Printing Process Research Articles

Enhancing coloration performance and colour fastness of nano‐pigment ink‐jet‐printed blended fabrics through cationic and water‐repellent surface modification

AbstractThe coloration performance and colour fastness properties, crucial for industrial textile printing, depend on the spreading and fixation behaviour of ink‐jet droplets on porous fabrics. Current nano‐pigment‐based ink‐jet applications provide unstable results for these properties, especially for synthetic and blended fabrics. This study focuses on cellulose‐based blended fabrics as substrates to modify the wetting properties of fabrics through cationic and water‐repellent treatments, to improve the coloration performance and colour fastness systematically. The study conducted analytical experiments to analyse the surface element composition, ion potential and surface morphology of the fabrics. Differences in printing colour and pattern performance were attributed to the behaviour of ink droplet spreading on the fabric surface and inside the fabric, including wetting time, colourant distribution, and ring shape. The results indicate that ink droplet spreading on fabrics significantly influences printing pattern sharpness, including edge clarity and colour intensity, which can be improved through surface modification, including cationic and water repellent treatment. The use of blended fabrics treated with 1% cationic modifier and 0.05% fluorine‐containing water repellent resulted in effective suppression of droplet formation and significant enhancement of colour performance and fastness. Furthermore, as the ink droplet volume decreased from 5 to 1 μL, the coffee ring effect on the fabric treated with the water repellent agent gradually diminished, leading to improved printing sharpness during the printing process.

3D‐Printed In Situ Growth of Bilayer MOF Hydrogels for Accelerated Osteochondral Defect Repair

AbstractRepairing osteochondral (OC) defect presents a significant challenge due to the intricate structural requirements and the unpredictable differentiation pathways of bone marrow mesenchymal stem cells (BMSCs). To address this challenge, a novel biomimetic OC hydrogel scaffold is developed that features a structure of soft and hard components. This scaffold incorporates bilayer metal–organic frameworks (MOFs), specifically ZIF‐67 in the upper layer and ZIF‐8 in the lower layer, achieved through an in situ printing process. This configuration enables the spatial and temporal modulation of BMSC differentiation by controlling the release of Co2⁺ and Zn2⁺. The results demonstrate that the bilayer MOF hydrogels significantly outperform hydrogels that either lack MOFs or contain a single type of MOF in enhancing repair outcomes in rabbit models of knee OC defects. The improved regenerative efficacy is attributed to the distinct chondrogenic and osteogenic differentiation cues provided by the bilayer MOFs, effectively guiding BMSCs toward enhanced tissue regeneration. This customizable biomimetic OC hydrogel scaffold not only opens new avenues for innovative therapeutic strategies but also holds great promise for widespread clinical applications.

Trends in 3D Printing Processes for Biomedical Field: Opportunities and Challenges: An Editorial Retrospective

On 8 August 1984, Chuck Hull (Charles W [...]

Microfluidic Bubble-Templating Multinozzle 3D Printing for Preparations of Macroporous Hydrogels with Ordered Pores of Large Size Ranges.

A strategy for fabrication of macroporous hydrogels through 3D printing assisted by molding and multiple microfluidic bubble-templating nozzles is proposed here. This approach aims to address the challenges faced by methods for 3D printing macroporous hydrogels, such as difficulties in precisely controlling the spatial distribution of macropores, limited porosity, and low resolution of external boundaries due to the poor mechanical properties of hydrogel solutions as printing ink. In this method, fast-switching microfluidic bubble-templating nozzles of varying sizes allowed for precise control of target pore sizes over a wide range. Cavities of polydimethylsiloxane (PDMS) molds were used to define the overall external shape of the hydrogels and enhance the resolution of the boundaries. During the printing process, the laminar shear force generated by a coaxial microfluidic system generated microbubbles which were then injected into the PDMS mold cavities. The spatial distribution of the microbubble clusters within the cavities was controlled by a 3D motion module. Finally, macroporous hydrogels with a pore size range of 238-930 μm were fabricated while avoiding millimeter round corners on the boundaries. A control precision of pore sizes was about 60 μm. Most importantly, this strategy broke through the space occupancy limitations of pores in traditional 3D printing methods for macroporous hydrogels. The space occupancy of pores could reach a maximum of about 87% within a single layer.

Environmental Cationic Dye/Porous Silica Nanospheres for Printed Cotton Fabrics with Enhanced Coloration Performance.

The wastewater of printing and dyeing is difficult to treat due to the degradation resistance of dye and the use of massive chemicals, causing a threat to the ecosystem. Pigment printing of fabrics possesses great advantages like high efficiency and flexible production, but there are some challenges like the risk of color depth and hand feeling due to the large size of the pigment and poor adsorption of light. In order to improve the coloration ability of pigment, herein, a novel kind of cationic dye/porous silica nanospheres were prepared through the adsorption of methylene blue and rhodamine B onto electronegative porous silica nanospheres and applied in printing on woven cotton fabric. It was found that the nanospheres exhibited an average diameter, good color depth, hand feeling, and high image quality for pigment preparation. In comparison with dye-printed fabrics, fabrics with dye/WHMS show higher color depth, resulting from the lower visible light reflectance. Notably, the strong interaction between dyes and hydrophilic porous silica nanospheres (WHMS) facilitates the improvement of absorption efficiency and stability. Meanwhile, the printed fabrics with dye/WHMS demonstrate splendid color fastness. The dry/wet rubbing fastnesses are 4 and 3-4, respectively. Furthermore, dye/WHMS-printed cotton fabrics possess a satisfactory hand feeling and breathability. The consumptions of dye wastewater were reduced, and the printing process was simplified. We think that this work may provide a novel insight into printed textiles with enhanced color effects and alleviate the environmental impact of conventional textile coloration.

Effect of process variables on Ultimaker 2+ 3D FDM printed Tough PLA parts

ABSTRACT Fused Deposition Modeling (FDM) is pivotal in creating functional prototypes and end-use parts, with Tough PLA emerging as a favored material due to its durability. However, fine-tuning printing process variables for Tough PLA on the Ultimaker 2 + 3D printer remains challenging. This study employs Taguchi Grey relational analysis to optimize these process variables. L09 Taguchi’s systematic approach and Taguchi Grey Relational Grade Analysis (TGRGA) investigated Layer Thickness (LT), Infill Density (ID), and Nozzle Temperature (NT) at varying levels for which response variables such as Ultimate Tensile Strength (UTS), Average hardness (AH), and Surface Roughness (Ra) are evaluated. Utilizing Taguchi Grey Relational Grade Analysis (TGRGA), enhancements in ultimate tensile strength from 43.182 N/mm2 to 46.56 N/mm2, average hardness from 64 to 67, and Surface roughness from 8.60 µm to 8.35 µm are achieved. This study contributes to advancing additive manufacturing optimization, offering insights into refining Tough PLA part production on the Ultimaker 2 + 3D printer for bio implants like stent application.

Effect of the Ratio of Protein to Water on the Weak Gel Nonlinear Viscoelastic Behavior of Fish Myofibrillar Protein Paste from Alaska Pollock

The linear and nonlinear rheological behaviors of fish myofibrillar protein (FMP) paste with 75%, 82%, and 90% moisture content were evaluated using small-amplitude oscillatory shear (SAOS) and large-amplitude oscillatory shear (LAOS) tests. SAOS revealed pastes with 75% and 82% moisture exhibited solid-like behavior, characterized by higher storage modulus (G′) than loss modulus (G″), indicative of weak gel properties with a strong protein interaction. In contrast, the 90% moisture content showed more viscous behavior due to weakened protein–protein entanglements. The frequency exponent (n′ and n″) from the power law equation varied slightly (0.24 to 0.36), indicating limited sensitivity to changes in deformation rate during SAOS. LAOS tests revealed significant structural changes, with Lissajous–Bowditch curves revealing early nonlinearities at 10% strain for 90% moisture content. Decomposed Chebyshev coefficients (e3/e1, v3/v1, S, and T) indicated strain stiffening at lower strains for the 75% and 82% moisture pastes (i.e., < 50% strain for 75% and < 10% strain for 82%), transitioning to strain thinning at higher strains. Additionally, numerical model confirmed the predictability of the 3D printing process from the nonlinear rheological data, confirmed the suitability of the 75% and 82% moisture pastes for applications requiring structural integrity. These insights are essential for optimizing processing conditions in industrial applications. The findings suggest that the 75% and 82% moisture pastes are suitable for applications requiring structural integrity, while the 90% moisture paste is ideal for flow-based processes. These insights are essential for optimizing processing conditions in industrial applications.

Organic Ink Multi-Material 3D Printing of Sustainable Soft Systems.

Drawing inspiration from nature, soft materials are at the core of a transformation toward adaptive and responsive engineered systems, capable of conquering demanding terrain and safe when interacting with biological life. Despite recent advances in 3D printing of soft materials, researchers are still far from being able to print complex soft systems where a multitude of different components need to work together symbiotically. Closing this gap necessitates a platform that unites diverse materials into one synergetic process. Here, a multi-material printing system is presented, combining gelatin-based hydrogels with a new biodegradable support material. This organic ink maintains up to 60° overhang and is printable over gaps to structurally support the main biogel body, while triggered dissolution enables its selective removal and the formation of internal cavities. Therefore, the creation of vascular networks, tunable scaffolds, and embedded sensors within a single printing process becomes feasible. Furthermore, a perforation-resistant, joint-like vacuum actuator (VAc) is designed and 3D printed, capable of bending to angles up to 60° at fast response times down to 0.23 s. Combining these approaches in an efficient, streamlined fabrication process with biodegradable materials will unlock new sustainability dimensions for complex and durable soft systems.

Infrared on-site heating for material extrusion additive manufacturing of carbon fiber filled polyphenylene sulfide and its nano-graphene-reinforced alternatives

This study investigates the impact of infrared heating and annealing on the mechanical properties of carbon fiber-reinforced polyphenylene sulfide (CF-PPS) and graphene nanoplatelet (GNP)-reinforced CF-PPS composites in Material extrusion (MEX) additive manufacturing. GNP/CF-PPS composites are prepared by mechanically mixing CF-PPS plastic particles with GNP particles and subjecting them to infrared heating and annealing treatments during the three-dimensional (3D) printing process. Three-point bending tests assess the mechanical properties of the samples. The results reveal that the 0.03 wt.% GNP/CF-PPS sample, subjected to infrared heating followed by annealing, exhibits a 30% increase in bending strength compared to pure CF-PPS, demonstrating that the combined treatment significantly enhances mechanical performance. Microscopy observations using a Keyence VH7000 digital optical microscope and a scanning electron microscope (SEM) confirm that GNP addition and infrared irradiation lead to reduced surface roughness and fewer fracture cross-sectional pores. The interlayer bonding improves notably, indicating enhanced internal density and structural stability. Furthermore, differential scanning calorimetry analysis shows a 20% increase in crystallinity for heat-treated samples, contributing to better interlaminar bonding and reduced temperature gradients during printing. Finite element simulations using MATLAB and ABAQUS software corroborate these findings, demonstrating that infrared heating proves more effective than varying GNP content alone in reducing deformation, residual stress, and temperature differences during the MEX process. These results provide valuable insights into improving the mechanical properties and stability of MEX-manufactured large-dimensional composite materials through optimized thermal management.

Viscosity measurements of selected lunar regolith simulants

Abstract In the context of evaluating lunar construction options, this study focuses on characterizing the viscosities and glass transition properties of lunar regolith simulants to support the development of additive manufacturing processes using molten regolith. Employing the modular TUBS lunar regolith simulant system, we measured the viscosities of different simulants through high-temperature experiments conducted between 1,051 °C and 1,490 °C using Concentric Cylinder viscometry in air. Additionally, Differential Scanning Calorimetry (DSC) was utilized to evaluate the glass transition temperatures, which were in the range between 689 °C and 815 °C. The measured viscosity data were parameterized by the Vogel—Fulcher—Tammann (VFT) equation, adept at describing the viscosities and related properties of silicate liquids. The measured viscosities were compared with the predicted values of six viscosity models. It was shown that the model by Sehlke and Whittington predicts the viscosities of the tested lunar regolith simulants at superliquidus temperatures best, whereby no model adequately predicts viscosities at the glass transition temperature, indicating a need for further research in this area. We infer that 3D printing technologies based on molten lunar regolith, are viscosity-wise best constrained to highland regions. The reduced environment on the Moon influences the 3D printing process in a positive manner.

Peridynamic Framework to Model Additive Manufacturing Processes

AbstractThe study presents a framework for analyzing Additive Manufacturing processes within the Peridynamics (PD) software PeriLab. This framewor k employs a mesh‐free, point‐based numerical approach to approximate the continuum PD equations. Implemented within this framework are thermal, thermo‐mechanical, and simple additive models. These models have been validated against analytical solutions, Finite Element (FE) models, and Peridigm simulations. To leverage the PD mesh‐free implementation, the study introduces a novel boundary detection algorithm. This algorithm is essential because the outer surface area may change during the manufacturing process. It operates without requiring surface or topology information, relying instead on the comparison of neighborhood volume to sphere volume. Additionally, the study introduces a wrapper that generates the mesh necessary for simulating the printing process, based on the G‐code machine input path. Finally, the study presents a comprehensive analysis of an L‐shaped profile utilizing the developed features, comparing the results with those obtained from an Abaqus solution.

A Study of Fit and Friction Force as a Function of the Printing Process for FFF 3D-Printed Piston–Cylinder Assembly

Current 3D printing processes for polymer material extrusion are limited in their accuracy in terms of dimension, form, and position. For precise results, post-processing is recommended, like with assembled parts such as pistons and cylinders wherein axial mobility is desired with low friction force and limited radial play. When no post-processing step of the printed parts is accomplished, the fit and the friction force behavior are strongly dependent on the process performances. This paper presents a study on parameters of significance and their effects on sliding and running fits as well as their friction forces for fused filament fabrication of such assemblies. A series of experiments were performed with multiple factors and levels, including the position or layout of printed objects, their layer thickness, the material used, the use of aligned or random seam, and the printer type. Piston–cylinder pairs were printed, measured, assembled, and tested using a tensile test frame. A mathematical model was developed to describe the oscillating friction force behavior observed. This study presents the feasibility and limitations of producing piston–cylinder assemblies with reduced play and friction when using appropriate conditions. It also provides recommendations to obtain and better control a desired running and sliding fit.

Tunable Lotus Leaf Effect by Three-Dimensionally Printed Stretchable Objects.

Adjustable wettability is important for various fields, such as droplet manipulation and controlled surface adhesion. Herein, we present high-resolution 3D stretchable structures with tunable superhydrophobicity, fabricated by a stereolithography-based printing process. The printing compositions comprise nonfluorinated monomers based on silicone urethane with dispersed hydrophobic silica particles. 3D lotus-like structures were designed and printed, having microsize pillars located at the external surfaces, with controlled dimensions and interspacing. The design of the pillars and the presence of the hydrophobic silica particles resulted in superhydrophobicity due to the surface structuring and entrapment of air between the pillars. The best structures display a contact angle of 153.3° ± 1.3° and rolling angle of 3.3° ± 0.5°, and their self-cleaning, water repellency, and buoyancy are demonstrated. The durability of the structure over time, water immersion, and heat exposure were tested, confirming the preservation of superhydrophobicity under these conditions. Upon stretching the surfaces, the interpillar distances change, thus enabling tuning the wetting properties and achieving good control over the contact and rolling angles, while the stretching-induced superhydrophobicity is reversible. This approach can expand the potential applications of superhydrophobic soft materials to fields requiring control over the wetting properties, including soft robotics, biomedical devices, and stretchable electronics.

Enhanced color density from high-viscosity inkjet inks

AbstractInkjet printing inks are typically limited to low viscosities, employing highly dilute inks with low pigment loading compared with inks for other printing processes. This reduces color intensity, limits productivity, and requires higher drying energy. This study compares standard-viscosity graphic inkjet inks (~13 mPa.s shear viscosity) with higher-viscosity inkjet inks (~60 mPa.s), traditionally considered outside the normal jetting range, for print outcomes on corrugated cardboard with both white coated and brown uncoated liners. Higher-viscosity inks imparted greater color density to the print; this was assessed as being due to both the inherently higher viscosity of the ink reducing penetration into the substrate and the higher pigment loading capable of being contained within these inks. While standard-viscosity inks tended to plateau in color intensity as ink coverage was increased, higher-viscosity inks could increase in intensity throughout the entire coverage range on coated white liner. This effect was dependent on the substrate, with the coated white liner exhibiting up to a 67% increase in maximum color density but the uncoated brown liner showing up to a 13% increase. It is envisaged that wider adoption of higher-viscosity inks can increase both color intensity and printing speed, thus making inkjet more competitive with conventional printing processes.

Investigation of support structure configurations for selective laser melting of In718

The Selective Laser Melting (SLM), as a widely used metallic Additive manufacturing (AM) process, relies heavily on support structures. This study investigated the impact of different support structure configurations on the quality of In718 samples fabricated through SLM. On the basis of a comprehensive review of existing support structures configurations from the literature, three typical configurations: block, cone, and lattice, were designed to support cantilever parts for performance comparison. A coupled thermo-structural finite element simulation using ANSYS was performed to evaluate the temperature, deformation, and thermal stress evolution during the printing process of the three supported cantilever structures. The residual stress and deformation of the printed In718 cantilevers with different support structures were measured for validation. The results showed that block support exhibits the best strength and heat dissipation capability, making it the most effective support configuration for the SLM of In718 material. This research provides a fundamental procedure for evaluating the supporting performances among various support structures for the SLM process.

Hybrid heating in the fused filament fabrication process

AbstractAltering the heating regime of the polymer during the fused filament fabrication (FFF) process can lead to changes in both the behaviour of the polymer and the characteristics of the printed product. This study proposes replacing the traditional resistive heating system with two hybrid systems that introduce an additional temperature of 120–160 °C: one combining resistive and hot air jet heating, and the other combining resistive and infrared radiation heating. The samples printed using these hybrid systems were analysed using differential scanning calorimetry (DSC) and visually inspected. Commercial ABS and PLA filaments were used in the experimental programme. A model to evaluate the polymer’s melting during the printing process was proposed and experimentally validated. Visual testing revealed that the printed lattice structure had smaller voids, characterised by depositions that were flattened rather than circular in cross-section due to the extended time in a viscous/partially molten state. The elongation viscosity and storage modulus decreased by approximately 10%, with a slightly smaller decrease observed for the infrared radiation heat source. The glass transition temperature remained unchanged, and the molecular mobility was not affected by the additional heat. Similarly, the energy required for crystal formation was unaffected by the supplementary heat. The mechanical behaviour of the printed pieces during compression tests was also influenced by the addition of a second heat source. For both materials, a decrease in deformability was observed as the temperature of the hot air jet increased.

Investigation of formation, microstructure and hardness of Ti-6Al-4V single tracks via Joule-fused filament additive manufacturing

Purpose This paper aims to investigate a novel additive manufacturing (AM) method for titanium alloy using Joule heat as the single heat source to melt TC4 wire, which intends to provide a new low-power, low-cost solution for the processing of titanium alloys. Design/methodology/approach When current flows through the wire and the substrate, Joule heat will be generated to melt the wire and join the wire with the substrate. By stacking the wire layer by layer, finally a part can be formed. The cross-sectional morphology, microstructure and hardness of TC4 single track deposits formed by Joule heat melting wire AM were investigated by various characterization methods. Findings The melting width and melting penetration decreased with the increase of printing speeds. There is no obvious change in single track morphology with the change of printing pressures. The melting width and melting penetration increased with the increase of printing currents. The observation of the internal microstructure of a single track reveals a decrease in grain size as printing speeds increase. The average hardness of the single track was about 363 HV, which is comparable to the hardness of the parts fabricated by selective laser melting process. The printing power is less than 300 W, which is lower than other AM processes. Originality/value This paper provides a novel solution for the processing of titanium alloy parts. Compared with other expensive energy sources, this work only uses an ordinary DC power supply as the energy source. The printing process is simple and the cost is low. The power is much lower than other AM processes.

Preparation of Purpurin-Fe2+ Complex Natural Dye and Its Printing Performance on Silk Fabrics.

In order to shorten the process of textile printing with natural dyes, develop new methods, and improve the color fastness and quality of printed products, this study presents a novel approach by synthesizing a natural complex dye through the interaction between purpurin and Fe2+ ions, resulting in a compound named purpurin-Fe2+ (P-Fe). This synthesized complex dye was meticulously characterized using state-of-the-art analytical techniques, including Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-Vis) spectrophotometry, and scanning electron microscopy energy-dispersive spectroscopy (EDS). The characterization confirmed the successful complexation of purpurin with Fe2+ ions. The prepared complex dye P-Fe was used for the printing of silk fabric. The optimized printing process involves steaming at a temperature of 100 °C for a duration of 20 min. In comparison to fabrics printed using direct dyes, the K/S values of the fabric printed with the P-Fe complex showed a significant enhancement, with all color fastness ratings achieving grade four. Furthermore, the proportion of metal elements on the white background of the printed fabric was found to be less than 0.180%, and the level of whiteness was above 50. The application of the P-Fe dye in silk fabric printing not only streamlines the printing process but also enhances the depth and speed of the printed color, effectively addressing the issue of color transfer onto a white background, which is commonly associated with natural dyes.

Preparation of Si3N4f/Si3N4 wave-transparent composites by vat photopolymerization combined with chemical vapor infiltration

The strategic combination of material selection, forming processes, and densification techniques is crucial for optimizing the performance of wave-transparent materials in extreme environments. This study is the first time to prepare Si3N4f/Si3N4 wave-transparent composites using a combination of vat photopolymerization (VPP) 3D printing and chemical vapor infiltration (CVI) processes. The effects of Si3N4f content on slurry preparation, green part printing, and final performance were systematically investigated. The addition of Si3N4f significantly enhanced the toughness of Si3N4 ceramics. Apart from their inherent toughening mechanisms, the "chimeric pinning" effect of the fibers contributes to increased interlayer bonding strength, thereby favorably impacting the mechanical properties. Combining VPP 3D printing and CVI processes resulted in Si3N4f/Si3N4 composites with a linear shrinkage rate within 1%, essentially achieving near-net shaping. Additionally, the composites exhibited excellent mechanical and dielectric properties, with a flexural strength of 76.2MPa, fracture toughness of 4.24MPa·m1/2, a dielectric constant of 4, and a dielectric loss tangent of 0.01. This study leverages the high strength and toughness advantages of Si3N4f and employs VPP 3D printing combined with CVI to achieve the objectives of lightweight, high transmittance, and near-net shaping. It provides theoretical support and experimental validation for designing and manufacturing wave-transparent materials.

Applicability of 3D concrete printing technology in building construction with different architectural design decisions in housing

3D Printing (3DP) technology, one of the layered production methodologies where design and construction configurations can be made with increasing digitalization and Industry 4.0, is one of the leading techniques of the period. 3D Concrete Printing (3DCP) also comes to the fore in the construction industry. The study aims to observe the impact of architectural design decisions on the 3DCP process by developing controlled and consistent design alternatives. Architectural designs developed with different geometric forms in the housing function were subjected to digital planning, 3DCP preparation, and 3DCP prototype final product stages. In the integration of design and 3D concrete printing (3DCP), two key aspects were investigated: (i) the impact of different geometric forms (square, rectangle, hexagon, octagon, circle, and ellipse) on the buildability performance of 3D-printed structures, and (ii) how variations in design details influence printing time, material consumption, cost, and the feasibility of mass production in architectural applications. For the 3DCP process, 3D-printable cementitious mixture was developed, and a 3D printer with dimensions of 100 x 100 x 40 centimeters was used. The results obtained during the printing process were analyzed in comparison with the building evaluation parameters. As a result, the house with circular geometry showed the optimum behavior according to the parameters of buildability, cost, and mass producibility. The circle geometric form provides a 4.2% advantage over the octagon in terms of buildability, a 16.6% advantage over the ellipse in terms of cost, and a 20% advantage over the ellipse in terms of mass producibility.