Printing Nozzle Research Articles

Conical Annular Nozzle Pressure Prediction and Applications to 3D Food-Printing for Dysphagia Diets

In order to solve the dietary problems of patients with dysphagia, a mathematical model for predicting extrusion pressure is established. The predictive model parameters are determined with the aid of the finite element method, and a 3D printing nozzle capable of printing nutrient-rich sandwich food is designed according to the predictive model. Pumpkin puree and minced pork are verified according to IDDSI standards. Finally, the accuracy of the predictive model and the printing effect of the design nozzle are verified by extrusion and printing experiments, respectively. The results show that four groups of simulation experiments reveal that the extrusion pressure increases by 15.6%, 13.5%, 12.7% and 12.4%, respectively, with a 1 cm increase in nozzle length. When the nozzle length is in the range of 1–5 cm, the extrusion pressure increases with the increase of the volume flow rate in the extrusion cylinder. The extrusion speed has little correlation with the length of the nozzle outlet, but for every 1 cm3/s increase in the inlet volume flow rate, the extrusion speed increases by about 1.5%. The finite element simulation experiment determines that the parameters of the prediction model are σ0 = 0.6, α = 1.1, m = 0.21, τ0 = 0, β = 0.52 and n = 0.2; the error between the predictive value and the experimental value is 15%, and the printed sandwich food has smooth lines, good molding and complies with IDDSI standards.

A multivariate study on the effect of 3D printing parameters on the printability of gluten-free composite dough.

The advancement of three-dimensional (3D) food printing technology is significantly influencing the food processing industry. The present study utilized extrusion 3D printing to create a gluten-free dough composed of little millet flour (LMF), amaranth seed flour (ASF) and curry leaf flour (CLF). The primary objective was to elucidate the effects of various extrusion-based 3D printing conditions, including extruder nozzle diameter (ND), extrusion rate (ER), print speed (PS) and layer height (LH) on the printability parameters of the dough. In this study, three formulations of composite dough were prepared (i.e., S1, S2 and S3) by varying LMF, ASF and CLF compositions; among which S1 composite (LMF:ASF:CLF::30:60:10 w/w) was found to have comparable viscoelastic properties with the wheat dough. Central composite design (CCD) was selected with 30 experimental runs and 3D dough samples were printed using S1 composite by varying ND, ER, PS and LH. Principal component analysis of the printed samples accounted for 82.75% of variability and classified the samples into three confidence ellipses. From the results of the CCD model, four solution parameters in terms of ND:ER:PS:LH::mm: pulse μL-1:mm s-1:%, namely, P1 (1.8:115:8:70), P2 (1.6:115:7.8:65), P3 (2:100:7.8:55) and P4 (2:105:6.2:75), with high desirability value (> 0.85) were selected for sample 3D printing and post-baking analysis. The P1 sample was found to have least print deformations, highest print fidelity (85.66%), and lowest hardness (55.95 N) and fracturability (39.66 N) values, and hence was selected as optimized product. The present study provides parametric solutions for efficient 3D printing of gluten-free composite dough, aligning with the increasing dietary preferences and demand of novel functional customized foods. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Experimental, numerical and optimization investigation of sandwich structures with 3D-printed sacrificial core under explosive loading

Sandwich panel structures are widely used in aerospace, marine, and automotive applications due to their high stiffness, high strength-to-weight ratio, good vibration damping, and thermal conductivity. The present study investigates the response of 3D printed polylactide acid (PLA) honeycomb structures when used as a crushable core with a protective metal coating in order to analyze the extent of damage and deformation of the center of the back sheet. This research is based on experimental testing and finite element simulation. The purpose of this study is to investigate the effect of three parameters of sandwich panel core, including filling density of the sacrificial core, 3D printer nozzle thickness, and the geometry of printed cells on the strength of sandwich panel under explosive loading. In this study, the effect of these three parameters is investigated at the same time, and finally, the optimal state of these three parameters that leads to the least displacement of the center of the back sheet is introduced. At first, a sandwich structure with a honeycomb core was made by a 3D printing machine, and the filling density of the core was 13 %. Then this set was subjected to explosive loading in open air with C4 explosive and the displacement of the center of the back sheet was measured. Further, considering the cost of experimental tests, the conditions of this test were simulated by the finite element code in LS-DYNA software, and the results of the displacement of the center of the back sheet were verified by experimental testing. In the following, Design-Expert software was used to check the three parameters of filling density, geometry of cells and thickness of the 3D printer nozzle at the same time. Finally, to verify the value obtained for the optimal state, the finite element simulation and experimental test were performed by placing the input parameters of the optimal state and the results were compared.

Refined dimensional accuracy in FDM components via ensemble weight-optimized surrogates and hybrid NSGA-II-TOPSIS optimization

ABSTRACT In this paper, a novel approach was developed to predict the geometrical deviation and density of fused deposition modeling (FDM) parts and to optimize these outcomes by fine-tuning the relevant process variables. The prediction process utilized an ensemble approach, combining the optimized weighted sum of three individual surrogate models. These models correlate the input variables – nozzle temperature (NT), infill fraction (IF), and print speed (PS) – with the output responses of density, internal ovality (IO), and external ovality (EO). According to the results, the ensemble outperformed the individual surrogates, exhibiting enhanced predictive accuracy. Subsequently, non-dominated sorting genetic algorithm II (NSGA-II), a multi-objective optimization technique, was integrated with the technique for order of preference by similarity to ideal solution (TOPSIS), a multi-criteria decision-making method, to optimize the ensemble of surrogates (EoS) and generate a ranked set of Pareto-optimal solutions. The outcomes from the EoS, combined with the NSGA-II-TOPSIS hybrid optimization process, revealed that the most effective optimal control parameters were approximately 195°C for NT, 50% for IF, and a range of 55–66 mm/min for PS. This hybrid approach affirmed the reliability and robustness of the identified processing parameters for the production of top-quality FDM parts with desired dimensional accuracy and density.

Extrusion-Based Three-Dimensional Printing of Metronidazole Immediate Release Tablets: Impact of Processing Parameters and in Vitro Evaluation

PurposeThe current study assessed the potential of a pneumatic 3D printer in developing a taste-masked tablet in a single step. Metronidazole (MTZ) was chosen as the model drug, and Eudragit® E PO was used as a taste-masking polymer to produce taste-masked tablets.MethodsThe study focused on optimizing processing parameters, such as the nozzle's printing speed, the printhead's heating temperature, and the pressure. Oval-shaped tablets were printed with a rectilinear printing pattern of 30% and 100% infill and evaluated for in vitro drug release and taste masking. The 3D-printed tablets are also characterized using Differential Scanning Calorimetry (DSC), Fourier-transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM).ResultsThe infill density impacts the drug release profile of the tablets. F9, F10, and F11 displayed desired printability among the formulations, with F9 and F10 exhibiting over 85% drug release within 60 min in the in vitro dissolution study. The F9 formulation, with 30% infill, effectively masked the bitter taste of MTZ in the in vitro dissolution study carried out in a pH 6.8 artificial salivary medium. The observed release was below the tasting threshold concentration of the model drug.ConclusionIn summary, 3-dimensional extrusion-based printing combines the effects of hot-melt extrusion and fused deposition modeling techniques in a single-step process, demonstrating potential as an alternative to the fused-deposition model 3D printing technique and warranting further exploration.Graphical

A friction-based method for measuring the radial compaction response of fibre tows

High performance fibre reinforced composite components are typically compacted to a high fibre volume fraction during manufacture. As such, it is important to understand the compaction behaviour of these materials to better design and model composite manufacturing processes. While most manufacturing processes apply transverse compaction pressure to planar textiles, continuous fibre composite 3D printing processes can apply a radial compaction pressure to a single tow in the printing nozzle. A similar mode of compaction is also seen in processes such as pultrusion of circular cross-sections. This work describes a new friction-based method for measuring the radial compaction response of single tows, or groups of tows. The radial compaction behaviour of a single 40K carbon fibre tow is measured and presented. Radial compaction of the characterised tow showed a steeper nonlinear relationship between compaction pressure and fibre volume fraction, than typically found for transverse compaction of 2D textile reinforcements.

Development of beetroot powder-enriched inks for 3D food printing based on hydrogel/oleogel bigels

3D printing with bigel inks exhibits substantial potential for food structuring and nutritional innovation, particularly through the enrichment of foods with vegetables rich in health-promoting bioactive compounds. This study focuses on the preparation of bigels incorporating beetroot powder. Hydrogels based on xanthan gum, carrageenan, and guar gum were used in combination with monoglyceride oleogels to formulate suitable inks for extrusion-based 3D food printing. This study investigated the effects of hydrogel type, vegetable powder content, and hydrogel:oleogel mass ratio on the microstructure, rheological properties, and extrusion behavior of the bigels. Furthermore, the printability of the selected formulations was evaluated. The inclusion of beetroot powder enhanced the structure and mechanical strength of all the hydrogels. Bigels prepared with an 80:20 mass ratio yielded homogeneous materials for all three hydrogelators. They exhibited maximum storage modulus values of 1.1E4, 7.8E3, and 3.3E3 Pa for guar gum, carrageenan, and xanthan gum, respectively. Moreover, these bigels partially recovered of their initial structure after the application of high strain and demonstrated appropriate flowability for extrusion through 1.2 and 2 mm 3D printer nozzles. Successful printing of 2D (grid) and 3D (cube) structures was achieved using guar gum-based bigels, followed by carrageenan-based counterparts, which displayed superior dimensional accuracy, structural integrity, enhanced line resolution, and minimal printing errors and deformations. These findings provide valuable insights and lay the groundwork for developing more complex and functional food structures.

Dispense Printing of Silver Flake Inks on Hydrophilic and Hydrophobic Surfaces

In printed electronics, achieving precise deposition of conductive materials on challenging substrates like Teflon is critical. This study delves into dispense printing, a technique that offers precision and versatility for creating electronic patterns. The deposition of high‐viscosity silver flake inks on both hydrophobic surfaces is investigated, such as Teflon, and hydrophilic ones, highlighting the significant interplay between ink viscosity and substrate wettability. This interaction is key to controlling ink spreading, drying behavior, and, ultimately, printing success. Research explores the relationships between critical parameters such as nozzle height, dispense pressure, and print speed, aiming to enhance the quality and functionality of printed electronics. The printing process is analyzed through its distinct phases: extrusion from the nozzle, spreading on the substrate, and line shrinking during drying. This methodological approach allows one to pinpoint how each parameter specifically influences the printing outcome, particularly on challenging substrates like Teflon. By advancing the understanding of these dynamics, the study offers valuable theoretical insights and practical advancements for fabricating high‐quality, flexible electronics across diverse substrates. The findings underscore dispense printing's potential to meet the growing demand for flexible electronics.

Enhancement of structural properties of 3D-printed plant-based meat analogs by TGase/laccase

As we all know, achieving the desirable texture and fibrous structure of 3D-printed meat analogs has been challenging. Therefore, this study aimed to investigate the effect of transglutaminase (TGase) or laccase on printability, texture, and structure of 3D-printed soy protein isolate (SPI) -wheat gluten (WG) -insoluble dietary fiber (IDF) plant-based meat analogs (PBMA). Results showed that TGase significantly improved the hardness, gumminess, and chewiness of PBMA (p < 0.05), whereas laccase exhibited an opposite trend. The tensile strength and elongation at break were increased by TGase or laccase, with laccase exhibiting better effect (9.37 ± 0.25 kPa, 63.16 ± 3.18%). The interaction of laccase and IDF resulted in the maximum value of apparent viscosity and disulfide bond content, which hindered the movement of printed materials through the printing nozzle, and potentially led to PBMA incomplete-structure. Synergistic effect of TGase and IDF has been shown to enhance the content of hydrogen, hydrophobic, and disulfide bonds. This combination readily induced an increase in α-helix and β-sheet formations, promoting a more orderly development of the protein structure, consequently, the internal architecture became more uniform and densely packed. These results indicated that TGase treatment combined with IDF might be a novel and promising strategy to enhance the texture and structure of PBMA.

Dynamics of non-Newtonian fluid–fiber interactions and void formation mechanism based on fused filament fabrication

Due to the presence of internal defects such as voids in the composites manufactured by material extrusion additive manufacturing (MEX AM), the mechanical properties of the composites are significantly below the theoretical optimum. Under this circumstance, this paper is intended to investigate the effects of nozzle feeding angles and to analyze the void formation and evolution of multiphase flow, in which systematic computational fluid dynamics numerical simulations are conducted. The volume of fluid model and overset grid method are used to simulate the extrusion deposition process of carbon fiber-reinforced polymer composites, and the Carreau model is used to represent the shear-thinning behavior of molten polymer. The numerical method is validated against previously experimental and numerical simulation data. The numerical results show that the key factor leading to void formation is the vortices caused by fiber oscillation. The intense vortex at the front end of the fibers disrupts the interface between molten polymer and air, creating a beneficial condition for air to enter. Nozzle tilting can effectively reduce the probability of void formation by decreasing the fiber oscillation velocity. The results of the present study provide insights into the development and optimization of printer nozzles to enable the printing of longer fibers with less probability of potential void formation.

Ultrasonic vibration-assisted high-resolution electrohydrodynamic (EHD) printing

Electrohydrodynamic (EHD) printing has become a promising and cost-effective technique for producing high-resolution and large-scale features. One widely recognized obstacle in EHD printing is nozzle clogging due to solvent evaporation or ink polymerization. Moreover, printing highly viscous materials often requires pressure or other external force to assist the ink flow during the printing, which increases the complexity of process control and the required energy. In this work, we developed a novel ultrasonic vibration-assisted EHD printhead and associated process to effectively eliminate the nozzle clogging for the printing of high-viscosity and high-evaporation-rate inks. A series of experimental tests were conducted to characterize the printhead design and process parameters (i.e., vibration frequency, vibration amplitude, and printing voltage). The results demonstrated that superimposing ultrasonic vibration on the EHD printing nozzle can effectively enhance current EHD printing capabilities, such as reducing required pressure, eliminating nozzle clogging, and providing stable and continuous printing for high viscosity and high solvent evaporation rate material. With the optimal parameters, a filament with a diameter of around 1 µm can be continuously printed. In the paper, we successfully applied this developed ultrasonic-assisted EHD process to print high-resolution 2D patterns.

Additive manufacturing by the selective paste intrusion: Effect of the distance of the print nozzle to the particle bed on the print quality

Selective Paste Intrusion (SPI) is an additive manufacturing (AM) process in which thin layers of aggregates are selectively bonded by cement paste only where the structure is to be produced. In this way, concrete elements with complex geometries and structures can be created. Reinforcement is required to increase the flexural strength of the concrete elements and, thus, enable their applicability in practice. Integrating the reinforcement is a difficult task, particularly in the case of SPI, due to the layerwise printing method. Especially with respect to possible complex structures, the production of the reinforcement needs to be adapted to SPI, thereby offering a high degree of freedom. One concept for reinforcement integration is combining the two additive manufacturing processes, SPI and Wire and Arc Additive Manufacturing (WAAM). However, since the two processes serve different fields of application, their compatibility is not necessarily given. Ongoing investigations show that the temperatures caused by WAAM adversely affect both the cement paste rheology required for sufficient paste penetration into the particle bed and the overall concrete strength. This paper provides an overview of ongoing research focusing on different cooling strategies and their effects on the compressive strength of SPI-printed concrete parts.

Additive manufacturing of alumina refractories by binder jetting

In this work, refractory components based on alumina were produced by binder jetting using a large-scale 3D printer. The formulation contained several particle fractions up to a grain size of 3 mm, equal to the printer resolution. The binder system contained fine dead burnt magnesia, milled citric acid and reactive alumina, which were added to the aggregate mixture to create the powder bed. Deionized water was deposited from the printer's nozzles and triggered the binding reaction between the magnesia and citric acid. After 24 h, the printed samples were removed from the powder bed, dried and sintered at 1600 °C for 5 h. Reactive alumina contributed to the in situ creation of magnesium aluminate spinel at high temperature. The samples were characterized in terms of Young's modulus of elasticity, bending and compressive strength in 2 directions (parallel and perpendicular to the printing direction). The broken parts were used to investigate physical properties such as the open porosity and bulk density. The microstructure was studied by means of computed tomography. Finally, powder samples were used to determine the phase composition at different stages of production by means of XRD.

Nanocrystalline Cellulose to Reduce Superplasticizer Demand in 3D Printing of Cementitious Materials.

One challenge for 3D printing is that the mortar must flow easily through the printer nozzle, and after printing, it must develop compressive strength fast and high enough to support the layers on it. This requires an exact and difficult control of the superplasticizer (SP) dosing. Nanocrystalline cellulose (CNC) has gained significant interest as a rheological modifier of mortar by interacting with the various cement components. This research studied the potential of nanocrystalline cellulose (CNC) as a mortar aid for 3D printing and its interactions with SPs. Interactions of a CNC and SP with cement suspensions were investigated by means of monitoring the effect on cement dispersion (by monitoring the particle chord length distributions in real time) and their impact on mortar mechanical properties. Although cement dispersion was increased by both CNC and SP, only CNC prevented cement agglomeration when shearing was reduced. Furthermore, combining SP and CNC led to faster development of compressive strength and increased compressive strength up to 30% compared to mortar that had undergone a one-day curing process.

Fabrication of a microfluidic system with in situ-integrated microlens arrays using electrohydrodynamic jet printing

Microfluidic systems with integrated microlenses enhance cellular analysis and observation and have gained significant attention in the biomedical field. However, the integration and design of microlenses in microfluidic systems remain challenging. In this study, we utilize a high-precision electrohydrodynamic jet (E-jet) printing system for in-situ integration of microlens. By incorporating a tilting illumination observation module into the E-jet printing system, the print nozzle can be accurately positioned 10 μm above the microchannel bottom, thereby mitigating the edge effect of the microfluidic channels. We have developed a microfluidic system embedding microlens arrays (MLAs) that enable parallel, multichannel cell counting. The microfluidic system comprises nine channels, each featuring a 50 μm diameter microlens printed along the central axis. Using microlenses enables non-contact cell counting by detecting light-intensity changes. Simulating and optimizing the microfluidic channel size enable cells to align on the centerline of the channel and pass over the focal region of the microlens via inertial forces. As the cells flow through the microlens, the intensity of the focal spots decreases by approximately 50 %. The microfluidic cell-counting system can function independently or be integrated with other microfluidic systems as a unit, thus enhancing the single-cell operational and analytical capabilities of microfluidic systems.

Fabrication of flexible pressure sensor for human detection by direct-write printing concave surface

Flexible pressure sensor plays an important role in the field of human-computer interaction area due to its high flexibility and sensitivity. Convex surface of flexible electrodes provide an efficient way to enhance the sensitivity of flexible pressure sensors. However, facilely preparing controllable convex surface of flexible electrodes is still a challenge for obtaining high sensitive flexible pressure sensors. In this paper, direct-write print technique was utilized to prepare a concave structure surface with viscoelastic substrate, which could be used to prepare convex structure flexible electrode for fabricating highly sensitive flexible pressure sensors. Interaction between ink droplet and substrate was explored to generate a concave template, which could be controlled in spacing and diameter with printing spacing and nozzle diameter. Convex structure flexible surface could be prepared with the concave template, and then the convex structure flexible electrode could be realized with the evaporation of metallic silver on the surface. Furthermore, flexible pressure sensor was assembled with an interlocking structure by stacking two convex structure flexible electrodes in a face-to-face way, which could efficiently enhance flexibility and electrical property. The flexible pressure sensor presents a high sensitivity, a fast response/recovery time (<100 ms) and excellent flexibility (more than 10,000 cycles of bending), which could be applied in monitor physiological signals such as pulse detection, sound vibration, finger bending and so on. Therefore, this work provides an efficient method for preparing controllable structured surface, which has a great potential in the fabrication of flexible sensors, wearable electronics and energy devices.

3D printing of hydrogel composite systems: Recent advances in technology for tissue engineering.

Three-dimensional (3D) printing of hydrogels is now an attractive area of research due to its capability to fabricate intricate, complex and highly customizable scaffold structures that can support cell adhesion and promote cell infiltration for tissue engineering. However, pure hydrogels alone lack the necessary mechanical stability and are too easily degraded to be used as printing ink. To overcome this problem, significant progress has been made in the 3D printing of hydrogel composites with improved mechanical performance and biofunctionality. Herein, we provide a brief overview of existing hydrogel composite 3D printing techniques including laser based-3D printing, nozzle based-3D printing, and inkjet printer based-3D printing systems. Based on the type of additives, we will discuss four main hydrogel composite systems in this review: polymer- or hydrogel-hydrogel composites, particle-reinforced hydrogel composites, fiber-reinforced hydrogel composites, and anisotropic filler-reinforced hydrogel composites. Additionally, several emerging potential applications of hydrogel composites in the field of tissue engineering and their accompanying challenges are discussed in parallel.

Navigating the frontier: Additive Manufacturing’s role in synthesizing piezoelectric materials for flexible electronics

Additive manufacturing (AM) has significantly transformed the fabrication of functional materials, particularly in electronics and biomedical engineering. This study reviews stereolithography (SLA), selective laser sintering (SLS), fused deposition modeling (FDM), direct ink writing (DIW), and inkjet printing for flexible electronic applications. The review highlights SLA-based 3D printing’s better ability to optimize material compositions, printing procedures, and post-processing methods to improve material characteristics. Photosensitive materials and shrinkage-induced internal tensions seems to be its major constraint. Additionally, SLS 3D printing has improved composite materials' electrical, mechanical, and thermal properties. It has drawbacks including permeable structures and internal tensions. In FDM 3D printing, mechanical and electrical qualities are improved for piezoelectric sensor manufacture. Warping and nozzle blockage require additional study. DIW’s versatility in constructing complicated structures with increased features for energy harvesting and sensor development is also mentioned. We identify ink development and printer nozzle clogging issues. The review concludes that inkjet printing can provide a variety of materials for flexible electronics. Since it integrates the latest discoveries with technological developments, this study may help guide future research and promote innovation in the sector. Overall, additive manufacturing methods provide a new era of sensor technology by offering unrivalled flexibility and versatility.

Orientation of Liquid Crystalline Polymers after Filament Extrusion and after Passing through a 3D Printer Nozzle

Orientation of Liquid Crystalline Polymers after Filament Extrusion and after Passing through a 3D Printer Nozzle

Coaxial Electrohydrodynamic Bioprinting of Pre-vascularized Cell-laden Constructs for Tissue Engineering.

Recapitulating the vascular networks that maintain the delivery of nutrition, oxygen, and byproducts for the living cells within the three-dimensional (3D) tissue constructs is a challenging issue in the tissue-engineering area. Here, a novel coaxial electrohydrodynamic (EHD) bioprinting strategy is presented to fabricate thick pre-vascularized cell-laden constructs. The alginate and collagen/calcium chloride solution were utilized as the outer-layer and inner-layer bioink, respectively, in the coaxial printing nozzle to produce the core-sheath hydrogel filaments. The effect of process parameters (the feeding rate of alginate and collagen and the moving speed of the printing stage) on the size of core and sheath lines within the printed filaments was investigated. The core-sheath filaments were printed in the predefined pattern to fabricate lattice hydrogel with perfusable lumen structures. Endothelialized lumen structures were fabricated by culturing the core-sheath filaments with endothelial cells laden in the core collagen hydrogel. Multilayer core-sheath filaments were successfully printed into 3D porous hydrogel constructs with a thickness of more than 3 mm. Finally, 3D pre-vascularized cardiac constructs were successfully generated, indicating the efficacy of our strategy to engineer living tissues with complex vascular structures.