3D Printing Process Research Articles

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

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

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.

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.

Machine Learning in 3D and 4D Printing of Polymer Composites: A Review

The emergence of 3D and 4D printing has transformed the field of polymer composites, facilitating the fabrication of complex structures. As these manufacturing techniques continue to progress, the integration of machine learning (ML) is widely utilized to enhance aspects of these processes. This includes optimizing material properties, refining process parameters, predicting performance outcomes, and enabling real-time monitoring. This paper aims to provide an overview of the recent applications of ML in the 3D and 4D printing of polymer composites. By highlighting the intersection of these technologies, this paper seeks to identify existing trends and challenges, and outline future directions.

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.

4D printing of smart scaffolds for bone regeneration: a systematic review.


As a novel emerging technology, four-dimensional (4D) printing allows 3D-printed materials to change over time. This systematic review is conducted to evaluate the purpose, materials, physiomechanical, and biological properties of 4D-printed scaffolds used for bone tissue engineering.
Method and materials:
An electronic search was conducted following the PRISMA 2020 guidelines in PubMed, Scopus, Web of Science, and Google Scholar online databases limited to English articles until April 2024. Studies in which scaffolds were fabricated through 3D printing methods responding to external stimulation were included. The quality of in vitro and in vivo studies was evaluated through the modified CONSORT checklist and SYRCLE's risk of bias tool.
Results:
The full text of 57 studies were reviewed, and 15 studies met the inclusion criteria. According to the analyzed studies, most scaffolds responded to temperature changes showing shape memory effect. Polyurethane (PU) and poly(lactic acid) (PLA) were the most common shape memory polymers, and the most common fabrication method used was Fused Deposition Modeling (FDM).
Conclusion:
A comprehensive systematic review of the studies from the past 10 years demonstrated several findings: 1) Shape memory, drug delivery, and shape morphing are three general purposes of 4D printing for bone regeneration. 2) Smart materials used for 4D printing mostly consist of shape memory polymers. 3) Temperature changes account for the majority of stimulation used for 4D printing. 4) incorporating 4D printing principles does not have a negative impact on the physiomechanical properties of the designed scaffold. 5) The 4D-printed scaffolds show a higher osteogenic differentiation capacity than their identical 3D-printed structures in terms of bone regeneration.&#xD.

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.

Insight into the “synergistic-relaxation effects” in amorphous polymer: Thermodynamic modeling, multiphysics simulation and application in 4D printing

Insight into the “synergistic-relaxation effects” in amorphous polymer: Thermodynamic modeling, multiphysics simulation and application in 4D printing

3D printing of cordierite glass-ceramics

Compared to traditional ceramic materials, glass-ceramics can also exhibit superior properties and are now widely used in cutting-edge national defense industries technology, aerospace, electronics, construction, and other fields. In this study, it is for the first time reported that novel photopolymerization 3D printable slurries using cordierite glass ceramic powder were prepared. The effects of slurry properties and printing process parameters on the warpage of the printed samples were studied. Cordierite glass-ceramic parts fabricated using photopolymerization 3D printing and heat treatment processes were studied to evaluate the effects of sintering parameters on the properties of the samples. The obtained additively manufactured cordierite glass-ceramics exhibit excellent microstructural and mechanical properties, with a maximum bending strength of 181 MPa, an increase of 95.66 % compared to that of the previously reported 3D printed cordierite ceramics. The underlying mechanisms of the glass and ceramic phase characteristics influence the density and the mechanical properties during and after the courses of sintering were also investigated and unveiled in detail. This study provides a viable method for manufacturing complex-shaped cordierite glass-ceramic components using 3D printing.

3D Printed Personalized Colon-targeted Tablets: A Novel Approach in Ulcerative Colitis Management.

Ulcerative colitis (UC) and Crohn's disease (CD) are two types of idiopathic inflammatory bowel disease (IBD) that are increasing in frequency and incidence worldwide, particularly in highly industrialized countries. Conventional tablets struggle to effectively deliver anti-inflammatory drugs since the inflammation is localized in different areas of the colon in each patient. The goal of 3D printing technology in pharmaceutics is to create personalized drug delivery systems (DDS) that are tailored to each individual's specific needs. This review provides an overview of existing 3D printing processes, with a focus on extrusion-based technologies, which have received the most attention. Personalized pharmaceutical products offer numerous benefits to patients worldwide, and 3D printing technology is becoming more affordable every day. Custom manufacturing of 3D printed tablets provides innovative ideas for developing a tailored colon DDS. In the future, 3D printing could be used to manufacture personalized tablets for UC patients based on the location of inflammation in the colon, resulting in improved therapeutic outcomes and a better quality of life.

3D printed feathers with embedded aerodynamic sensing

Bird flight is often characterized by outstanding aerodynamic efficiency, agility and adaptivity in dynamic conditions. Feathers play an integral role in facilitating these aspects of performance, and the benefits feathers provide largely derive from their intricate and hierarchical structures. Although research has been attempted on developing membrane-type artificial feathers for bio-inspired aircraft and micro air vehicles (MAVs), fabricating anatomically accurate artificial feathers to fully exploit the advantages of feathers has not been achieved. Here, we present our 3D printed artificial feathers consisting of hierarchical vane structures with feature dimensions spanning from 10-2to 102mm, which have remarkable structural, mechanical and aerodynamic resemblance to natural feathers. The multi-step, multi-scale 3D printing process used in this work can provide scalability for the fabrication of artificial feathers tailored to the specific size requirements of aircraft wings. Moreover, we provide the printed feathers with embedded aerodynamic sensing ability through the integration of customized piezoresistive and piezoelectric transducers for strain and vibration measurements, respectively. Hence, the 3D printed feather transducers combine the aerodynamic advantages from the hierarchical feather structure design with additional aerodynamic sensing capabilities, which can be utilized in future biomechanical studies on birds and can contribute to advancements in high-performance adaptive MAVs.

Smart curtains using 4D printing technology to protect people with Special needs due to temperature differences

Smart curtains using 4D printing technology to protect people with Special needs due to temperature differences

Innovative Hybrid Nanocomposites in 3D Printing for Functional Applications: A Review.

3D printing has garnered significant attention across academia and industry due to its capability to design and fabricate complex architectures. Applications such as those requiring intricate geometries or custom designs, including footwear, healthcare, energy storage, and electronics applications, greatly benefit from exploiting 3D printing processes. Despite the recent advancement of structural 3D printing, its use in functional devices remains limited, requiring the need for the development of functional materials suitable for 3D printing in device fabrication. In this review, we briefly introduce various 3D printing techniques, including material extrusion and vat polymerization, and highlight the recent advances in 3D printing for energy and biomedical devices. A summary of future perspectives in this area is also presented. By highlighting recent developments and addressing key challenges, this review aims to inspire future directions in the development of functional devices.

Application of Poly(lactic Acid) Composites in the Automotive Sector: A Critical Review.

The introduction of bio-based matrices in automotive applications would, in principle, increase their sustainability and, in case the use of secondary raw materials is also involved, even result in reduced resource depletion. The bio-based polymer composite matrix that has been mainly brought forward towards industrial application is poly(lactic acid) (PLA), which has often been proposed as the replacement for matrices based on polyolefins in fields such as packaging and short-term commodities since, in general, it matches the needs for conventional thermoplastic production processes. The passage to the automotive sector is not obvious, though: problems affecting durability, the relation with water and the environment, together with the requirement for outstanding mechanical and impact performance appear very stringent. On the other hand, PLA has obtained durable success in additive manufacturing as a competitor for acrylonitrile butadiene styrene (ABS). Also, the perspective for 3D and 4D printing does not appear to be confined to bare prototyping. These contrasting pieces of evidence indicate the necessity to provide more insight into the possible development of PLA use in the automotive industry, also considering the pressure for the combined use of more sustainable reinforcement types in automotive composites, such as natural fibers.

Triaxial compressive behavior of 3D printed PE fiber-reinforced ultra-high performance concrete

The layered deposition process of 3D concrete printing can lead to reduced mechanical properties at the interfaces between filaments. To address this limitation, external confinement devices, such as fiber-reinforced polymer (FRP) wrapping, have been proposed to enhance the strength of 3D-printed concrete concrete. Achieving this requires a solid understanding of the triaxial mechanical performance of 3D-printed concrete. This study presents an experimental investigation of the triaxial compressive behavior of 3D-printed PE fiber-reinforced ultra-high performance concrete (3DP-PEUHPC). A total of 16 pairs of concrete cubes were prepared, including mold-cast and 3D-printed specimens, and subjected to uniaxial and triaxial compression tests. The results revealed that the 3D-printed specimens exhibited either column-type or diagonal shear failures under triaxial compression. Weak bonding was observed at both filament-fusion and layer-fusion interfaces, with these weaker bonding interfaces, particularly when aligned parallel to the axial load, showing susceptibility to stress concentration and crack initiation. This led to a reduction in load-bearing capacity of the 3D-printed specimens compared to the mold-cast specimens. Importantly, as confining stresses increase, the difference in compressive strength between 3D-printed and mold-cast specimens decreases, highlighting the effectiveness of confinement in mitigating the directional weaknesses inherent in 3D-printed concrete. This paper also presents a modified model for predicting the axial stress-strain relationship of 3DP-PEUHPC under confinement, providing insights into the mechanism of FRP confinement on the compressive strength of 3D-printed concrete structures.

Printing the Future Layer by Layer: A Comprehensive Exploration of Additive Manufacturing in the Era of Industry 4.0

In the era of Industry 4.0, 3D printing, or additive manufacturing (AM), has revolutionized product design and manufacturing across various sectors. This review explores the evolution of 3D printing technology and its impact on industrial innovation, highlighting advancements in aeronautics, the automotive industry, and biomedicine. Various AM processes, such as binder jetting, direct energy deposition, and powder bed fusion, and materials like metals, polymers, ceramics, and composites, are discussed. Innovations like high-speed sintering, continuous liquid interface production, and bioprinting demonstrate ongoing advancements. The potential of 3D printing in personalized medical applications is emphasized due to its flexibility in geometry and materials. Despite progress, challenges like standardization, material quality, recycling, sustainability, and economic feasibility hinder widespread adoption. Overcoming these challenges is crucial for optimizing 3D printing technologies, ensuring high-quality, efficient, and affordable production. The review also addresses the future prospects of 4D and 5D printing technologies and their potential applications in various industries. This overview underscores 3D printing’s role in shaping the future of manufacturing within the context of Industry 5.0, emphasizing human–machine collaboration and sustainability.

Precision 4D Printing of Multifunctional Olive Oil‐Based Acrylate Photo‐resin for Biomedical Applications

AbstractSince the advent of 3D printing technology, a significant effort has been made to develop new 3D printable materials. Despite the recent progress in the field of 3D printing, the limited availability of photoactive resins has motivated continuous research endeavors to develop novel photoresins with multifunctional capabilities. Herein a biobased photoresin derived is reported from modified olive oil, designed for high‐resolution solvent‐free 4D printing with multifunctional capabilities. The physicochemical properties of the printed polymers are fine‐tuned using acrylic acid as a diluent cum comonomer. The mechanical properties of the printed polymers are similar to various soft tissues, such as ligaments, articular cartilage, and soft collagenous bone, showcasing its potential for soft tissue engineering applications. While the excellent temperature‐responsive shape memory 4D attributes coupled with exceptional antimicrobial properties toward gram‐negative and gram‐positive bacteria highlight the multifunctional nature of the printed polymers. Moreover, the printed polymers exhibited outstanding hemocompatibility and good cytocompatibility toward mouse fibroblast cells, suggesting their potential soft tissue engineering applications. In sum, the newly developed biobased resin can be employed to minimize the environmental impact of additive manufacturing while being competitive with existing fossil‐based photoresins, thereby meeting the growing demand for advanced photoresins with superior high‐resolution printing and smart properties for biomedical applications.

4D Printing of Ultra‐High Performance Shape Memory Polymer for Space Applications

Developing thermoplastic polyimide (TPI), capable of handling space conditions, through 4D printing is challenging due to its high melting temperature and inherent viscosity. This study presents 4D printing of TPI for shape memory investigation under repetitive cycles for the first time, exploring its potential for self‐deployable hinges in space devices. 4D‐printed TPI exhibits outstanding shape memory effect (SME) with shape fixity (Rf) up to 100% and shape recovery (Rr) of 100% in first cycle. Rf is noted to be increasing up to third cycle and then fixed to 100% up to tenth cycle, while Rr shows a decreasing trend in subsequent cycle with a drop of 37% in tenth cycle. Moreover, it exhibits extremely high glass‐transition temperature, Tg = 263.10 °C, degradation temperature, Td = 520 °C, and storage modulus of 1600 MPa. Among existing high‐performance (HP) and conventional shape memory polymers (SMPs), 3D‐printed TPI exhibits superior performance. Tg of the TPI is found to be 66.52%, 107.16%, and 62.41%, higher than existing HP‐SMPs, polyether ether ketone (Tg = 158 °C), polyamide (Tg = 127 °C), and polyether ketone ketone (Tg = 162 °C), respectively. This investigation reveals a novel characteristic, the SME, of 4D‐printed TPI with ultra‐high Tg and Td, demonstrating suitability for self‐deployable hinges, contributing to materials engineering and 4D printing.

Experimental study on mechanical properties of 3D Printed layered rock like materials

Layered rocks are prevalent in the Earth’s crust and are frequently encountered in underground engineering construction. Due to their pronounced anisotropy, the deformation and failure mechanism of layered rock are complex. Laboratory tests are an effective way to study these mechanisms. However, natural layered rocks present challenges, such as difficult sampling and large discreteness. Additionally, current methods for creating layered rock models are often costly or lack precision, limiting research into their mechanical properties. In this study, a 3D printing process using wet material extrusion was adopted, with a wide range of material options and low production costs. Five layered model samples with bedding dip angles of 0°, 30°, 45°, 60° and 90° were printed using this method. Uniaxial compression tests were conducted, supplemented by digital image correlation (DIC) to capture detailed stress–strain data and failure patterns. The results demonstrate that the mechanical properties of the 3D-printed samples closely resemble those of natural layered rocks and exhibit significant anisotropy. This approach presents a new cost-effective method for studying the mechanical behavior of layered rock.

Closed-Loop Recycling of 3D-Printed Wood-PLA Composite Parts: Effects on Mechanical and Structural Properties via Fused Filament Fabrication.

This study investigated the closed-loop recycling of 3D-printed wood fiber (WF)-filled polylactic acid (PLA) composites via fused filament fabrication (FFF). The WF-PLA composites (WPCs) were extruded into WPC filaments (WPCfs) to produce FFF-printed WPC parts (WPCps). The printed WPCps were reprocessed three times via extrusion and 3D-printing processes. The tensile properties and impact strengths of the WPCfs and WPCps were determined. To further investigate the impact of closed-loop recycling on the surface morphology, crystallinity, and molecular weight of WPCfs, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC), respectively, were used. After closed-loop recycling, the surface morphology of the WPCfs became smoother, and a decrease in the pore sizes was observed; however, the tensile properties (tensile strength and elongation at break) deteriorated. With increasing numbers of recycling iterations, the molecular weight of the PLA matrix decreased, while an increase in crystallinity was observed due to the recrystallization of the low-molecular-weight PLA molecules after recycling. According to the SEM images of the recycled WPCps, their layer heights were inconsistent, and the layers were rough and discontinuous. Additionally, the color difference (ΔE*) of the recycled WPCps significantly increased. Compared with those of the WPCps after recycling them only once, the tensile strength, elongation at break, and impact strength of the WPCps noticeably decreased after recycling them twice. Considering the changes in various properties of the WPCfs and WPCps, the FFF-printed WPC parts can be reprocessed only once through 3D printing.