3D Printing Process Research Articles

“All-in-one” ink for light-based 4D printing of conducting, tough, anti-freezing, and cytocompatible hydrogels

High-performance hydrogel-based electronic devices require conducting hydrogels. Conducting hydrogels that are stretchable, soft, and biocompatible are in much demand to fabricate human–machine interfaces, wearable devices, soft robotics, and many other applications. We present a new generation polymeric formulation to prepare hydrogels by digital light processing (DLP)-based three-dimensional (3D) printing technology with visible light that are anti-freezing, electrically conductive, tough, stretchable, and non-toxic. The printed conducting hydrogels have exceptional water-holding capability at atmospheric conditions and tolerance to freezing over a wide range of temperatures from − 80 to 45 °C. The inks are amenable to the manufacturing of four-dimensional (4D)-printed hydrogels that can elicit pre-programmed structural deformations. This work presents polymeric formulations for potentially designing ultrafast programmable electronic devices with printed hydrogel electronics in various biomedical applications, soft robotics, biosensors, flexible electronics, human–machine interfaces, and health monitors for use under extreme environmental conditions.

Investigations into 4D printed PLA/graphite composite with thermal induced shape memory effect

PurposeThe paper aims to fabricate shape memory composites using polylactic acid (PLA) matrix and graphite. Shape memory polymers are a promising family of materials for biomedical applications because of their favourable mechanical properties, fast reactions and good biocompatibility. For most SMPs, however, achieving controllable sequential shape change is challenging.Design/methodology/approachIn the present work, 4D printing technology is used to fabricate shape memory composites using polylactic acid (PLA) matrix and graphite. A comparative study of pure PLA and graphite’s different weight % composition has been done.FindingsBy carefully managing the deformation state, PLA with graphite shape memory composites produced controllable sequential deformation with an amazing shape memory effect. Surface morphology, thermal properties, melt flow index and shape recovery tests have all been carried out to assess the qualities of manufactured samples.Originality/valueThis is a one-of-a-kind to fabricate shape memory composites using graphite and a PLA matrix. Thus, this research attempts to deliver the possible use of PLA/graphite composites fabricated using 4D printing in robotics and biomedical devices.Graphical

Hierarchical Composites Patterned via 3D Printed Cellular Fluidics

AbstractAdditive manufacturing of freeform structures containing multiple materials with deterministic spatial arrangement and interactions remains a challenge for most 3D printing processes, due to complex fabrication tool requirements and limitations in printability of some material classes. Here, a versatile method is reported to produce architected composites using the concept of cellular fluidics, in which lattices of unit cells are used as templating scaffolds to guide flowable infill materials in a programmed spatial pattern, upon which they are cured in place to produce a deterministically ordered multimaterial solid. The lattice design relies on the unit cell size, type, strut diameter, surface wetting, and distribution of cellular structures to control liquid flow and retention. Individual unit cells are tuned to achieve reliable infilling and combined into higher‐order architectures to achieve multiscale composite materials with disparate mechanical properties, including those considered non‐printable. Lattice design considerations for leveraging capillary phenomena and demonstrate several methods of patterning polymers in 3D‐printed cellular fluidic structures are presented. The concept of tuning the compressive response of an architected composite using a flexible‐elastomer as the lattice and a stiff‐epoxy as the infill material is illustrated.

A new approach for heat transfer coefficient determination in triply periodic minimal surface-based heat exchangers

The development of additive manufacturing offers increasing opportunities in heat transfer. A wider range of materials is used in the 3D printing process of heat exchangers based on the Triply Periodic Minimal Surface. Due to the complexity of these structures, it is difficult to precisely determine the values describing the heat transfer process in these devices. One of the parameters describing the heat transfer process in heat exchangers is the heat transfer coefficient. This study describes a new method for determining the heat transfer coefficient in a heat exchanger based on a gyroidal lattice. The proposed new method allows for determining the heat transfer coefficient values without interfering with the internal space of the compact heat exchanger. The developed formula can be used in the indirect method of determining the value of the heat transfer coefficient in two-phase flow with boiling or condensation of the working medium. The thermal tests were carried out in the range of working flow rates 4–24 kg/h; the media temperature was 20 and 50 °C, the heat flux was from 0.1 to 0.4 kW. Tests were conducted for laminar flow in the 20 < Re < 200 range.

The comprehensive review on 3D printing- pharmaceutical drug delivery and personalized food and nutrition

Three-dimensional printing is one of the emerging technologies that is gaining interest from the pharmaceutical industry as it provides an opportunity to customize drugs according to each patient's needs. Combining different active pharmaceutical ingredients, using different geometries, and providing sustained release enhances the effectiveness of medicine. One of the most innovative uses of 3D printing is producing fabrics, medical devices, medical implants, orthoses, and prostheses. This review summarizes the various 3D printing techniques such as stereolithography, inkjet printing, thermal inkjet printing, fused deposition modelling, extrusion printing, semi-solid extrusion printing, selective laser sintering, and hot-melt extrusion. Also, discusses the drug relies profile and its mechanisms, characteristics, and applications of the most common types of 3D printed API formulations and its recent development. Here, Authors also, summarizes the central flow of 3D food printing process and knowledge extension toward personalized nutrition.

Path planning and inspection of complex-shaped 3D-printed composites based on robotic pulse-echo laser ultrasonic testing

With the recent advancement in manufacturing, there has been an increasing demand for composite workpieces in the aviation industry. The emergence of composite 3D printing technology that enables the simplification and automation of composite manufacturing processes presents the possibility of replacing the manufacturing process of secondary structures in an unmanned aerial vehicle (UAV). To evaluate the applicability of the technology, a solution for automated non-destructive testing (NDT) that can be applied after the 3D printing process is needed. This study proposes an advanced approach to utilizing laser ultrasonic testing (LUT) for complex-shaped structures fabricated through continuous fiber 3D printing. To ensure accurate defect detection and localization, which are crucial factors in NDT, we propose a method that utilizes a six-degree-of-freedom (6-DOF) robot arm to control the position of the inspection target. By calculating the scan points and path through coordinate transformation and spatial rotation using a quaternion, all surfaces of the targets were inspected. This maintains a constant stand-off distance (SOD) while the sensing laser was vertically incident on the target surface, resulting in a high signal-to-noise ratio (SNR) of the ultrasonic signals. Inspection results have demonstrated the proposed technique to be suitable for detecting defects in complex-shaped 3D-printed structures.

Prediction of effective parameters for 3D printing of poly lactic acid-carbon fibre composites using intelligent frameworks based on mechanical response

Purpose This paper aims to find the effective 3D printing process parameters based on mechanical characteristics such as tensile strength and hardness of poly lactic acid (PLA)/carbon fibre composites (CF-PLA) by implementing intelligent frameworks. Design/methodology/approach The experiment trials are conducted based on design of experiments (DoE) using Taguchi L9 orthogonal array with three factors (speed, infill % and pattern type) and three levels. The factors have been optimized by solving the regression equation which is obtained from analysis of variance (ANOVA). The contour plots are generated by response surface methodology (RSM). The influencing parameters are found by using Box–Behnken design. The second order response surface model demonstrated the optimal combination of input parameters for higher tensile strength and hardness. Findings The influencing parameters are found by using Box–Behnken design. The second order response surface model demonstrated the optimal combination of input parameters for higher tensile strength and hardness. The results obtained from RSM are also confirmed by implementing the machine learning classifiers, such as logistic regression, ridge classifier, random forest, K nearest neighbour and support vector classifier (SVC). The results show that the SVC can predict the optimized process parameters with an accuracy of 95.65%. Originality/value 3D printing parameters which are considered in this work such as pattern types for PLA/CF-PLA composites based on intelligent frameworks has not been attempted previously.

Operando Colorations from Real-Time Growth of 3D-Printed Nanoarchitectures.

While artificial 3D nanostructures can generate precise and flexible coloration, their real-time color changes during 3D nanoprinting remain unexplored owingto the inherent challenges of in situ transient measurements and observations. In this study, a 3D-printing system which supports the operando observation/measurement of the color dynamics of subwavelength metallic nanoarchitectures fabricated in real time is developed and evaluated. During 3D printing, the dimensions and geometries of the 3D nanostructures grow over time, producing a large library of optical spectra associated with real-time color changes. Only a timer is needed to define the expected colors from a single 3D print run. Fin-like nanostructures are used to toggle colors based on the polarization effect and produce color gradients. Based on structural coloration, nanoarchitectures are designed and printed to animate desired color patterns. Moreover, the resulting color dynamics can also serve as an operando identifier for real-time structural information during 3D nanoprinting. A single print run enables the efficient creation of a comprehensive library of desired colorations owing to the flexibility in time-dependent controllability and 3D geometries at the subwavelength scale. 3D nanoprinted plasmonic structures exhibiting time-varying colorations (4D printing of colors) uniquely redefines the coloring stategy,offering considerable potential for numerousapplications.

Low-cost method to reduce interlayer voids in material extrusion: in situ layer-by-layer solvent treatment

Material extrusion (MEX) is worldwide known as one of the most flexible additive manufacturing (AM) technologies for the fabrication of complex polymeric structures. However, the extremely high geometrical freedom has a price to pay: the presence of interlayer voids between consecutive extruded layers is the main backwards of MEX technology. Interlayer voids make 3D printed parts weaker (poor mechanical properties) compared to polymeric components fabricated by means of counterpart processes (i.e., injection molding). The present research work introduces a novel approach for the reduction of voids based on the layer-by-layer application of solvent vapor during the fabrication process, to smooth every single deposited layer. In this way, the new extruded layer has a greater area to bond with the previously extruded layer, resulting in an overall reduction of the porosity. The proposed approach is cost-effective, and it is based on the stop and go method enabled by MEX technologies: the fabrication process is paused after every layer, and when the solvent treatment is performed, the 3D printing process is resumed. The effectiveness of the layer-by-layer solvent vapor approach was evaluated, thereby resulting in a great reduction of the void density and average void area of 96%, and 79% respectively, and an increase of the wetting factor of 34%. Such findings pave the way for the exploitation of the proposed approach for the fabrication of complex structures with a reduced number of voids to be employed as structural components.

A Statistical Investigation and Prediction of the Effect of FDM Variables on Flexural Stress of PLA Prints

Due to its many engineering applications, low manufacturing costs, and environmental friendliness, 3D printing is considered one of the most promising manufacturing technologies. The quality of printed parts will inevitably be affected by the controllable variables used in the 3D printing process. The present study aims to investigate how different printing process parameters affect the bending strength of PLA prints. The ASTM D790 standard was used to fabricate the samples in this work, while the Taguchi principle was used to design the experiments. The following values were chosen: shell width (0.8, 1.2, 1.6, and 2 mm), layer thickness (0.15, 0.2, 0.25, and 0.3 mm), and infill density (40%, 60%, 80%, and 100%). The results showed that fill density is the most effective variable for improving bending strength. Measurements of infill density (100%), layer thickness (0.15 mm), and shell width (2 mm) gave the best results, which were calculated to be 83.1479 MPa in bending test. The mathematical model in this study was developed using linear regression analysis, and the residuals confirmed that the model fit the data well, with a maximum error of 6.1%.

Structural design of a novel rotary platform 3D printer

Abstract Stair-stepping defects in 3D printing processes can be caused by various reasons, such as the quality of the printing material, the position of the print head, printing speed, printing temperature, and so on. To improve the issue of stair-stepping effects in thin-walled revolving parts during the 3D printing process, this project aims to design a 3D printer that enables the print head to move in the X, Y, and Z axes while the heated bed platform can rotate. This will significantly reduce the stair-stepping effect’s impact and greatly enhance the printing’s quality and accuracy.

Breaking the limitation of terahertz resonances in ferrites through 4D printing of metamaterials

4D printing allows the creation of 3D-printed structures with a variety of new functionalities that respond to external stimuli, including electromagnetic properties, for which research is limited, such as terahertz resonances in ferrite materials; and therefore holding great promise for a wide range of applications. However, the limited physical properties of ferrite materials, including their anisotropic properties and limited material manipulation space, pose significant challenges to the development of ferrite materials designed for progressively increasing terahertz frequencies. Therefore, this paper proposes a platform for overcoming the limitations of terahertz resonance in ferrites through the 4D printing of metamaterials. Both the elastic and viscous moduli of the slurry are sensitive to the applied shear stress; as this stress increases, these moduli sharply decrease by several orders of magnitude, resulting in the transformation of the slurry into a fluid state similar to the liquefaction of ink. Electromagnetic coupling modes between electric dipoles and magnetic dipoles endow these ferrite metamaterials with induction and switching of terahertz resonances due to orientation stimulation. Our work sheds light on the creation of electromagnetic properties and their control by 4D printing.

Computed tomography imaging analysis of a fused filament fabrication (FFF) 3D printed neck-thyroid phantom for multidisciplinary purposes

The application of the 3D printing technique for the development of low-cost phantoms is being investigated recently and requires a complex study of the interaction of printed materials with different types and qualities of radiation, as well as the characterization of printing filaments to correctly simulate human tissue attenuation. This study aims to present the Computed Tomography (CT) Imaging analysis of a fused filament fabrication (FFF) 3D printed anthropomorphic neck-thyroid phantom. The commercial phantom ATOM MAX 711 from CIRS was used as anatomy of reference for the 3D modeling base of the neck-thyroid phantom. Commercially available PLA and ABS XCT-A validated at IPEN were used in the 3D printing process in order to simulate soft and bone tissues respectively. The printing process was done using the RAISE3D PRO 2 FFF printer from IPEN. The imaging study of the phantom was performed through the analysis of images from a CT acquisition, comparing the Hounsfield Units (HU) numbers of the tissues between both CIRS and 3D printed phantoms. The developed phantom is a feasible alternative and presents some desirable characteristics for applications in radiation protection, measurements of radioisotopes incorporated in the thyroid (both contamination counters and nuclear medicine detectors) and training of techniques of acquisition of images with X rays.

PH-Sensitive Polymers with their Important Applications (A Review)

Abstract:: Materials that modify their chemical or physical characteristics in reaction to diverse stimuli, such as moisture, heat, water, or pH, are commonly known as smart materials or stimuli-responsive polymers. Typical applications for these polymers include catalysis, finishing, and coating processes. Tissue engineering, drug delivery, and gene transportation are additional applications that have emerged in the past two decades. As a result, their potential use extends to a wider range of applications, encompassing chemical processes, drug delivery, body-site targeting, separation, membrane activity, sensing and actuation, and agriculture. Recently, pH-responsive polymers have garnered considerable interest for implementation in membrane and 4D printing. The current review work encompasses previously published research through 2022, with a particular focus on the critical application of pH-sensitive polymers.

Electrically/Magnetically Dual‐Driven Shape Memory Composites Fabricated by Multi‐Material Magnetic Field‐Assisted 4D Printing (Adv. Funct. Mater. 27/2024)

Electrically/Magnetically Dual‐Driven Shape Memory Composites Fabricated by Multi‐Material Magnetic Field‐Assisted 4D Printing (Adv. Funct. Mater. 27/2024)

Design of a Radar Signature Measurement Model of an Unmanned Aerial Vehicle with Low Radar Signature

Existing databases of RCS benchmarks lack a complex, low-observable target. This paper describes the design of such a complex and low-observable measurement model. Starting point of the design is the so-called Muldicon model, developed by the NATO/STO/AVT panel. Hot spots of the original model are identified and treated with radar-absorbing materials. Simulations on the treated model demonstrate that the model is indeed low observable. The effect of the manufacturing process of 3D-printing and separable parts is assessed experimentally on a cone-sphere; the effect is found to be negligible. These results give confidence that the model, when built, satisfies the requirements of being complex and low observable; and that artefacts of the manufacturing process will not impair its signature.

Effect of moisture content on the mechanical performance of 3D printed continuous reinforced two-matrix composite

Additive manufacturing, particularly Fused Filament Fabrication, has gained significant attraction in recent years. In order to increase the mechanical performances of several components, continuous reinforcements, such as carbon fibers, can be coextruded with a polymeric matrix.The present study relies on a specific 3D printing process, called towpreg coextrusion, which exploits continuous carbon fibers covered with an epoxy resin and polyamide (PA) as the thermoplastic matrix, thus obtaining a 3D printed two-matrix composite. Since polyamide is a highly hygroscopic material, the impact of moisture content on the mechanical properties of 3D-printed continuous composites was investigated. Tensile and flexural specimens were manufactured and tested under both undried and dried conditions. Drying treatment was carried out at a temperature of 70 °C for 2 h in oven, with weight measurements before and after for quantifying weight loss and then the moisture removal. Additionally, through thermogravimetric analysis, the thermal stability of the material was assessed. It was observed that the drying process allows for a reduction of up to 0.56% by weight of moisture in the specimens. Thus, the drying process led to an improvement in the mechanical properties of the material. Specifically, the tests reveal a 15% increase in tensile strength and an 11.5% increase in flexural strength following the drying process, reaching values of 392.78 MPa and 151.06 MPa, respectively. Similarly, an increase in the tensile and flexural moduli was noted in the treated specimens. Finally, fractured samples underwent optical and scanning electron microscopy analysis, through which different fracture mechanisms of the material and the presence of macrovoids and microvoids attributable to the 3D printing process were observed. Knowledge of deposition defects represents an important starting point for the improvement of the process and the mechanical properties obtained to date. This research provides valuable insights into optimizing 3D-printed continuous composites, emphasizing the importance of moisture control for superior mechanical performance in industrial applications.

4D Printing: Bridging the Gap between Fundamental Research and Real-World Applications

The Special Issue “4D Printing: State-of-the-art, Recent Trends, and Applications” highlights the significant impact of scientific advancements on practical and innovative applications. It focuses on the interdisciplinary challenges of multi-material printability on a voxel basis and optimizing the actuation performance of composite structures with various stimuli. Key considerations, such as mechanical strength and potential adverse effects, shape the design methods suited to specific quantitative data limitations. Four-dimensional printing calls for creativity, interdisciplinary collaboration, and practical applications. While recognizing experience-based approaches in research, this review paper emphasizes integrating science and technology through alternative strategies; innovative approaches; and the exploration of engineering, design, and artificial intelligence.

Determining technological parameters for obtaining ta15 titanium alloy blanks with improved mechanical characteristics using the electron-beam 3D printing method

The object of this study is the process of electron beam 3D printing of articles made of TA15 titanium alloy powder. Peculiarities of the structure and properties formation of alloy blanks, obtained by this method have been described. Influence of process parameters (electron beam power and geometric scanning parameters) on the characteristics of the material were considered. Step of displacement of the beam trajectory changed from 0.1 to 0.25 mm with an interval of 0.05 mm. Specific energy of the electron beam varied from 20 to 70 J/mm3 for every trajectory displacement step. The macrostructure was examined visually while the microstructure was studied by optical microscopy. Mechanical properties were determined by uniaxial tension and impact bending tests. It was established that depending on the 3D printing parameters the macrostructure of most samples is dense but with unfavorable parameters non-fusions or shrinkage porosity defects may form. The microstructure of the dendritic type has an α´+β lamellar-acicular morphology, its dispersity and shape of α´–phase areas vary depending on the process parameters. A scanning step of 0.2 mm and a beam energy of 40 J/mm3 allows obtaining a dispersed microstructure in which there are no non-fusions and shrinkage micropores. The value of the Rm is 27 %, and the R0.2 is 24 % higher than that of the alloy obtained by the conventional technology of electron beam melting. The A5 is 3.2 times higher. However, impact toughness of the sample with dendrite unfavorable orientation to the direction of load applying may be lower compared to conventional technology. The results could be used for devising commercial technology of high strength titanium alloys parts produced by 3D printing

3D printing technology for the design of eco-friendly palisade solar evaporators for enhanced desalination and wastewater treatment

Solar-driven desalination represents a promising solution to the global water scarcity challenge, offering a sustainable and efficient method for water purification. However, traditional solar evaporation techniques face several hurdles, including prohibitive costs, intricate fabrication processes, and suboptimal solar-to-thermal energy conversion efficiencies. Addressing these issues, our study introduces an innovative, low-cost, and high-efficiency palisade solar evaporator, created using a one-step fused deposition modeling (FDM) 3D printing process. This method requires only a straightforward hot water treatment for post-fabrication conditioning, avoiding the need for complex preparations or modifications. The evaporators are very eco-friendly, as they are printed using commercial and biodegradable polylactic acid (PLA) containing carbon fibers. The structural parameters of palisade solar evaporators, including height and gap size, were well optimized. The palisade solar evaporator with height of 18 mm and gap width of 0.6 mm exhibits a solar-driven water evaporation rate of 2.52 kg m−2 h−1 under one sun illumination. Moreover, the device demonstrates exceptional salt resistance, maintaining its efficiency without salt buildup or performance degradation over prolonged use. This investigation validates the feasibility of utilizing commercial and biodegradable PLA in 3D printing to develop cost-effective, eco-conscious, and efficient solar evaporators for desalination and wastewater treatment.