solar absorber made in graphene-based composite sheets is used for solar thermal conversion. The unique design promoted more effective solar energy into thermal energy through multiple reflections and scattering of solar photons. Notably, the Helical Micropillar (HM) is fabricated using a one-step projection 3D printing process based on a special 3D helical beam. As a result, the solar absorber's absorbance value can reach 0.83 in the 400-2500nm range, and the surface temperature increased by ≈128.3% relative to the original temperature. The temperature rise rate of the solar absorber reached 22.4°Cmin-1, demonstrating the significant potential of the HM in practical applications of solar thermal energy collection and utilization.

Stereolithography 3D Printing of Stimuli-Responsive Spin Crossover@Polymer Nanocomposites with Optimized Actuating Properties.

We used stereolithography to print polymer nanocomposite samples of stimuli-responsive spin crossover materials in the commercial photo-curable printing resins DS3000 and PEGDA-250. The thermomechanical analysis of the SLA-printed objects revealed not only the expected reinforcement of the polymer resins by the introduction of the stiffer SCO particles, but also a significant mechanical damping, as well as a sizeable linear strain around the spin transition temperatures. For the highest accessible loads (ca. 13-15 vol.%) we measured transformation strains in the range of 1.2-1.5%, giving rise to peaks in the coefficient of thermal expansion as high as 10-3 °C-1, which was exploited in 3D printed bilayer actuators to produce bending movement. The results pave the way for integrating these advanced stimuli-responsive composites into mechanical actuators and 4D printing applications.

Shape Memory Polymers in 4D Printing: Investigating Multi-Material Lattice Structures

This paper evaluates the design and fabrication of a thermoplastic polyurethane (TPU) shape memory polymer (SMP) using fused deposition modeling (FDM). The commercially available SMP filament was used to create parts capable of changing their shape following the application of an external heat stimulus. The characterization of thermal and viscoelastic properties of the SMP TPU revealed a proportional change in shape fixity and recovery with respect to heating and cooling rates, as well as a decreasing softening temperature with increasing shape memory history due to changes in the polymer microstructure. Inspired by the advancements in 3D and 4D printing, we investigated the feasibility of creating multi-material lattice structures using SMP and another thermoplastic with poor adhesion to TPU. A variety of interlocking lattice structures were evaluated by combining SMP with another thermoplastic that have poor adhesion with TPU. The tensile strength and failure modes of the fabricated multi-material parts were compared against homogenous SMP TPU specimens. It was found that the lattice interface failed first at approximately 41% of the ultimate strength of the homogenous part on average. The maximum recorded ultimate strength of the multi-material specimens reached 62% of SMP TPU’s ultimate strength. These characterizations can make 4D printing technology more accessible to common users and make it available for new markets.